process of photosynthesis

ENCYCLOPEDIC ENTRY

Photosynthesis.

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar.

Loading ...

Learning materials, instructional links.

Photosynthesis (Google doc)

Most life on Earth depends on photosynthesis .The process is carried out by plants, algae, and some types of bacteria, which capture energy from sunlight to produce oxygen (O 2 ) and chemical energy stored in glucose (a sugar). Herbivores then obtain this energy by eating plants, and carnivores obtain it by eating herbivores.

The process

During photosynthesis, plants take in carbon dioxide (CO 2 ) and water (H 2 O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air, and stores energy within the glucose molecules.

Chlorophyll

Inside the plant cell are small organelles called chloroplasts , which store the energy of sunlight. Within the thylakoid membranes of the chloroplast is a light-absorbing pigment called chlorophyll , which is responsible for giving the plant its green color. During photosynthesis , chlorophyll absorbs energy from blue- and red-light waves, and reflects green-light waves, making the plant appear green.

Light-dependent Reactions vs. Light-independent Reactions

While there are many steps behind the process of photosynthesis, it can be broken down into two major stages: light-dependent reactions and light-independent reactions. The light-dependent reaction takes place within the thylakoid membrane and requires a steady stream of sunlight, hence the name light- dependent reaction. The chlorophyll absorbs energy from the light waves, which is converted into chemical energy in the form of the molecules ATP and NADPH . The light-independent stage, also known as the Calvin cycle , takes place in the stroma , the space between the thylakoid membranes and the chloroplast membranes, and does not require light, hence the name light- independent reaction. During this stage, energy from the ATP and NADPH molecules is used to assemble carbohydrate molecules, like glucose, from carbon dioxide.

C3 and C4 Photosynthesis

Not all forms of photosynthesis are created equal, however. There are different types of photosynthesis, including C3 photosynthesis and C4 photosynthesis. C3 photosynthesis is used by the majority of plants. It involves producing a three-carbon compound called 3-phosphoglyceric acid during the Calvin Cycle, which goes on to become glucose. C4 photosynthesis, on the other hand, produces a four-carbon intermediate compound, which splits into carbon dioxide and a three-carbon compound during the Calvin Cycle. A benefit of C4 photosynthesis is that by producing higher levels of carbon, it allows plants to thrive in environments without much light or water. The National Geographic Society is making this content available under a Creative Commons CC-BY-NC-SA license . The License excludes the National Geographic Logo (meaning the words National Geographic + the Yellow Border Logo) and any images that are included as part of each content piece. For clarity the Logo and images may not be removed, altered, or changed in any way.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Production Managers

Program specialists, last updated.

June 21, 2024

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

Biology Article

Photosynthesis

Photosynthesis is a process by which phototrophs convert light energy into chemical energy, which is later used to fuel cellular activities. The chemical energy is stored in the form of sugars, which are created from water and carbon dioxide.

Table of Contents

What is Photosynthesis?
Site of photosynthesis

What Is Photosynthesis in Biology?

The word “ photosynthesis ” is derived from the Greek words phōs (pronounced: “fos”) and σύνθεσις (pronounced: “synthesis “) Phōs means “light” and σύνθεσις means, “combining together.” This means “ combining together with the help of light .”

Photosynthesis also applies to other organisms besides green plants. These include several prokaryotes such as cyanobacteria, purple bacteria and green sulfur bacteria. These organisms exhibit photosynthesis just like green plants.The glucose produced during photosynthesis is then used to fuel various cellular activities. The by-product of this physio-chemical process is oxygen.

A visual representation of the photosynthesis reaction

Photosynthesis is also used by algae to convert solar energy into chemical energy. Oxygen is liberated as a by-product and light is considered as a major factor to complete the process of photosynthesis.
Photosynthesis occurs when plants use light energy to convert carbon dioxide and water into glucose and oxygen. Leaves contain microscopic cellular organelles known as chloroplasts.
Each chloroplast contains a green-coloured pigment called chlorophyll. Light energy is absorbed by chlorophyll molecules whereas carbon dioxide and oxygen enter through the tiny pores of stomata located in the epidermis of leaves.
Another by-product of photosynthesis is sugars such as glucose and fructose.
These sugars are then sent to the roots, stems, leaves, fruits, flowers and seeds. In other words, these sugars are used by the plants as an energy source, which helps them to grow. These sugar molecules then combine with each other to form more complex carbohydrates like cellulose and starch. The cellulose is considered as the structural material that is used in plant cell walls.

Where Does This Process Occur?

Chloroplasts are the sites of photosynthesis in plants and blue-green algae. All green parts of a plant, including the green stems, green leaves, and sepals – floral parts comprise of chloroplasts – green colour plastids. These cell organelles are present only in plant cells and are located within the mesophyll cells of leaves.

Photosynthesis process requires several factors such as:

Increased light intensity results in a higher rate of photosynthesis. On the other hand, low light intensity results in a lower rate of photosynthesis. Higher concentration of carbon dioxide helps in increasing the rate of photosynthesis. Usually, carbon dioxide in the range of 300 – 400 PPM is adequate for photosynthesis. For efficient execution of photosynthesis, it is important to have a temperature range between 25° to 35° C. As water is an important factor in photosynthesis, its deficiency can lead to problems in the intake of carbon dioxide. The scarcity of water leads to the refusal of stomatal opening to retain the amount of water they have stored inside. : Industrial pollutants and other particulates may settle on the leaf surface. This can block the pores of stomata which makes it difficult to take in carbon dioxide.

Also Read: Photosynthesis Early Experiments

Photosynthesis Equation

Photosynthesis reaction involves two reactants, carbon dioxide and water. These two reactants yield two products, namely, oxygen and glucose. Hence, the photosynthesis reaction is considered to be an endothermic reaction. Following is the photosynthesis formula:

+ 6H O —> C H O + 6O

Unlike plants, certain bacteria that perform photosynthesis do not produce oxygen as the by-product of photosynthesis. Such bacteria are called anoxygenic photosynthetic bacteria. The bacteria that do produce oxygen as a by-product of photosynthesis are called oxygenic photosynthetic bacteria.

There are four different types of pigments present in leaves:

Structure Of Chlorophyll

The structure of Chlorophyll consists of 4 nitrogen atoms that surround a magnesium atom. A hydrocarbon tail is also present. Pictured above is chlorophyll- f, which is more effective in near-infrared light than chlorophyll- a

Chlorophyll is a green pigment found in the chloroplasts of the plant cell and in the mesosomes of cyanobacteria. This green colour pigment plays a vital role in the process of photosynthesis by permitting plants to absorb energy from sunlight. Chlorophyll is a mixture of chlorophyll- a and chlorophyll- b .Besides green plants, other organisms that perform photosynthesis contain various other forms of chlorophyll such as chlorophyll- c1 , chlorophyll- c2 , chlorophyll- d and chlorophyll- f .

Process Of Photosynthesis

At the cellular level, the photosynthesis process takes place in cell organelles called chloroplasts. These organelles contain a green-coloured pigment called chlorophyll, which is responsible for the characteristic green colouration of the leaves.

As already stated, photosynthesis occurs in the leaves and the specialized cell organelles responsible for this process is called the chloroplast. Structurally, a leaf comprises a petiole, epidermis and a lamina. The lamina is used for absorption of sunlight and carbon dioxide during photosynthesis.

Structure of Chloroplast. Note the presence of the thylakoid

“Photosynthesis Steps:”

During the process of photosynthesis, carbon dioxide enters through the stomata, water is absorbed by the root hairs from the soil and is carried to the leaves through the xylem vessels. Chlorophyll absorbs the light energy from the sun to split water molecules into hydrogen and oxygen.
The hydrogen from water molecules and carbon dioxide absorbed from the air are used in the production of glucose. Furthermore, oxygen is liberated out into the atmosphere through the leaves as a waste product.
Glucose is a source of food for plants that provide energy for growth and development , while the rest is stored in the roots, leaves and fruits, for their later use.
Pigments are other fundamental cellular components of photosynthesis. They are the molecules that impart colour and they absorb light at some specific wavelength and reflect back the unabsorbed light. All green plants mainly contain chlorophyll a, chlorophyll b and carotenoids which are present in the thylakoids of chloroplasts. It is primarily used to capture light energy. Chlorophyll-a is the main pigment.

The process of photosynthesis occurs in two stages:

Light-dependent reaction or light reaction
Light independent reaction or dark reaction

Stages of Photosynthesis in Plants depicting the two phases – Light reaction and Dark reaction

Light Reaction of Photosynthesis (or) Light-dependent Reaction

Photosynthesis begins with the light reaction which is carried out only during the day in the presence of sunlight. In plants, the light-dependent reaction takes place in the thylakoid membranes of chloroplasts.
The Grana, membrane-bound sacs like structures present inside the thylakoid functions by gathering light and is called photosystems.
These photosystems have large complexes of pigment and proteins molecules present within the plant cells, which play the primary role during the process of light reactions of photosynthesis.
There are two types of photosystems: photosystem I and photosystem II.
Under the light-dependent reactions, the light energy is converted to ATP and NADPH, which are used in the second phase of photosynthesis.
During the light reactions, ATP and NADPH are generated by two electron-transport chains, water is used and oxygen is produced.

The chemical equation in the light reaction of photosynthesis can be reduced to:

2H 2 O + 2NADP+ + 3ADP + 3Pi → O 2 + 2NADPH + 3ATP

Dark Reaction of Photosynthesis (or) Light-independent Reaction

Dark reaction is also called carbon-fixing reaction.
It is a light-independent process in which sugar molecules are formed from the water and carbon dioxide molecules.
The dark reaction occurs in the stroma of the chloroplast where they utilize the NADPH and ATP products of the light reaction.
Plants capture the carbon dioxide from the atmosphere through stomata and proceed to the Calvin photosynthesis cycle.
In the Calvin cycle , the ATP and NADPH formed during light reaction drive the reaction and convert 6 molecules of carbon dioxide into one sugar molecule or glucose.

