. Explain Miller-Urey Experiment of Chemical Evolution with diagram

Best Answer

MillerUrey Experiment:

i. An early attempt to see what kinds of organic molecules might have been produced on the early earth was carried out in 1953 by Stanley L. Miller and Harold C. Urey. In what has become a classic experiment, they attempted to reproduce the conditions in the earth's primitive oceans under a reducing atmosphere. To carry out their experiment, Miller and Urey

ii. Assembled a reducing atmosphere rich in hydrogen and excluding gaseous oxygen.

iii. Simulated lightning by bombarding it with energy in the form of sparks.

iv. Miller sealed in a spark chamber a mixture of water (H2O). methane (CH4), ammonia (NH3) and hydrogen gas (H2).

v. The ratio of CH4, NH3, H2 were 2 : 1 : 2.

vi. Electric sparks of 75,000 volt was provided to the mixture.

vii. The spark chamber was connected to another flask with the arrangement for boiling water (provision for evaporation).

viii. The other end of the spark chamber was connected to a trap by a tube that passed through a condenser (an arrangement for condensation and collection of aqueous solution, equivalent to rain and Haldane's soup).

ix. The trap, in turn, was connected with the flask for boiling water (arrangement for circulation).


Result of Miller's Experiment:

They found that within a week, 15% of the carbon originally present as methane gas (CH4) had converted into other simple carbon compounds. Among these compounds were formaldehyde (CH2O) and hydrogen cyanide (HCN). These compounds then combined to form simple molecules, such as formic acid (HCOOH) and urea (NH2CONH2), and more complex molecules containing carbon-carbon bonds, including the amino acids glycine and alanine.

In similar experiments performed later by other scientists, more than 30 different carbon compounds were identified, including the amino acids glycine, alanine, glutamic acid, valine, proline, and aspartic acid. Other biologically important molecules were also formed in these experiments. For example, hydrogen cyanide contributed to the production of a complex ring-shaped molecule called adenine-one of the bases found in DNA and RNA. Thus, the key molecules of life could have formed in the atmosphere of the early earth.



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