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Explain the miller's experiment with the help of diagrams?

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• Introduction

Original protocol and results

Additional trials and discoveries, significance.

Miller-Urey experiment

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• Nature - The role of borosilicate glass in Miller–Urey experiment
• Frontiers - Frontiers in Physics - The spark of life: discharge physics as a key aspect of the Miller–Urey experiment
• National Center for Biotechnology Information - PubMed Central - Conducting Miller-Urey Experiments
• National Center for Science Education - The Miller-Urey Experiment
• Table Of Contents

Miller-Urey experiment , experimental simulation conducted in 1953 that attempted to replicate the conditions of Earth ’s early atmosphere and oceans to test whether organic molecules could be created abiogenically, that is, formed from chemical reactions occurring between inorganic molecules thought to be present at the time. The experiment—the results of which were published in the journal Science as “A Production of Amino Acids Under Possible Primitive Earth Conditions”—documented the production of amino acids and other organic molecules, thereby demonstrating that chemical evolution (that is, the formation of complex chemicals from simple ones) is possible. The Miller-Urey experiment is used as evidence to support hypotheses about the origins of life .

The Miller-Urey experiment was conducted by American chemist Stanley Miller under the supervision of American scientist Harold C. Urey at the University of Chicago . The experiment was designed to test ideas introduced independently in the 1920s by Russian biochemist Aleksandr Oparin and British physiologist J.B.S. Haldane , both of whom suggested that organic molecules, such as amino acids and sugars , could be formed from abiogenic materials when acted on by an external energy source within the context of a reducing atmosphere, that is, one with low levels of free oxygen ( see also oxidation-reduction reaction ). At the time, it was thought that the atmosphere of early Earth between 4 billion and 3.5 billion years ago was primarily composed of ammonia and water vapour. Oparin and Haldane noted that from this “primordial soup” of materials the first organic molecules arose, which became the precursors to molecules of ever-increasing complexity that resulted in the development of living cells ( see also abiogenesis ).

To test Oparin and Haldane’s ideas, Miller and Urey designed a closed experiment in a laboratory . They constructed an enclosed glass apparatus with two large boiling flasks connected to each other with glass tubing, in which water could pool, gases could mix, and matter could change phases between liquid and gas. A large lower chamber was filled with water (a boiling flask that stood in for the oceans), and the water was boiled to produce water vapour, which ascended into the large upper chamber (a boiling flask that simulated Earth’s early atmosphere). Additional tubing allowed material to descend from the upper chamber through a condenser, where water vapour would condense into liquid and fall into a collection trap from which samples could be taken. This trap was set slightly below the lower chamber, but it was also connected to the lower chamber above the water line. The researchers removed the air from the apparatus, replacing it throughout with ammonia, hydrogen , and methane gases, and they let the various materials cycle through liquid and gas phases.

In an early run of the experiment, Miller discovered that the energy produced from boiling water was not enough to drive the chemical reactions necessary to approximate the conditions of early Earth, so in a second version of the experiment (the one whose results were published in 1953) he added electrodes to the upper chamber. After the water was boiled, the mix of gases circulated through the system past electrodes that discharged sparks (which simulated lightning ), and a condenser converted some of the gas to liquid so that it could return to the lower chamber. This process ran continuously for one week. After this period, the contents of the apparatus had visibly changed colour. A red- and yellow-coloured solution had started to collect in the trap after running the experiment for a few days and became a broth of red and brown by the experiment’s end.

To determine the identity of the molecules that resulted from their procedure, Miller and Urey terminated the reaction, added chemicals that prevented the growth of microbes (which could be introduced to the closed system when samples were collected from the broth), extracted samples of the solution, and analyzed them using paper chromatography . They discovered several types of simple organic molecules in the samples, including amino acids, some of which were relevant as the building blocks of the proteins that are present in all living organisms. Miller was able to identify the amino acids glycine , alpha-alanine (α-alanine), and beta-alanine (β-alanine) confidently; however, he was less certain about the presence of aspartic acid and α-amino- n -butyric acid, whose signs in the analysis were weak.

Miller modified the original experiment several times, and each modification captured possible variations in Earth conditions that might influence the system’s products. Some of Miller’s subsequent experiments used different energy sources, such as an electrical source that produced a silent discharge instead of a spark, and improved gas circulation through the addition of glass tubing. Other researchers also repeated the experiment during the 1950s using different energy sources, such as ultraviolet light , and used different atmospheric gases (such as carbon dioxide , hydrogen sulfide , and nitrogen ) in various combinations, which also resulted in a mix of organic chemicals but only a handful of amino acids.