The chemical equation for the dark reaction can be reduced to:

3CO 2 + 6 NADPH + 5H 2 O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi

* G3P – glyceraldehyde-3-phosphate

Calvin photosynthesis Cycle (Dark Reaction)

Also Read: Cyclic And Non-Cyclic Photophosphorylation

Importance of Photosynthesis

Photosynthesis is essential for the existence of all life on earth. It serves a crucial role in the food chain – the plants create their food using this process, thereby, forming the primary producers.
Photosynthesis is also responsible for the production of oxygen – which is needed by most organisms for their survival.

Frequently Asked Questions

1. what is photosynthesis explain the process of photosynthesis., 2. what is the significance of photosynthesis, 3. list out the factors influencing photosynthesis., 4. what are the different stages of photosynthesis, 5. what is the calvin cycle, 6. write down the photosynthesis equation..

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

Visit BYJU’S for all Biology related queries and study materials

Your result is as below

Request OTP on Voice Call

BIOLOGY Related Links

Register with BYJU'S & Download Free PDFs

It’s a wonderful world — and universe — out there.

Come explore with us!

Science News Explores

Explainer: how photosynthesis works.

Plants make sugar and oxygen with the power of water, carbon dioxide and sunlight

green leaves lit up from behind with sunlight

Green plants take in light from the sun and turn water and carbon dioxide into the oxygen we breathe and the sugars we eat.

Jeja/E+/Getty Images

Let the light shine in

When light hits a plant’s leaves, it shines on chloroplasts and into their thylakoid membranes. Those membranes are filled with chlorophyll , a green pigment. This pigment absorbs light energy. Light travels as electromagnetic waves . The wavelength — distance between waves — determines energy level. Some of those wavelengths are visible to us as the colors we see . If a molecule, such as chlorophyll, has the right shape, it can absorb the energy from some wavelengths of light.

Chlorophyll can absorb light we see as blue and red. That’s why we see plants as green. Green is the wavelength plants reflect, not the color they absorb.

While light travels as a wave, it also can be a particle called a photon . Photons have no mass. They do, however, have a small amount of light energy.

When a photon of light from the sun bounces into a leaf, its energy excites a chlorophyll molecule. That photon starts a process that splits a molecule of water. The oxygen atom that splits off from the water instantly bonds with another, creating a molecule of oxygen, or O 2 . The chemical reaction also produces a molecule called ATP and another molecule called NADPH. Both of these allow a cell to store energy. The ATP and NADPH also will take part in the synthesis part of photosynthesis.

Notice that the light reaction makes no sugar. Instead, it supplies energy — stored in the ATP and NADPH — that gets plugged into the Calvin cycle. This is where sugar is made.

But the light reaction does produce something we use: oxygen. All the oxygen we breathe is the result of this step in photosynthesis, carried out by plants and algae (which are not plants ) the world over.

Give me some sugar

The next step takes the energy from the light reaction and applies it to a process called the Calvin cycle. The cycle is named for Melvin Calvin, the man who discovered it.

The Calvin cycle is sometimes also called the dark reaction because none of its steps require light. But it still happens during the day. That’s because it needs the energy produced by the light reaction that comes before it.

While the light reaction takes place in the thylakoid membranes, the ATP and NADPH it produces end up in the stroma. This is the space inside the chloroplast but outside the thylakoid membranes.

The Calvin cycle has four major steps:

carbon fixation : Here, the plant brings in CO 2 and attaches it to another carbon molecule, using rubisco. This is an enzyme , or chemical that makes reactions move faster. This step is so important that rubisco is the most common protein in a chloroplast — and on Earth. Rubisco attaches the carbon in CO 2 to a five-carbon molecule called ribulose 1,5-bisphosphate (or RuBP). This creates a six-carbon molecule, which immediately splits into two chemicals, each with three carbons.
reduction : The ATP and NADPH from the light reaction pop in and transform the two three-carbon molecules into two small sugar molecules. The sugar molecules are called G3P. That’s short for glyceraldehyde 3-phosphate (GLIH- sur-AAL-duh-hide 3-FOS-fayt).
carbohydrate formation : Some of that G3P leaves the cycle to be converted into bigger sugars such as glucose (C 6 H 12 O 6 ).
regeneration : With more ATP from the continuing light reaction, leftover G3P picks up two more carbons to become RuBP. This RuBP pairs up with rubisco again. They are now ready to start the Calvin cycle again when the next molecule of CO 2 arrives.

At the end of photosynthesis, a plant ends up with glucose (C 6 H 12 O 6 ), oxygen (O 2 ) and water (H 2 O). The glucose molecule goes on to bigger things. It can become part of a long-chain molecule, such as cellulose; that’s the chemical that makes up cell walls. Plants also can store the energy packed in a glucose molecule within larger starch molecules. They can even put the glucose into other sugars — such as fructose — to make a plant’s fruit sweet.

All of these molecules are carbohydrates — chemicals containing carbon, oxygen and hydrogen. (CarbOHydrate makes it easy to remember.) The plant uses the bonds in these chemicals to store energy. But we use the these chemicals too. Carbohydrates are an important part of the foods we eat, particularly grains, potatoes, fruits and vegetables.

Many flowers and ferns lure in ants as bodyguards

A new-to-science "fairy lantern" is seen poking just above dead leaves. A bright yellow is ringed by brownish tentacle-like parts that stick out almost perpendicular. This all sits atop a slug-shaped part with orange stripes, which is attached to a thinner, longer pale stem.

This squid-like ‘fairy lantern’ plant is new to science

More than a dozen plastic containers dot the greenish-brown vegetation in the foreground of this Arctic tundra site in Sweden. A body of water and mountains shrouded in mist are visible in the background.

Microbes in the Arctic may be releasing more climate-warming gases

Gene editing may help rice better withstand climate change

A bee flies toward a yellow buttercup flower.

Flowers may electrically detect bees buzzing nearby

Let’s learn about photosynthesis

a coastal landslide drags a river of water and soil down a hill from farmland to the beach

Experiment: Can plants stop soil erosion?

On hot summer days, this thistle stays cool to the touch

COVID-19 Tracker
Biochemistry
Anatomy & Physiology
Microbiology
Neuroscience
Animal Kingdom
NGSS High School
Latest News
Editors’ Picks
Weekly Digest
Quotes about Biology

Photosynthesis

Reviewed by: BD Editors

Photosynthesis Definition

Photosynthesis is the biochemical pathway which converts the energy of light into the bonds of glucose molecules. The process of photosynthesis occurs in two steps. In the first step, energy from light is stored in the bonds of adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide phosphate (NADPH). These two energy-storing cofactors are then used in the second step of photosynthesis to produce organic molecules by combining carbon molecules derived from carbon dioxide (CO 2 ). The second step of photosynthesis is known as the Calvin Cycle. These organic molecules can then be used by mitochondria to produce ATP, or they can be combined to form glucose, sucrose, and other carbohydrates. The chemical equation for the entire process can be seen below.

Photosynthesis Equation

Above is the overall reaction for photosynthesis. Using the energy from light and the hydrogens and electrons from water, the plant combines the carbons found in carbon dioxide into more complex molecules. While a 3-carbon molecule is the direct result of photosynthesis, glucose is simply two of these molecules combined and is often represented as the direct result of photosynthesis due to glucose being a foundational molecule in many cellular systems. You will also notice that 6 gaseous oxygen molecules are produced, as a by-produce. The plant can use this oxygen in its mitochondria during oxidative phosphorylation . While some of the oxygen is used for this purpose, a large portion is expelled into the atmosphere and allows us to breathe and undergo our own oxidative phosphorylation, on sugar molecules derived from plants. You will also notice that this equation shows water on both sides. That is because 12 water molecules are split during the light reactions, while 6 new molecules are produced during and after the Calvin cycle. While this is the general equation for the entire process, there are many individual reactions which contribute to this pathway.

Stages of Photosynthesis

The light reactions.

The light reactions happen in the thylakoid membranes of the chloroplasts of plant cells. The thylakoids have densely packed protein and enzyme clusters known as photosystems . There are two of these systems, which work in conjunction with each other to remove electrons and hydrogens from water and transfer them to the cofactors ADP and NADP + . These photosystems were named in the order of which they were discovered, which is opposite of how electrons flow through them. As seen in the image below, electrons excited by light energy flow first through photosystem II (PSII), and then through photosystem I (PSI) as they create NADPH. ATP is created by the protein ATP synthase , which uses the build-up of hydrogen atoms to drive the addition of phosphate groups to ADP.

The entire system works as follows. A photosystem is comprised of various proteins that surround and connect a series of pigment molecules . Pigments are molecules that absorb various photons, allowing their electrons to become excited. Chlorophyll a is the main pigment used in these systems, and collects the final energy transfer before releasing an electron. Photosystem II starts this process of electrons by using the light energy to split a water molecule, which releases the hydrogen while siphoning off the electrons. The electrons are then passed through plastoquinone, an enzyme complex that releases more hydrogens into the thylakoid space . The electrons then flow through a cytochrome complex and plastocyanin to reach photosystem I. These three complexes form an electron transport chain , much like the one seen in mitochondria. Photosystem I then uses these electrons to drive the reduction of NADP + to NADPH. The additional ATP made during the light reactions comes from ATP synthase, which uses the large gradient of hydrogen molecules to drive the formation of ATP.

The Calvin Cycle

With its electron carriers NADPH and ATP all loaded up with electrons, the plant is now ready to create storable energy. This happens during the Calvin Cycle , which is very similar to the citric acid cycle seen in mitochondria. However, the citric acid cycle creates ATP other electron carriers from 3-carbon molecules, while the Calvin cycle produces these products with the use of NADPH and ATP. The cycle has 3 phases, as seen in the graphic below.

During the first phase, a carbon is added to a 5-carbon sugar, creating an unstable 6-carbon sugar. In phase two, this sugar is reduced into two stable 3-carbon sugar molecules. Some of these molecules can be used in other metabolic pathways, and are exported. The rest remain to continue cycling through the Calvin cycle. During the third phase, the five-carbon sugar is regenerated to start the process over again. The Calvin cycle occurs in the stroma of a chloroplast. While not considered part of the Calvin cycle, these products can be used to create a variety of sugars and structural molecules.

