Question

Which one of the following amino-acids was not found to be synthesized in Miller’s experiment?
A. Glycine
B. Aspartic acid
C. Glutamic acid
D. Alanine

Answer 1

The Miller and Urey experiment was done in 1952 to understand the conditions that might have led to the origin of life on earth. They simulated the environmental conditions persistent in early periods of origin of life. Water, methane, ammonium, and hydrogen were thought to be a major element in the earth’s atmosphere. Carbon was also involved that changed into amino acids.

Complete answer: The basic idea behind the experiment of Miller and Urey was that inorganic matter formed amino acids, the basic unit of all living matter in the early earth’s atmosphere. They performed a simulation of the early earth’s atmosphere to understand the origin of life on Earth. An apparatus was set involving sterile glass tubes connected with flasks in a loop. This apparatus was filled with four major components that Miller and Urey thought are the basic elements present in the early Earth’s atmosphere. These chemicals were methane, water, hydrogen, and ammonium. One of the glass flasks was half-filled with water. The other flask contained a pair of electrodes that sparked electricity to imitate the lighting condition of the early earth. The water vapor was heated and released to be mixed with a chemical mixture of hydrogen, methane, and ammonium. The released gases have circulated the apparatus to resemble the earth’s atmosphere. Later the vapors were cooled down and the water was condensed. The condensed water was circulated back in the first flask containing water in a continuous cycle. This process was repeated for a week and then the two scientists observed that $10-15$ carbon converted into organic compounds. Out of this $2$ converted and formed 13 amino acids including alanine, glycine, and aspartic acid but not Glutamic acid.
So, from the above discussion, option C is the correct answer. Glutamic acid was not found to be formed in Miller’s experiment.

Note: Miller’s experiment was highly criticized by a few scientists. They were of the view that the gases released by volcanic eruptions like carbon dioxide, oxygen, nitrogen, etc were the major components of the early Earth’s atmosphere and not the gases used by Miller and Urey. Also, the experiment failed to describe how proteins were responsible for amino acid formation.