Miller and others would repeat the experiment several times in subsequent decades. He reran the experiment in the early 1970s using better analytical equipment, which revealed the presence of 33 different amino acids, including more than half of the 20 or so that appear in proteins present in living things. Researchers later criticized Miller for using what they considered to be the wrong gases in the experiment; carbon dioxide and nitrogen, not ammonia and methane, were shown later to be the primary gases in Earth’s early atmosphere, with ammonia and methane occurring only in minor amounts. Miller’s 1983 trial replaced methane and ammonia with carbon dioxide and nitrogen; however, fewer amino acids were produced than in the original published experiment. This result was attributed later to a buildup of nitrites in the system, which made the mixture more acidic and caused the amino acids to break down before they could be identified.

American chemist Jeffrey Bada of the Scripps Institution of Oceanography reran the experiment in 2007. In addition to simulating an atmosphere filled with carbon dioxide and nitrogen, he added iron and carbonates to the system (two materials that would have been present in large amounts on ancient Earth)—which neutralized both the nitrites and the acids in the system, thereby allowing the amino acids to persist. A group of Spanish and Italian researchers suggested in 2021 that materials in the glass apparatus itself may have also catalyzed the chemical reactions taking place within it; the various chemicals in the experiment were shown to have reacted with the interior surface of the glass to release silicates (which, in turn, reacted with other chemicals) while also leaving behind small imperfections and cracks on the interior surface that may have served as chambers for other chemical reactions.

Starting in the early 2000s, researchers examined archived vials containing samples of material collected from Miller’s experiments during the 1950s. Aided by modern analytical equipment, they discovered far more than the five amino acids Miller reported in his papers; Miller’s experiments conducted in 1953 and 1958 were each shown to have yielded more than 20 amino acids.

The experiment showed that amino acids, which are important components of proteins (which are critical to life on Earth), could have arisen from inorganic compounds during Earth’s prebiotic phase. It also demonstrated that the speculation that life could have originated through chemical reactions among nonliving materials is possible and that this hypothesis could be tested scientifically. The Miller-Urey experiment sparked research on how simple organic molecules might polymerize into more complex molecules, a process that may have produced the first living cells. Scientists have also considered the possibility that meteors brought the first organic molecules, formed in space, to Earth, and they continue to modify the Miller-Urey protocol to test new ideas about chemical reactions in primitive Earth conditions.

What is Miller Urey experiment

Urey and miller experiment provides evidence for the origin of life from non living matter. the primitive atmosphere of earth was reducing and had high temperature, volcanic storms containing ch4, nh3, h2, etc. urey and miller created the same atmosphere and took the same compounds in a closed flask along with water vapour at 800ºc and created an electric discharge. they observed the formation of biomolecules such as amino acids, simple sugars, fats, etc. in the flask. they believed that these simple molecules formed complex molecules in the reducing environment of earth that were the precursors of life..

Urey and Miller Experiment Short Notes | Evolution Class 12 Notes

Urey and miller experiment short notes.

• Life originated from chemicals through a series of chemical reaction in ocean
• Origin of life by chemical evolution was proposed by oparin and haldane
• No experimental evidence for oparin views until 1953
• In 1953, Urey and his student miller gives evidence for this chemical evolution

EXPERIMENT OF MILLER & UREY

• Miller created primitive earth conditions in laboratory
• He took CH4,NH3,H2 and Water vapor in large flask
• He created eclectic shock by using two tungsten electrodes as source of energy
• The mixture cooled in condenser and liquefied and liquid was collected another flask
• After two weeks he observed the formation of simple amino acids like glycine, alanine and aspartic acid

Similar Experiments

In 1961, Joan Oro found that amino acids could be made from hydrogen cyanide (HCN) and ammonia in a water solution. He also found that his experiment produced a large amount of the nucleotide base adenine which is one of the four bases in RNA and DNA. It is also a component of ATP, which is a major energy releasing molecule in cells.

Experiments conducted later showed that other RNA and DNA bases could be obtained through simulated prebiotic chemistry (deals with origins of life: how the first molecular building blocks of life were formed and self-assembled into replicating systems) with a reducing atmosphere (an atmosphere characterized by little or no free oxygen but contains hydrogen or hydrogen-containing compounds such as methane or ammonia – the atmospheric conditions believed to be on early Earth).

Other Important Topics

• Theories of Origin of Life Short Notes

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Explain Miller's Experiment ?

An experiment conducted by stanley l. miller and harold c. urey in 1953 provides evidence for the origin of life from inanimate matter. they assembled an atmosphere similar to that thought to exist on early earth [this had molecule like ammonia (nh3), methane (ch4) and hydrogen sulfide, but no oxygen] over water. they maintained the mixture of these gases just below 100 degrees c and passed sparks to simulate lightning. at the end of a weak, 15% of the carbon (from methane) had been converted to simple compounds of carbon including amino acids which make up protein molecules. it indicates the possibility of the origin of life from inanimate matter on the earth, when the atmosphere was reducing (containing no free oxygen), containing gases like methane, ammonia, hydrogen sulfide, frequent lightning and enough water was present. simple amino acids which are building blocks of proteins might have given rise to complex molecules that are building blocks of cells..