Products of Photosynthesis

The direct products of the light reactions and the Calvin cycle are 3-phosphoglycerate and G3P, two different forms of a 3-carbon sugar molecule. Two of these molecules combined equals one glucose molecule, the product seen in the photosynthesis equation. While this is the main food source for plants and animals, these 3-carbon skeletons can be combined into many different forms. A structural form worth note is cellulose , and extremely strong fibrous material made essentially of strings of glucose. Besides sugars and sugar-based molecules, oxygen is the other main product of photosynthesis. Oxygen created from photosynthesis fuels every respiring organism on the planet.

Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Scott, M. P., Bretscher, A., . . . Matsudaira, P. (2008). Molecular Cell Biology 6th. ed . New York: W.H. Freeman and Company. Nelson, D. L., & Cox, M. M. (2008). Principles of Biochemistry . New York: W.H. Freeman and Company.

Cite This Article

Subscribe to our newsletter, privacy policy, terms of service, scholarship, latest posts, white blood cell, t cell immunity, satellite cells, embryonic stem cells, popular topics, hydrochloric acid, scientific method, water cycle.

Why Does Water Expand When It Freezes
Gold Foil Experiment
Faraday Cage
Oil Drop Experiment
Magnetic Monopole
Why Do Fireflies Light Up
Types of Blood Cells With Their Structure, and Functions
The Main Parts of a Plant With Their Functions
Parts of a Flower With Their Structure and Functions
Parts of a Leaf With Their Structure and Functions
Why Does Ice Float on Water
Why Does Oil Float on Water
How Do Clouds Form
What Causes Lightning
How are Diamonds Made
Types of Meteorites
Types of Volcanoes
Types of Rocks

Photosynthesis

What is photosynthesis.

It is the process by which green plants, algae, and certain bacteria convert light energy from the sun into chemical energy that is used to make glucose. The word ‘photosynthesis’ is derived from the Greek word phōs, meaning ‘light’ and synthesis meaning ‘combining together.’

Jan Ingenhousz, the Dutch-born British physician and scientist, discovered the process of photosynthesis.

Where does Photosynthesis Occur

Photosynthesis takes place mainly in the leaves of green plants and also in the stems of herbaceous plants as they also contain chlorophyll. Sometimes it also occurs in roots that contain chlorophyll like in water chestnut and Heart-leaved moonseed. Apart from plants, photosynthesis is also found to occur in blue-green algae.

What Happens During Photosynthesis

It involves a chemical reaction where water, carbon dioxide, chlorophyll, and solar energy are utilized as raw materials (inputs) to produce glucose, oxygen, and water (outputs).

Stages of the Process

Photosynthesis occurs in two stages:

1) The Light-dependent Reaction

Takes place in the thylakoid membranes of chloroplasts only during the day in the presence of sunlight
High-energy phosphate molecules adenosine triphosphate ( ATP ) and the reducing agent NADPH are produced with the help of electron transport chain

2) The Light-independent or Dark Reaction ( Calvin cycle )

Takes place in the stroma of chloroplast in the absence of light that helps to fix carbon
ATP and NADPH produced in the light reaction are utilized along with carbon dioxide to produce sugar in the form of glucose

Factors Affecting the Rate of Photosynthesis

Intensity of Light: The higher intensity of light increases the rate of photosynthesis
Temperature: Warmer the temperature, higher the rate of photosynthesis. The rate is highest between the temperatures of 25° to 35° C, after which it starts to decrease
Concentration of Carbon dioxide: Higher concentration of carbon dioxide increases the rate of photosynthesis until it reaches a certain point, beyond which no further effects are found

Although all the above factors together interact to affect the rate of photosynthesis, each of them individually is also capable of directly influencing the process without the other factors and thus called limiting factors.

Importance of Photosynthesis

It serves two main purposes that are essential to support life on earth:

Producing food for organisms that depend on others for their nutrition such as humans along with all other animals
Synthesizing oxygen by replacing carbon dioxide in the atmosphere

Ans. Photosynthesis is an endothermic reaction because it absorbs the heat of the sun to carry out the process.

Ans. The oxygen in photosynthesis comes from splitting the water molecules.

Ans. Chlorophyll is the main light-absorbing pigment in photosynthesis.

Ans. The role of water is to provide oxygen in the form of oxygen gas to the atmosphere.

Ans. Sunlight is the source of energy that drives photosynthesis.

Ans. The easiest way to measure the rate of photosynthesis is to quantify the carbon dioxide or oxygen levels using a data logger. The rate of photosynthesis can also be measured by determining the increase in the plant ’s biomass (weight).

Ans. Photosynthesis is an energy-requiring process occurring only in green plants, algae, and certain bacteria that utilizes carbon dioxide and water to produce food in the form of carbohydrates. In contrast, cellular respiration is an energy-releasing process found in all living organisms where oxygen and glucose are utilized to produce carbon dioxide and water.

Ans. Glucose produced in photosynthesis is used in cellular respiration to make ATP.

Article was last reviewed on Tuesday, April 21, 2020

Join our Newsletter

Fill your E-mail Address

Related Worksheets

This page has been archived and is no longer updated

Photosynthetic Cells

Cells get nutrients from their environment, but where do those nutrients come from? Virtually all organic material on Earth has been produced by cells that convert energy from the Sun into energy-containing macromolecules. This process, called photosynthesis, is essential to the global carbon cycle and organisms that conduct photosynthesis represent the lowest level in most food chains (Figure 1).

What Is Photosynthesis? Why Is it Important?

Most living things depend on photosynthetic cells to manufacture the complex organic molecules they require as a source of energy. Photosynthetic cells are quite diverse and include cells found in green plants, phytoplankton, and cyanobacteria. During the process of photosynthesis, cells use carbon dioxide and energy from the Sun to make sugar molecules and oxygen. These sugar molecules are the basis for more complex molecules made by the photosynthetic cell, such as glucose. Then, via respiration processes, cells use oxygen and glucose to synthesize energy-rich carrier molecules, such as ATP, and carbon dioxide is produced as a waste product. Therefore, the synthesis of glucose and its breakdown by cells are opposing processes.

However, photosynthesis doesn't just drive the carbon cycle — it also creates the oxygen necessary for respiring organisms. Interestingly, although green plants contribute much of the oxygen in the air we breathe, phytoplankton and cyanobacteria in the world's oceans are thought to produce between one-third and one-half of atmospheric oxygen on Earth.

What Cells and Organelles Are Involved in Photosynthesis?

Chlorophyll A is the major pigment used in photosynthesis, but there are several types of chlorophyll and numerous other pigments that respond to light, including red, brown, and blue pigments. These other pigments may help channel light energy to chlorophyll A or protect the cell from photo-damage. For example, the photosynthetic protists called dinoflagellates, which are responsible for the "red tides" that often prompt warnings against eating shellfish, contain a variety of light-sensitive pigments, including both chlorophyll and the red pigments responsible for their dramatic coloration.

What Are the Steps of Photosynthesis?

Photosynthesis consists of both light-dependent reactions and light-independent reactions . In plants, the so-called "light" reactions occur within the chloroplast thylakoids, where the aforementioned chlorophyll pigments reside. When light energy reaches the pigment molecules, it energizes the electrons within them, and these electrons are shunted to an electron transport chain in the thylakoid membrane. Every step in the electron transport chain then brings each electron to a lower energy state and harnesses its energy by producing ATP and NADPH. Meanwhile, each chlorophyll molecule replaces its lost electron with an electron from water; this process essentially splits water molecules to produce oxygen (Figure 5).

Once the light reactions have occurred, the light-independent or "dark" reactions take place in the chloroplast stroma. During this process, also known as carbon fixation, energy from the ATP and NADPH molecules generated by the light reactions drives a chemical pathway that uses the carbon in carbon dioxide (from the atmosphere) to build a three-carbon sugar called glyceraldehyde-3-phosphate (G3P). Cells then use G3P to build a wide variety of other sugars (such as glucose) and organic molecules. Many of these interconversions occur outside the chloroplast, following the transport of G3P from the stroma. The products of these reactions are then transported to other parts of the cell, including the mitochondria, where they are broken down to make more energy carrier molecules to satisfy the metabolic demands of the cell. In plants, some sugar molecules are stored as sucrose or starch.

This page appears in the following eBook

Topic rooms within Cell Biology

Within this Subject (25)

Basic (25)

Visual Browse

Microbe Notes

Photosynthesis: Equation, Steps, Process, Diagram

Photosynthesis is defined as the process, utilized by green plants and photosynthetic bacteria, where electromagnetic radiation is converted into chemical energy and uses light energy to convert carbon dioxide and water into carbohydrates and oxygen.

The carbohydrates formed from photosynthesis provide not only the necessary energy form the energy transfer within ecosystems, but also the carbon molecules to make a wide array of biomolecules.
Photosynthesis is a light-driven oxidation-reduction reaction where the energy from the light is used to oxidize water, releasing oxygen gas and hydrogen ions, followed by the transfer of electrons to carbon dioxide, reducing it to organic molecules.
Photosynthetic organisms are called autotrophs because they can synthesize chemical fuels such as glucose from carbon dioxide and water by utilizing sunlight as an energy source.
Other organisms that obtain energy from other organisms also ultimately depend on autotrophs for energy.
One of the essential requirements for photosynthesis is the green pigment ‘chlorophyll’ which is present in the chloroplasts of green plants and some bacteria.
The pigment is essential for ‘capturing’ sunlight which then drives the overall process of photosynthesis.

Table of Contents

Interesting Science Videos

Photosynthesis equations/reactions/formula

The process of photosynthesis differs in green plants and sulfur bacteria.
In plants, water is utilized along with carbon dioxide to release glucose and oxygen molecules.
In the case of sulfur bacteria, hydrogen sulfide is utilized along with carbon dioxide to release carbohydrates, sulfur, and water molecules.

Oxygenic Photosynthesis

The overall reaction of photosynthesis in plants is as follows:

Carbon dioxide + Water + solar energy → Glucose + Oxygen

6CO 2 + 6H 2 O + solar energy → C 6 H 12 O 6 + 6O 2

Carbon dioxide + Water + solar energy → Glucose + Oxygen + Water

6CO 2 + 12H 2 O+ solar energy → C 6 H 12 O 6 + 6O 2 + 6H 2 O

Anoxygenic Photosynthesis

The overall reaction of photosynthesis in sulfur bacteria is as follows:

CO 2 + 2H 2 S + light energy → (CH 2 O) + H 2 O + 2S

Video Animation: Photosynthesis (Crash Course)

Photosynthetic pigments

Photosynthetic pigments are the molecules involved in absorbing electromagnetic radiation, transferring the energy of the absorbed photons to the reaction center, resulting in photochemical reactions in the organisms capable of photosynthesis.
The molecules of photosynthetic pigments are quite ubiquitous and are always composed of chlorophylls and carotenoids.
In addition to chlorophyll, photosynthetic systems also contain another pigment, pheophytin (bacteriopheophytin in bacteria), which plays a crucial role in the transfer of electrons in photosynthetic systems.
Moreover, other pigments can be found in particular photosynthetic systems, such as xanthophylls in plants.

Image Source: Simply Science .

Chlorophyll

Chlorophyll is the pigment molecule, which is the principal photoreceptor in the chloroplasts of most green plants.
Chlorophylls consist of a porphyrin ring, which is bounded to an ion Mg 2+ , attached to a phytol chain.
Chlorophylls are very effective photoreceptors because they contain networks of alternating single and double bonds.
In chlorophyll, the electrons are not localized to a particular atomic nucleus and consequently can more readily absorb light energy.
In addition, chlorophylls also have solid absorption bands in the visible region of the spectrum.
Chlorophylls are found either in the cytoplasmic membranes of photosynthetic bacteria, or thylakoid membranes inside plant chloroplasts.

Bacteriorhodopsin

Bacteriorhodopsin is another class of photosynthetic pigment that exists only in halobacteria.
It is composed of a protein attached to a retinal prosthetic group.
This pigment is responsible for the absorption of light photons, leading to a conformational change in the protein, which results in the expulsion of the protons from the cell.

Phycobilins

Cyanobacteria and red algae employ phycobilins such as phycoerythrobilin and phycocyanobilin as their light-harvesting pigments.
These open-chain tetrapyrroles have the extended polyene system found in chlorophylls, but not their cyclic structure or central Mg 2+ .
Phycobilins are covalently linked to specific binding proteins, forming phycobiliproteins, which associate in highly ordered complexes called phycobilisomes that constitute the primary light-harvesting structures in these microorganisms.

Carotenoids

In addition to chlorophylls, thylakoid membranes contain secondary light-absorbing pigments, or accessory pigments, called carotenoids.
Carotenoids may be yellow, red, or purple. The most important are β -carotene, which is a red-orange isoprenoid, and the yellow carotenoid lutein.
The carotenoid pigments absorb light at wavelengths not absorbed by the chlorophylls and thus are supplementary light receptors.

Factors affecting photosynthesis

Blackman formulated the Law of limiting factors while studying the factors affecting the rate of photosynthesis. This Law states that the rate of a physiological process will be limited by the factor which is in the shortest supply. In the same way, the rate of photosynthesis is also affected by a number of factors, which are namely;

As the intensity of light increases, the rate of light-dependent reactions of photosynthesis and in turn, the rate of photosynthesis increases.
With increased light intensity, the number of photons falling on a leaf also increases. As a result, more chlorophyll molecules are ionized, and more ATPs and NADH are generated.
After a point, however, the rate of photosynthesis remains constant as the light intensity increases. At this point, photosynthesis is limited by some other factors.
Besides, the wavelength of light also affects the rate of photosynthesis.
Different photosynthetic systems absorb light energy more effectively at different wavelengths.

Carbon dioxide

An increase in the concentration of carbon dioxide increases the rate at which carbon is incorporated into carbohydrates in the light-independent reactions of photosynthesis.
Thus, increasing the concentration of carbon dioxide in the atmosphere rapidly increases the rate of photosynthesis up to a point after which it is limited by some other factors.

Temperature

The light-independent reactions of photosynthesis are affected by changes in temperature as they are catalyzed by enzymes, whereas the light-dependent reactions are not.
The rate of the reactions increases as the enzymes reach their optimum temperature, after which the rate begins to decrease as the enzymes tend to denature.

Process/ Steps of Photosynthesis

The overall process of photosynthesis can be objectively divided into four steps/ process:

1. Absorption of light

The first step in photosynthesis is the absorption of light by chlorophylls that are attached to the proteins in the thylakoids of chloroplasts.
The light energy absorbed is then used to remove electrons from an electron donor like water, forming oxygen.
The electrons are further transferred to a primary electron acceptor, quinine (Q) which is similar to CoQ in the electron transfer chain.

2. Electron Transfer

The electrons are now further transferred from the primary electron acceptor through a chain of electron transfer molecules present in the thylakoid membrane to the final electron acceptor, which is usually NADP + .
As the electrons are transferred through the membrane, protons are pumped out of the membrane, resulting in the proton gradient across the membrane.

3. Generation of ATP

The movement of protons from the thylakoid lumen to the stroma through the F 0 F 1 complex results in the generation of ATP from ADP and Pi.
This step is identical to the step of the generation of ATP in the electron transport chain .

4. Carbon Fixation

The NADP and ATP generated in steps 2 and 3 provide energy, and the electrons drive the process of reducing carbon into six-carbon sugar molecules.
The first three steps of photosynthesis are directly dependent on light energy and are thus, called light reactions, whereas the reactions in this step are independent of light and thus are termed dark reactions.

Types/ Stages/ Parts of photosynthesis

Figure: Photosynthesis takes place in two stages: light-dependent reactions and the Calvin cycle. Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH. The Calvin cycle, which takes place in the stroma, uses energy derived from these compounds to make GA3P from CO 2 . Image Source: OpenStax (Rice University) .

Photosynthesis is divided into two stages based on the utilization of light energy:

1. Light-dependent reactions

The light-dependent reactions of photosynthesis only take place when the plants/ bacteria are illuminated.
In the light-dependent reactions, chlorophyll and other pigments of photosynthetic cells absorb light energy and conserve it as ATP and NADPH while simultaneously, evolving O 2 gas.
In the light-dependent reactions of photosynthesis, the chlorophyll absorbs high energy, short-wavelength light, which excites the electrons present inside the thylakoid membrane.
The excitation of electrons now initiates the transformation of light energy into chemical energy.
The light reactions take in two photosystems that are present in the thylakoid of chloroplasts.

Figure: Light-dependent reactions of photosynthesis in the thylakoid membrane of plant cells. Image Source: Wikipedia (Somepics) .

Photosystem II

Photosystem II is a group of proteins and pigments that work together to absorb light energy and transfer electrons through a chain of molecules until it finally reaches an electron acceptor.
Photosystem II has a pair of chlorophyll molecules, also known as P680 as the molecules best absorb light of the wavelength 680 nm.
The P680 donates a pair of electrons after absorbing light energy, resulting in an oxidized form of P680.
Finally, an enzyme catalyzes the splitting of a water molecule into two electrons, two hydrogen ion, and oxygen molecules.
This pair of electrons then are transferred to P680, causing it to return to its initial stage.

Photosystem I

Photosystem I is a similar complex like photosystem II except for that photosystem I have a pair of chlorophyll molecules known as P700 as they best absorb the wavelength of 700 nm.
As photosystem I absorb light energy, it also becomes excited and transfers electrons.
The now oxidized form of P700 then accepts an electron from photosystem II, restring back to its initial stage.
The electrons from photosystem I are then passed in a series of redox reactions through the protein ferredoxin.
The electrons finally reach NADP + , reducing them to NADPH.

2 H 2 O + 2 NADP + + 3 ADP + 3 P i + light → 2 NADPH + 2 H + + 3 ATP + O 2

Video Animation: The Light Reactions of Photosynthesis (Ricochet Science)

2. Light independent reactions (Calvin cycle)

Light independent reactions of photosynthesis are anabolic reactions that lead to the formation of a sex-carbon compound, glucose in plants. The reactions in this stage are also termed dark reactions as they are not directly dependent on the light energy but do require the products formed from the light reactions.

Figure: Overview of the Calvin cycle pathway. Image Source: Wikipedia (Mike Jones) .

This stage consists of 3 further steps that lead to carbon fixation/ assimilation.

Step 1: Fixation of CO 2 into 3-phosphoglycerate

In this step, one CO 2 molecule is covalently attached to the five-carbon compound ribulose 1,5-biphosphate catalyzed by the enzyme ribulose 1,5-biphosphate carboxylase, also called rubisco.
The attachment results in the formation of an unstable six-carbon compound that is then cleaved to form two molecules of 3-phosphoglycerate.

Step 2: Conversion of 3-phosphoglycerate to glyceraldehydes 3-phosphate

The 3-phosphoglycerate formed in step 1 is converted to glyceraldehyde 3-phosphate by two separate reactions.
At first, enzyme 3-phosphoglycerate kinase present in the stroma catalyzes the transfer of a phosphoryl group from ATP to 3-phosphoglycerate, yielding 1,3-bisphosphoglycerate.
Next, NADPH donates electrons in a reaction catalyzed by the chloroplast-specific isozyme of glyceraldehyde 3-phosphate dehydrogenase, producing glyceraldehyde 3-phosphate and phosphate (Pi).
Most of the glyceraldehyde 3-phosphate thus produced is used to regenerate ribulose 1,5-bisphosphate.
The rest of the glyceraldehyde is either converted to starch in the chloroplast and stored for later use or is exported to the cytosol and converted to sucrose for transport to growing regions of the plant.

Step 3: Regeneration of ribulose 1,5-biphosphate from triose phosphates

The three-carbon compounds formed in the previous steps are then converted into the five-carbon compound, ribulose 1,5-biphosphate through a series of transformations with intermediates of three-, four,-, five-, six-, and seven-carbon sugar.
As the first molecules in the process, if regenerated, this stage of photosynthesis results in a cycle (Calvin cycle).

3 CO 2 + 9 ATP + 6 NADPH + 6 H + → glyceraldehyde-3-phosphate (G3P) + 9 ADP + 8 P i + 6 NADP + + 3 H 2 O

A G3P molecule contains three fixed carbon atoms, so it takes two G3Ps to build a six-carbon glucose molecule. It would take six turns of the cycle to produce one molecule of glucose.