What is Miller Urey experiment

• Origin and Evolution of life
• Experimental Evidence by Urey & Miller (1952)
• Active page

Origin and Evolution of life of Class 12

Simulation experiment made in spark–discharge apparatus with H 2 , NH 3 & CH 4 in ratio of 2 : 1 : 2 connected to the flask with boiling water on one hand and condenser on the other hand to cool water vapour to liquid form.

Fig.3.1: Urey & Miller Experiment

Provision of electric spark through tungsten electrodes, supply of radiation and heat energy were made.

Experiment run continuously for 18 days resulted in formation of glycine, alanine and aspartic acid.

Calvin Melvin (1958) irradiated CO 2 and H 2 O directly in a cyclotron and obtained formic acid, succinic acid and oxalic acid.

Origin of life in this prebiotic soup must have needed 3 conditions to fulfill–

• Formation of replicators i.e., self duplicating molecules.
• Replications must have been subjected to error via mutations.
• System of replicators must have required a perpetual source of energy and partial isolation.

These could be explained in further steps :

4 th Step :

The complex molecules in prebiotic soup aggregated to form complex colloidal droplet as prebionts (or protobionts) to fulfill the 3rd (above said) condition of partial isolation. Such aggregates have been artificially produced, which maintain internal environment but are unable to reproduce.

Oparin (1924) called such protobiont as coacervates, Sydney fox (1950) called them microsphere.

Coacervates (protein + polysaccharide + some water) of Oparin showed some metabolism, but had no lipid memberane and  couldn’t reproduce, hence could not be precursor of life. Microspheres formed by mixing  artificially made organic compounds with cool water also had a lipid bilayer. Fox obtained these bodies (1-2 μm) by heating a mixture of few dry amino acids at 130–180ºC and  later cooling them in water, this resembled the size & shape of a coccoid bacteria and could constrict in a process that resembled budding in bacteria. The drawback is that they have limited diversity.

5 th Step :

Nucleic acids are the one to fulfill the 1st requirement i.e. of replicators in prebiotic stage. The experiment yielded purines & pyrimidines which could have formed the nucleotides by random polymerization. But within organisms enzymes (protein) control this process which is formed by transcription→ translation. How could this system have evolved if protein needed nucleic acids to form and nucleic acids required protein to catalyse its replication ? This “chicken–and–egg” puzzle of gene first or metabolism first has an answer if RNA (r-RNA) is considered to have formed first since it has both catalytic and informational properties. The first genetic code would have based on RNA that catalysed its own replication and other chemical reaction e.g., formation of lipid like molecule, proteo-lipid membrane, proteins etc.

One of such formed proteins (enzyme) did play as reverse transcriptase to form DNA from RNA. Then DNA took over the role of genetic material (the blue print) of life.

6 th Step :

The earliest cell (1st living organism) formed were anaerobic heterotrophic prokaryotes. Horowitz (1945) and Orgel (1973) believed that naked gene or present day virus-like form were formed first which then synthesized the likeable molecules around itself from the available raw material in the sea water and then covering by lipid membrane. They obtain energy by anerobic breakdown of organic molecules absorbed from surroundings.

7 th Step :

Before the exhaustion of available organic molecules some heterotrophs might have evolved the property of synthesizing organic molecules first by chemosynthesis and then by photosynthesis.

Chlorophyll like molecule was evolved to trap the sunlight energy, these were the present day Cyanobacteria (blue green algae) like prokaryotes. Emergence of O 2 in photosynthesis was a turning point that changed the reducing atmosphere of earth to oxidising.

8 th Step :

To protect itself from the hostility of O 2 and utilize its potential for generating higher amount of energy more efficient system with membranous organelles i.e., eukaryotes were evolved. There are 2 theories :

• Gradualistic theory or theory of independent origin– As per Oparin’s idea the membranous organelles gradually developed around the specific molecules to form mitochondria, chloroplast and other organelles. Such isolation made the eukaryotes more efficient and so aerobic metabolism of 1 mole of glucose could yield 36 mol. ATP.
• Symbiotic Theory: (Margulis-1964)– believes in formation of eukaryotes by symbiotic association among various kinds of independently existing prokaryotes.Chloroplast and mitochondria like small efficient autotrophic prokaryotes entered the large, less efficient heterotrophic prokaryotes for better protection and supply of raw material, hence all getting benefitted from each other. It became more acceptable after the discovery of DNA and ribosomes inside mitochondria & chloroplasts.
• Theories of Origin of Life
• Origin of Earth
• Introduction of Origin And Evaluation of Life
• First organic molecule formed in the atmosphere was CH4.

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