Video Animation: The Calvin Cycle (Ricochet Science)

Products of Photosynthesis

The outcomes of light-dependent reactions of photosynthesis are:

The products of light-independent reactions (Calvin cycle) of photosynthesis are:

glyceraldehyde-3-phosphate (G3P) / Glucose (carbohydrates)

The overall products of photosynthesis are:

Glucose (carbohydrates)
Sulfur (in photosynthetic sulfur bacteria)

Photosynthesis Examples

Photosynthesis in green plants or oxygenic bacteria.

In plants and oxygenic bacteria like cyanobacteria, photosynthesis takes place in the presence of green pigment, chlorophyll.
It takes place in the thylakoids of the chloroplasts, resulting in products like oxygen gas, glucose, and water molecules.
Most of the glucose units in plants are linked to form starch or fructose or even sucrose.

Photosynthesis in sulfur bacteria

In purple sulfur bacteria, photosynthesis takes place in the presence of hydrogen sulfur rather than water.
Some of these bacteria like green sulfur bacteria have chlorophyll whereas other purple sulfur bacteria have carotenoids as photosynthetic pigments.
The result of photosynthesis in these bacteria are carbohydrates (not necessarily glucose), sulfur gas, and water molecules.

Importance of photosynthesis

Photosynthesis is the primary source of energy in autotrophs where they make their food by utilizing carbon dioxide, sunlight, and photosynthetic pigments.
Photosynthesis is equally essential for heterotrophs, as they derive their energy from the autotrophs.
Photosynthesis in plants is necessary to maintain the oxygen levels in the atmosphere.
Besides, the products of photosynthesis contribute to the carbon cycle occurring in the oceans, land, plants, and animals.
Similarly, it also helps maintain a symbiotic relationship between plants, animals, and humans.
Sunlight or solar energy is the primary source of all other forms of energy on earth, which is utilized through the process of photosynthesis.

Artificial photosynthesis

Artificial photosynthesis is a chemical process that mimics the biological process of utilization of sunlight, water and carbon dioxide to produce oxygen and carbohydrates.

Image Source: Phys .

In artificial photosynthesis, photocatalysts are utilized that are capable of replicating the oxidation-reduction reactions taking place during natural photosynthesis.
The main function of artificial photosynthesis is to produce solar fuel from sunlight that can be stored and used under conditions, where sunlight is not available.
As solar fuels are prepared, artificial photosynthesis can be used to produce just oxygen from water and sunlight, resulting in clean energy production.
The most important part of artificial photosynthesis is the photocatalytic splitting of a water molecule, resulting in oxygen and large quantities of hydrogen gas.
Further, light-driven carbon reduction can also be performed to replicate the process of natural carbon fixation, resulting in carbohydrates molecules.
Thus, artificial photosynthesis has applications in the production of solar fuels, photoelectrochemistry, engineering of enzymes, and photoautotrophic microorganisms for the production of microbial biofuel and biohydrogen from sunlight.

Video Animation: Learning from leaves: Going green with artificial photosynthesis

Photosynthesis vs. Cellular respiration

Image Source: Khan Academy .


Photosynthesis takes place in green plants, algae, and some photosynthetic bacteria.	takes place in all living organisms.
The process of photosynthesis occurs in the thylakoids of chloroplasts.	The process of cellular respiration occurs in mitochondria.
The reactants of photosynthesis are light energy, carbon dioxide, and water. 6CO + 6H O → C H O + 6O	The reactants of cellular respiration are glucose and oxygen. 6O + C H O → 6CO + 6H O
The products of photosynthesis are glucose and oxygen.	The products of cellular respiration are carbon dioxide and water.
Photosynthesis is an anabolic process, resulting in the production of organic molecules.	Cellular respiration is a catabolic process, resulting in the oxidation of organic molecules to release energy.
Photosynthesis is an endergonic reaction that results in the utilization of energy.	Cellular respiration is an exergonic reaction that results in the release of energy
Photosynthesis can only take place in the presence of sunlight.	Cellular respiration occurs all the time as it doesn’t require sunlight.

Video Animation: Photosynthesis vs. Cellular Respiration Comparison (BOGObiology)

FAQs (Revision Questions)

Where does photosynthesis occur? Photosynthesis occurs in the thylakoid membrane of the chloroplasts.

What are the products of photosynthesis? The products of photosynthesis are carbohydrates (glucose), oxygen, and water molecules.

What are the reactants of photosynthesis? The reactants of photosynthesis are carbon dioxide, water, photosynthetic pigments, and sunlight.

How are photosynthesis and cellular respiration related? Photosynthesis and cellular respiration are essentially the reverses of one another where photosynthesis is an anabolic process resulting in the formation of organic molecules. In contrast, cellular respiration is a catabolic process resulting in the breaking down of organic molecules to release energy.

Berg JM, Tymoczko JL, Stryer L. Biochemistry. 5th edition. New York: W H Freeman; 2002. Section 17.2, Entry to the Citric Acid Cycle and Metabolism Through It Are Controlled.Available from: https://www.ncbi.nlm.nih.gov/books/NBK22347/
Nelson DL and Cox MM. Lehninger Principles of Biochemistry. Fourth Edition.
Montero F. (2011) Photosynthetic Pigments. In: Gargaud M. et al. (eds) Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg
Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000. Section 16.3, Photosynthetic Stages and Light-Absorbing Pigments.Available from: https://www.ncbi.nlm.nih.gov/books/NBK21598/

About Author

Anupama Sapkota

1 thought on “Photosynthesis: Equation, Steps, Process, Diagram”

How can we say that 6 calvin cycles are needed to produce 1 glucose molecule why not 2?

photosynthesis summary

Learn how photosynthesis works and why it’s important.

photosynthesis , Process by which green plants and certain other organisms transform light into chemical energy. In green plants, light energy is captured by chlorophyll in the chloroplasts of the leaves and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds (simple and complex sugars) that are the basis of both plant and animal life. Photosynthesis is crucial for maintaining life on Earth; if it ceased, there would soon be little food or other organic matter on the planet, and most types of organisms would disappear.

Photosynthesis consists of a number of photochemical and enzymatic reactions. It occurs in two stages. During the light-dependent stage (“light” reactions), chlorophyll absorbs light energy, which excites some electrons in the pigment molecules to higher energy levels; these leave the chlorophyll and pass along a series of molecules, generating formation of NADPH (an enzyme) and high-energy ATP molecules. Oxygen , released as a by-product, passes into the atmosphere through pores in the leaves. NADPH and ATP drive the second stage, the “dark” reactions (or Calvin cycle, discovered by Melvin Calvin ), which do not require light. During this stage glucose is generated using atmospheric carbon dioxide.

Understanding Step by Step Process of Photosynthesis in Plants

Photosynthesis is the process through which plants convert light energy from the sun to chemical energy. The chemical energy is then stored as sugar. During the process of photosynthesis, plants capture light energy and use it to convert water, carbon dioxide, and minerals into oxygen (released into the air) and glucose (stored in the plant and used as food).

The photosynthesis process occurs in all plants and algae, as well as in some bacteria species. In addition to light energy, the process also requires water and carbon dioxide. And the end product is sugar.

Photosynthesis takes place inside plant cells in small things called as chloroplasts using chlorophyll – the green pigment in plants. While it usually occurs in leaves, it can also take place in stems albeit in minute proportion.

According to Britannica ,

“ Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds. “

Despite the fact that photosynthesis occurs in plants and algae, it is beneficial for all lifeforms on the Earth including humans.

In this article, we will have a detailed look at the process of photosynthesis and also explore its importance . Let’s get to it.

Step by Step Process of Photosynthesis

In light of the fact that photosynthesis occurs largely in plant leaves, you should understand the structure of the leaf before you learn how the process works.

A typical leaf is made up of the following parts:

Upper and lower epidermis
Spongy mesophyll
Palisade mesophyll
Vascular bundles

Photosynthesis does not occur in the upper and lower epidermis as they don’t have chloroplasts. These parts only serve as a protection of the inner cells of a leaf. The Stomata refer to the microscopic holes found mainly on the lower epidermis. They are for reverse respiration – allow carbon dioxide in and let oxygen out.

The vascular bundles are part of the plant’s transport system. They help in the movement of nutrients and water around the plant. Photosynthesis occurs in the palisade mesophyll cells as they have chloroplasts.

Now that we have that out of the way, let’s look at the 4 main steps of photosynthesis:

The plant takes in carbon dioxide in the atmosphere through the stomata on its leaves. It is worth noting that there are some stomata on the stems as well.

Water gets into the plant mainly through the roots and finds its way to the leaves, where photosynthesis occurs. Plant roots are specially designed to draw water from the ground and transport it to the plant leaves through the stem.

Chlorophyll, the green coloring matter of the leaf, traps the energy from sunlight as it shines on the leaf. It is worth noting that it is chlorophyll that gives the leaf its green color.

The solar energy is used to break water down into hydrogen and oxygen. Then hydrogen is combined with carbon dioxide to make sugar, which is food for the plant. Oxygen is released as a byproduct through the stomata.

Chemical reactions occur with the help of protons from the water molecules and electrons from the chlorophyll molecules to produce Adenosine Triphosphate (ATP). ATP provides energy for cellular reactions and Nicotinamide Adenine Dinucleotide Diphosphate (NADP), which is integral in plant metabolism.

Chemical Formula for the Process of Photosynthesis

This chemical formula summarizes the whole process of photosynthesis:

6CO2 +12H2O + Light → C6H12O6 + 6O2+ 6H2O

And there are six factors that influence the rate of photosynthesis:

Temperature
Light intensity
Light wavelength
Carbon dioxide availability
Chlorophyll concentration
Water availability

Namely, the higher the light intensity, temperature, carbon dioxide and chlorophyll concentration, the faster the rate at which photosynthesis occurs. But there is an optimum rate.

In the case of light intensity, photosynthesis rate is higher in red or blue light and very low in green light. Photosynthesis rate decreases with a decrease in water availability .

Now that you understand the process of photosynthesis let’s look at its importance.

Importance of Photosynthesis

Plants play an integral role in the continuity of life on the planet, all thanks to photosynthesis. They achieve that through the following:

1. Atmospheric Gases

In photosynthesis, plants take in carbon dioxide and release oxygen as a by-product. Without the process of photosynthesis, it would be difficult to replenish all the oxygen being used in processes such as combustion and respiration.

Moreover, the amount of carbon dioxide in the atmosphere would rise to dangerous levels. Therefore, it suffices to say that photosynthesis helps to balance atmospheric gases.

2. Food and Energy

Green plants produce their own food through photosynthesis. They are called producers. Conversely, animals and humans are consumers.

They get all of their food from plants, either directly or indirectly. In fact, the larger part of the world’s population gets over 80% of its food directly from plants. The remaining source is obtained from animals.

And animals are part of the food chain, which normally starts with plants. Speaking of the food chain , the energy you get from the food you eat is also a product of photosynthesis, whether the food is from plants or animals .

3. Petroleum Products

Did you know that your car runs on what was once light energy? Or that your cooking gas is a product of photosynthesis?

We get petroleum from plants that stored light energy in their system millions of years ago, thanks to photosynthesis, as well as animals that ate those plants.

The petroleum came into being due to intense pressure applied to the plants and animals over millions of years. Coal and natural gas were also produced in the same way.

4. Wood and Other Side Products

We use wood for a wide range of purposes, including construction and combustion. Paper is also a product of wood.

Moreover, cotton and other natural fibers consist of cellulose produced virtually entirely by photosynthesizing plants. And while wood comes from the sheep, the sheep gets its food from the plants. It is, therefore, suffice to say that we wear clothes courtesy of photosynthesis.

5. Medicinal Products

Most medicines are manufactured using various chemicals extracted from plants. And thousands of plants have been confirmed to have medicinal properties. Aspirin, for example, is derived from salicylic acid.

Salicylic acid comes from the back of the willow tree. Aspirin is a popular painkiller. It is also used to minimize blood clotting in heart patients.

Much stronger analgesic drugs such as codeine and morphine are products of opium. Opium is extracted from the seeds of the poppy plant.

Tests are still ongoing to ascertain the medicinal status of thousands of other plants species, especially those found in the tropical rainforests . In the light of this, it is imperative that we protect the natural habitats of these plant species.

Bottom Line

Photosynthesis is the process used by plants, algae, and some bacteria to convert solar energy into chemical energy. Besides light energy, other photosynthesis ingredients are water and carbon dioxide. It is a complex, enzyme-controlled process that is vital for the existence of all lifeforms on Planet Earth . Namely, all living things are dependent on plants, directly or indirectly.

Photo by: Khanh , pexels

I am Sonia Madaan, a mother with a passion for science, computing, and environmental issues. Motivated by my passion and education, I started a website to spread awareness about climate change and its causes, like rising greenhouse gas levels. You can read more about me here .

Types, Importance and Examples of Food Chain

A food chain is a sequence of transfer of matter and energy through food, from one organism to another. Due to the fact that most consumers in a food chain feed on more than one type of plant or animal, an intertwined network of the food chain is often found in most ecosystems. This complex…

Why are Forests Important and Why We Need Them?

Forests are our land’s trees and plants that cover a third of the earth’s surface symbolized by the color green in the common definition of environmentalism. There are many reasons why forests are an important feature for the environment and in our daily lives.They are fundamental life forms and provide for the continuity of the…

What is Greenhouse Effect and What are Greenhouse Gases?

A greenhouse is a house made up of glass. It can be used to grow flowers and plants as it has glass walls and a glass roof. When sun shines, it warms the plants and air inside. The heat that is grabbed inside the greenhouse can’t escape out and therefore it remains warmer which is…

Can Plants Photosynthesize With Artificial light?

Nowadays, it’s common to find house plants in nearly every room in the house. They’re used to beautify the spaces in our homes. Plants are photosynthetic organisms. This means that they require light to produce energy for themselves. The significance of photosynthesis in the maintenance of life on earth can’t be overstated. There would be…

Phosphorus Cycle: Definition, Steps and Interesting Facts

Phosphorous is a crucial nutrient for plants and animals. For instance, it forms an integral component of genes and also plays a significant role in the Adenosine Triphosphate (ATP) energy cycle. Without phosphorous, you wouldn’t be able to contract your muscles. The phosphorus cycle refers to the biogeochemical cycle by which phosphorous moves through the…

13+ Brilliant Facts About Ozone Layer That Will Blow Your Mind

The Ozone Layer is an important element in the history of life on earth. Without it, many living things probably would not exist and the earth would be extremely different. Millions of years ago, only single cell creatures existed on earth. At that time, the earth had no oxygen that would support life. But as…

5.1 Overview of Photosynthesis

Learning objectives.

Summarize the process of photosynthesis
Explain the relevance of photosynthesis to other living things
Identify the reactants and products of photosynthesis
Describe the main structures involved in photosynthesis

All living organisms on earth consist of one or more cells. Each cell runs on the chemical energy found mainly in carbohydrate molecules (food), and the majority of these molecules are produced by one process: photosynthesis. Through photosynthesis, certain organisms convert solar energy (sunlight) into chemical energy, which is then used to build carbohydrate molecules. The energy used to hold these molecules together is released when an organism breaks down food. Cells then use this energy to perform work, such as cellular respiration.

The energy that is harnessed from photosynthesis enters the ecosystems of our planet continuously and is transferred from one organism to another. Therefore, directly or indirectly, the process of photosynthesis provides most of the energy required by living things on earth.

Photosynthesis also results in the release of oxygen into the atmosphere. In short, to eat and breathe, humans depend almost entirely on the organisms that carry out photosynthesis.

Link to Learning

Click the following link to learn more about photosynthesis.

Solar Dependence and Food Production

Some organisms can carry out photosynthesis, whereas others cannot. An autotroph is an organism that can produce its own food. The Greek roots of the word autotroph mean “self” ( auto ) “feeder” ( troph ). Plants are the best-known autotrophs, but others exist, including certain types of bacteria and algae ( Figure 5.2 ). Oceanic algae contribute enormous quantities of food and oxygen to global food chains. Plants are also photoautotrophs , a type of autotroph that uses sunlight and carbon from carbon dioxide to synthesize chemical energy in the form of carbohydrates. All organisms carrying out photosynthesis require sunlight.

Heterotrophs are organisms incapable of photosynthesis that must therefore obtain energy and carbon from food by consuming other organisms. The Greek roots of the word heterotroph mean “other” ( hetero ) “feeder” ( troph ), meaning that their food comes from other organisms. Even if the food organism is another animal, this food traces its origins back to autotrophs and the process of photosynthesis. Humans are heterotrophs, as are all animals. Heterotrophs depend on autotrophs, either directly or indirectly. Deer and wolves are heterotrophs. A deer obtains energy by eating plants. A wolf eating a deer obtains energy that originally came from the plants eaten by that deer. The energy in the plant came from photosynthesis, and therefore it is the only autotroph in this example ( Figure 5.3 ). Using this reasoning, all food eaten by humans also links back to autotrophs that carry out photosynthesis.

Everyday Connection

Photosynthesis at the grocery store.

Major grocery stores in the United States are organized into departments, such as dairy, meats, produce, bread, cereals, and so forth. Each aisle contains hundreds, if not thousands, of different products for customers to buy and consume ( Figure 5.4 ).

Although there is a large variety, each item links back to photosynthesis. Meats and dairy products link to photosynthesis because the animals were fed plant-based foods. The breads, cereals, and pastas come largely from grains, which are the seeds of photosynthetic plants. What about desserts and drinks? All of these products contain sugar—the basic carbohydrate molecule produced directly from photosynthesis. The photosynthesis connection applies to every meal and every food a person consumes.

Main Structures and Summary of Photosynthesis

Photosynthesis requires sunlight, carbon dioxide, and water as starting reactants ( Figure 5.5 ). After the process is complete, photosynthesis releases oxygen and produces carbohydrate molecules, most commonly glucose. These sugar molecules contain the energy that living things need to survive.

The complex reactions of photosynthesis can be summarized by the chemical equation shown in Figure 5.6 .

Although the equation looks simple, the many steps that take place during photosynthesis are actually quite complex, as in the way that the reaction summarizing cellular respiration represented many individual reactions. Before learning the details of how photoautotrophs turn sunlight into food, it is important to become familiar with the physical structures involved.

In plants, photosynthesis takes place primarily in leaves, which consist of many layers of cells and have differentiated top and bottom sides. The process of photosynthesis occurs not on the surface layers of the leaf, but rather in a middle layer called the mesophyll ( Figure 5.7 ). The gas exchange of carbon dioxide and oxygen occurs through small, regulated openings called stomata .

In all autotrophic eukaryotes, photosynthesis takes place inside an organelle called a chloroplast . In plants, chloroplast-containing cells exist in the mesophyll. Chloroplasts have a double (inner and outer) membrane. Within the chloroplast is a third membrane that forms stacked, disc-shaped structures called thylakoids . Embedded in the thylakoid membrane are molecules of chlorophyll , a pigment (a molecule that absorbs light) through which the entire process of photosynthesis begins. Chlorophyll is responsible for the green color of plants. The thylakoid membrane encloses an internal space called the thylakoid space. Other types of pigments are also involved in photosynthesis, but chlorophyll is by far the most important. As shown in Figure 5.7 , a stack of thylakoids is called a granum , and the space surrounding the granum is called stroma (not to be confused with stomata, the openings on the leaves).

Visual Connection

On a hot, dry day, plants close their stomata to conserve water. What impact will this have on photosynthesis?

The Two Parts of Photosynthesis

Photosynthesis takes place in two stages: the light-dependent reactions and the Calvin cycle. In the light-dependent reactions , which take place at the thylakoid membrane, chlorophyll absorbs energy from sunlight and then converts it into chemical energy with the use of water. The light-dependent reactions release oxygen from the hydrolysis of water as a byproduct. In the Calvin cycle, which takes place in the stroma, the chemical energy derived from the light-dependent reactions drives both the capture of carbon in carbon dioxide molecules and the subsequent assembly of sugar molecules. The two reactions use carrier molecules to transport the energy from one to the other. The carriers that move energy from the light-dependent reactions to the Calvin cycle reactions can be thought of as “full” because they bring energy. After the energy is released, the “empty” energy carriers return to the light-dependent reactions to obtain more energy. The two-stage, two-location photosynthesis process was discovered by Joan Mary Anderson, whose continuing work over the subsequent decades provided much of our understanding of the process, the membranes, and the chemicals involved.

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Access for free at https://openstax.org/books/concepts-biology/pages/1-introduction

Authors: Samantha Fowler, Rebecca Roush, James Wise
Publisher/website: OpenStax
Book title: Concepts of Biology
Publication date: Apr 25, 2013
Location: Houston, Texas
Book URL: https://openstax.org/books/concepts-biology/pages/1-introduction
Section URL: https://openstax.org/books/concepts-biology/pages/5-1-overview-of-photosynthesis

© Jul 10, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.

What is photosynthesis?

Photosynthesis is the process plants, algae and some bacteria use to turn sunlight, carbon dioxide and water into sugar and oxygen.

close up of an avocado leaf with a stem running diagonally from left to right

Photosynthetic processes
Photosynthesis equation
The carbon exchange
How do plants absorb sunlight?

How does photosynthesis start?

Location of photosynthesis

Light-dependent reactions

The Calvin cycle

Types of photosynthesis

Additional resources.

Photosynthesis is the process used by plants, algae and some bacteria to turn sunlight into energy. The process chemically converts carbon dioxide (CO2) and water into food (sugars) and oxygen . The chemical reaction often relies on a pigment called chlorophyll, which gives plants their green color. Photosynthesis is also the reason our planet is blanketed in an oxygen-rich atmosphere.

Types of photosynthetic processes

There are two types of photosynthesis: oxygenic and anoxygenic. They both follow very similar principles, but the former is the most common and is seen in plants, algae and cyanobacteria.

During oxygenic photosynthesis, light energy transfers electrons from water (H2O) taken up by plant roots to CO2 to produce carbohydrates . In this transfer, the CO2 is "reduced," or receives electrons, and the water is "oxidized," or loses electrons. Oxygen is produced along with carbohydrates.

This process creates a balance on Earth, in which the carbon dioxide produced by breathing organisms as they consume oxygen in respiration is converted back into oxygen by plants, algae and bacteria.

Anoxygenic photosynthesis, meanwhile, uses electron donors that are not water and the process does not generate oxygen, according to "Anoxygenic Photosynthetic Bacteria" by LibreTexts . The process typically occurs in bacteria such as green sulfur bacteria and phototrophic purple bacteria.

The Photosynthesis equation

Though both types of photosynthesis are complex, multistep affairs, the overall process can be neatly summarized as a chemical equation.

The oxygenic photosynthesis equation is:

6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O

Here, six molecules of carbon dioxide (CO2) combine with 12 molecules of water (H2O) using light energy. The end result is the formation of a single carbohydrate molecule (C6H12O6, or glucose) along with six molecules each of oxygen and water.

Similarly, the various anoxygenic photosynthesis reactions can be represented as a single generalized formula:

CO2 + 2H2A + Light Energy → [CH2O] + 2A + H2O

The letter A in the equation is a variable, and H2A represents the potential electron donor. For example, "A" may represent sulfur in the electron donor hydrogen sulfide (H2S), according to medical and life sciences news site News Medical Life Sciences .

How is carbon dioxide and oxygen exchanged?

stomata are the gatekeepers of the leaf, allowing gas exchange between the leaf and surrounding air.

Plants absorb CO2 from the surrounding air and release water and oxygen via microscopic pores on their leaves called stomata.

When stomata open, they let in CO2; however, while open, the stomata release oxygen and let water vapor escape. Stomata close to prevent water loss, but that means the plant can no longer gain CO2 for photosynthesis. This tradeoff between CO2 gain and water loss is a particular problem for plants growing in hot, dry environments.

How do plants absorb sunlight for photosynthesis?

Plants contain special pigments that absorb the light energy needed for photosynthesis.

Chlorophyll is the primary pigment used for photosynthesis and gives plants their green color, according to science education site Nature Education . Chlorophyll absorbs red and blue light and reflects green light. Chlorophyll is a large molecule and takes a lot of resources to make; as such, it breaks down towards the end of the leaf's life, and most of the pigment's nitrogen (one of the building blocks of chlorophyll) is resorbed back into the plant, When leaves lose their chlorophyll in the fall, other leaf pigments such as carotenoids and anthocyanins begin to show. While carotenoids primarily absorb blue light and reflect yellow, anthocyanins absorb blue-green light and reflect red light, according to Harvard University's The Harvard Forest .

Related: What if humans had photosynthetic skin?

Pigment molecules are associated with proteins, which allow them the flexibility to move toward light and toward one another. A large collection of 100 to 5,000 pigment molecules constitutes an "antenna," according to an article by Wim Vermaas , a professor at Arizona State University. These structures effectively capture light energy from the sun, in the form of photons.

The situation is a little different for bacteria. While cyanobacteria contain chlorophyll, other bacteria, for example, purple bacteria and green sulfur bacteria, contain bacteriochlorophyll to absorb light for anoxygenic photosynthesis, according to " Microbiology for Dummies " (For Dummies, 2019).

It was previously hypothesized that just a small number of photons would be needed to kickstart photosynthesis, but researchers never successfully observed this first step. However, in 2023, scientists discovered that photosynthesis appears to begin with a single photon.

The researchers set up an experiment where a photon source spat out two photons at a time. One was absorbed by a detector, while the other hit a bacteria's chloroplast equivalent. When the second photon hit, photosynthesis began.

After performing the test over 1.5 million times, the researchers confirmed that just one photon is needed to start photosynthesis.

Where in the plant does photosynthesis take place?

Plants need energy from sunlight for photosynthesis to occur.

Photosynthesis occurs in chloroplasts, a type of plastid (an organelle with a membrane) that contains chlorophyll and is primarily found in plant leaves.

Chloroplasts are similar to mitochondria , the energy powerhouses of cells, in that they have their own genome, or collection of genes, contained within circular DNA. These genes encode proteins that are essential to the organelle and to photosynthesis.

Inside chloroplasts are plate-shaped structures called thylakoids that are responsible for harvesting photons of light for photosynthesis, according to the biology terminology website Biology Online . The thylakoids are stacked on top of each other in columns known as grana. In between the grana is the stroma — a fluid containing enzymes, molecules and ions, where sugar formation takes place.

Ultimately, light energy must be transferred to a pigment-protein complex that can convert it to chemical energy, in the form of electrons. In plants, light energy is transferred to chlorophyll pigments. The conversion to chemical energy is accomplished when a chlorophyll pigment expels an electron, which can then move on to an appropriate recipient.

The pigments and proteins that convert light energy to chemical energy and begin the process of electron transfer are known as reaction centers.

When a photon of light hits the reaction center, a pigment molecule such as chlorophyll releases an electron.

The released electron escapes through a series of protein complexes linked together, known as an electron transport chain. As it moves through the chain, it generates the energy to produce ATP (adenosine triphosphate, a source of chemical energy for cells) and NADPH — both of which are required in the next stage of photosynthesis in the Calvin cycle. The "electron hole" in the original chlorophyll pigment is filled by taking an electron from water. This splitting of water molecules releases oxygen into the atmosphere.

Light-independent reactions: The Calvin cycle

Photosynthesis involves a process called the Calvin cycle to use energy stored from the light-dependent reactions to fix CO2 into sugars needed for plant growth.

The Calvin cycle is the three-step process that generates sugars for the plant, and is named after Melvin Calvin , the Nobel Prize -winning scientist who discovered it decades ago. The Calvin cycle uses the ATP and NADPH produced in chlorophyll to generate carbohydrates. It takes plate in the plant stroma, the inner space in chloroplasts.

In the first step of this cycle, called carbon fixation, an enzyme called RuBP carboxylase/oxygenase, also known as rubiso, helps incorporate CO2 into an organic molecule called 3-phosphoglyceric acid (3-PGA). In the process, it breaks off a phosphate group on six ATP molecules to convert them to ADP, releasing energy in the process, according to LibreTexts.

In the second step, 3-PGA is reduced, meaning it takes electrons from six NADPH molecules and produces two glyceraldehyde 3-phosphate (G3P) molecules.

One of these G3P molecules leaves the Calvin cycle to do other things in the plant. The remaining G3P molecules go into the third step, which is regenerating rubisco. In between these steps, the plant produces glucose, or sugar.

Three CO2 molecules are needed to produce six G3P molecules, and it takes six turns around the Calvin cycle to make one molecule of carbohydrate, according to educational website Khan Academy.

There are three main types of photosynthetic pathways: C3, C4 and CAM. They all produce sugars from CO2 using the Calvin cycle, but each pathway is slightly different.

The three main types of photosynthetic pathways are C3, C4 and CAM.

C3 photosynthesis

Most plants use C3 photosynthesis, according to the photosynthesis research project Realizing Increased Photosynthetic Efficiency (RIPE) . C3 plants include cereals (wheat and rice), cotton, potatoes and soybeans. This process is named for the three-carbon compound 3-PGA that it uses during the Calvin cycle.

C4 photosynthesis

Plants such as maize and sugarcane use C4 photosynthesis. This process uses a four-carbon compound intermediate (called oxaloacetate) which is converted to malate , according to Biology Online. Malate is then transported into the bundle sheath where it breaks down and releases CO2, which is then fixed by rubisco and made into sugars in the Calvin cycle (just like C3 photosynthesis). C4 plants are better adapted to hot, dry environments and can continue to fix carbon even when their stomata are closed (as they have a clever storage solution), according to Biology Online.

CAM photosynthesis

Crassulacean acid metabolism (CAM) is found in plants adapted to very hot and dry environments, such as cacti and pineapples, according to the Khan Academy. When stomata open to take in CO2, they risk losing water to the external environment. Because of this, plants in very arid and hot environments have adapted. One adaptation is CAM, whereby plants open stomata at night (when temperatures are lower and water loss is less of a risk). According to the Khan Academy, CO2 enters the plants via the stomata and is fixed into oxaloacetate and converted into malate or another organic acid (like in the C4 pathway). The CO2 is then available for light-dependent reactions in the daytime, and stomata close, reducing the risk of water loss.

Discover more facts about photosynthesis with the educational science website sciencing.com . Explore how leaf structure affects photosynthesis with The University of Arizona . Learn about the different ways photosynthesis can be measured with the educational science website Science & Plants for Schools .

This article was updated by Live Science managing editor Tia Ghose on Nov. 3, 2022.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Daisy Dobrijevic joined Space.com in February 2022 as a reference writer having previously worked for our sister publication All About Space magazine as a staff writer. Before joining us, Daisy completed an editorial internship with the BBC Sky at Night Magazine and worked at the National Space Centre in Leicester, U.K., where she enjoyed communicating space science to the public. In 2021, Daisy completed a PhD in plant physiology and also holds a Master's in Environmental Science, she is currently based in Nottingham, U.K.

Fossils from Greenland's icy heart reveal it was a green tundra covered in flowers less than 1 million years ago

3 remarkable trees: A living fossil, a deadly canopy, and the world's biggest seeds that were once mounted in gold by royals

Sexually frustrated dolphin behind spate of attacks on humans off Japan

A Step-by-step Guide to Understand the Process of Photosynthesis

Photosynthesis helps plants to generate glucose, carbohydrates, and oxygen by using carbon dioxide, water, and sunlight. In this article, we attempt to answer all your queries about this process.

Like it? Share it!

The foremost thing that one needs to understand is that photosynthesis is important for all lifeforms on the Earth and not just plants. There is no questioning the fact that it occurs in plants, algae, and some species of bacteria, but indirectly, it helps all the organisms which cannot produce their own food, including humans.

Plants, algae, and species of bacteria that can produce their own food are known as photoautotrophs. These organisms―the plants in particular―resort to photosynthesis to convert carbon dioxide into organic compounds by using the energy derived from the Sun. The process is also known as carbon fixation process, as it produces carbon compounds which store chemical energy meant to be used in cell growth.

Photosynthesis Process Step by Step

By definition, photosynthesis is a process by which photoautotrophs convert the energy derived from the Sun into usable chemical energy. Light, water, chlorophyll, and carbon dioxide are the basic requirements for this process.

Carbon dioxide in the atmosphere enters the plant leaf through stomata, i.e., minute epidermal pores in the leaves and stem of plants which facilitate the transfer of various gases and water vapor.

Water enters the leaves, primarily through the roots. These roots are especially designed to draw the ground water and transport it to the leaves through the stem.

As sunlight falls on the leaf surface, the chlorophyll, i.e., the green pigment present in the plant leaf, traps the energy in it. Interestingly, the green color of the leaf is also attributed to presence of chlorophyll.

Then hydrogen and oxygen are produced by converting water using the energy derived from the Sun. Hydrogen is combined with carbon dioxide in order to make food for the plant, while oxygen is released through the stomata. Similarly, even algae and bacteria use carbon dioxide and hydrogen to prepare food, while oxygen is let out as a waste product.

The electrons from the chlorophyll molecules and protons from the water molecules facilitate chemical reactions in the cell. These reactions produce ATP (adenosine triphosphate), which provides energy for cellular reactions, and NADP (nicotinamide adenine dinucleotide diphosphate), essential in plant metabolism.

The entire process can be explained by a single chemical formula.

6CO 2 +12H 2 O + Light → C 6 H 12 O 6 + 6O 2 + 6H 2 O

While we take in oxygen and give out carbon dioxide to produce energy, plants take in carbon dioxide and give out oxygen to produce energy.

Photosynthesis has several benefits, not just for the photoautotrophs, but also for humans and animals. The chemical energy stored in plants is transferred to animals and humans when they consume plant matter. It also helps in maintaining a normal level of oxygen and carbon dioxide in the atmosphere. Almost all the oxygen present in the atmosphere can be attributed to this process, which also means that respiration and photosynthesis go together.

Get Updates Right to Your Inbox

Privacy overview.

INFOGRAPHIC

Photosynthesis.

Learn about the process that plants, algae, and some bacteria use to make their own food and the oxygen we breathe.

Biology, Ecology

Loading ...

Media credits.

Production Managers

Program specialists, specialist, content production, last updated.

October 19, 2023

User Permissions

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

IMAGES

Diagram showing process of photosynthesis in plant 1858779 Vector Art
[Class 7] Photosynthesis
Photosynthesis
A Step-by-step Guide to Understand the Process of Photosynthesis
Diagram showing process of photosynthesis with plant and cells 7092845
Short note on Photosynthesis

VIDEO

how photosynthesis takes place in plants & Process Of Photosynthesis (animated)
Photosynthesis (UPDATED)
Photosynthesis 🌷
Photosynthesis
Photosynthesis
What is Photosynthesis?

COMMENTS

Photosynthesis
Photosynthesis | Definition, Formula, Process, Diagram, ...
Photosynthesis
Learn how plants use sunlight, water, and carbon dioxide to produce oxygen and sugar through photosynthesis. Explore the stages, types, and benefits of this process that supports most life on Earth.
Photosynthesis
Learn how photosynthetic organisms convert light energy into chemical energy and produce oxygen or sulfur. Explore the differences and similarities between oxygenic and anoxygenic photosynthesis, and the role of photosynthesis in climate and life.
Photosynthesis
Learn how plants and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen in photosynthesis. Explore the factors, equation, structure, and importance of photosynthesis with examples and diagrams.
Explainer: How photosynthesis works
Learn how plants and algae use light, water and carbon dioxide to make sugar and oxygen through photosynthesis. Discover the two processes of photosynthesis: the light reaction and the Calvin cycle, and how they happen in chloroplasts.
Photosynthesis
Learn how plants use light energy to convert carbon dioxide and water into glucose and oxygen in two steps: the light reactions and the Calvin cycle. Find out the chemical equation, the products, and the quiz questions of photosynthesis.
Photosynthesis
Learn how plants, algae, and certain bacteria use light energy from the sun to make glucose and oxygen in photosynthesis. Find out the stages, factors, and importance of this process, and see the diagram and equation.
Photosynthesis, Chloroplast
Learn how photosynthesis converts light energy into organic molecules and oxygen, and how different organisms use it. Explore the structure and function of chloroplasts, the organelles that contain chlorophyll and other pigments.
Photosynthesis: Equation, Steps, Process, Diagram
Learn about photosynthesis, the process of converting light energy into chemical energy by plants and bacteria. Find out the equations, steps, diagrams, pigments, factors, products, and examples of photosynthesis.
How photosynthesis and its light and dark reactions work
Learn how photosynthesis works and why it's important for life on Earth. See diagrams and explanations of the light and dark reactions, and the role of chlorophyll, water, carbon dioxide, and oxygen.
Khan Academy
Intro to photosynthesis (article)
Understanding Step by Step Process of Photosynthesis in Plants
Learn how plants convert light energy into chemical energy using chlorophyll and water. Discover the chemical formula, the factors that influence the rate, and the benefits of photosynthesis for life on Earth.
5.1 Overview of Photosynthesis
After the process is complete, photosynthesis releases oxygen and produces carbohydrate molecules, most commonly glucose. These sugar molecules contain the energy that living things need to survive. Figure 5.5 Photosynthesis uses solar energy, carbon dioxide, and water to release oxygen and to produce energy-storing sugar molecules.
What is photosynthesis?
Photosynthesis is the process used by plants, algae and some bacteria to turn sunlight into energy. The process chemically converts carbon dioxide (CO2) and water into food (sugars) and oxygen .
A Step-by-step Guide to Understand the Process of Photosynthesis
Learn how plants, algae, and some bacteria use photosynthesis to convert carbon dioxide, water, and sunlight into glucose, carbohydrates, and oxygen. Find out the chemical formula, the role of chlorophyll, and the importance of this process for all lifeforms on Earth.
Photosynthesis
Photosynthesis. Learn about the process that plants, algae, and some bacteria use to make their own food and the oxygen we breathe.
Khan Academy
Learn how plants use sunlight to produce sugar and oxygen in the process of photosynthesis. Explore the biology library for more topics.

ENCYCLOPEDIC ENTRY

Loading ...

Media Credits

Production Managers

User Permissions

Interactives

Related Resources

Photosynthesis

What Is Photosynthesis in Biology?

Where Does This Process Occur?

Photosynthesis Equation

Structure Of Chlorophyll

Process Of Photosynthesis

Light Reaction of Photosynthesis (or) Light-dependent Reaction

Dark Reaction of Photosynthesis (or) Light-independent Reaction

Importance of Photosynthesis

Frequently Asked Questions

Leave a Comment Cancel reply

Register with BYJU'S & Download Free PDFs

It’s a wonderful world — and universe — out there.

Science News Explores

Share this:

Let the light shine in

Give me some sugar

The Calvin cycle has four major steps:

More Stories from Science News Explores on Plants

Many flowers and ferns lure in ants as bodyguards

This squid-like ‘fairy lantern’ plant is new to science

Microbes in the Arctic may be releasing more climate-warming gases

Gene editing may help rice better withstand climate change

Flowers may electrically detect bees buzzing nearby

Let’s learn about photosynthesis

Experiment: Can plants stop soil erosion?

On hot summer days, this thistle stays cool to the touch

Photosynthesis

Photosynthesis Definition

Photosynthesis Equation

Stages of Photosynthesis

The Calvin Cycle

Products of Photosynthesis

Cite This Article

Photosynthesis

Where does Photosynthesis Occur

What Happens During Photosynthesis

Stages of the Process

Factors Affecting the Rate of Photosynthesis

Importance of Photosynthesis

Related articles

Leave a Reply Cancel reply

Popular Articles

Join our Newsletter

Related Worksheets

Photosynthetic Cells

What Is Photosynthesis? Why Is it Important?

What Cells and Organelles Are Involved in Photosynthesis?

What Are the Steps of Photosynthesis?

Topic rooms within Cell Biology

Visual Browse

Photosynthesis: Equation, Steps, Process, Diagram

Photosynthesis equations/reactions/formula

Video Animation: Photosynthesis (Crash Course)

Photosynthetic pigments

Chlorophyll

Bacteriorhodopsin

Phycobilins

Carotenoids

Factors affecting photosynthesis

Carbon dioxide

Temperature

Process/ Steps of Photosynthesis

1. Absorption of light

2. Electron Transfer

3. Generation of ATP

4. Carbon Fixation

Types/ Stages/ Parts of photosynthesis

1. Light-dependent reactions

Photosystem II

Photosystem I

Video Animation: The Light Reactions of Photosynthesis (Ricochet Science)

2. Light independent reactions (Calvin cycle)