GRE Subject Test: Chemistry : Proteins

Study concepts, example questions & explanations for GRE Subject Test: Chemistry

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Example Questions

Example Question #3 : Macromolecule Structures And Functions

How many water molecules are lost from the condensation of 100 amino acids into a polypeptide?

Possible Answers:

Correct answer:

Explanation:

A peptide bond is formed via the condensation of one amino acid's alpha-carboxy group with the alpha-amino group of another amino acid. Thus, the joining together of two amino acids results in the loss of one water molecule. Likewise, joining three amino acids together results in the loss of two water molecules. Following this pattern, we can conclude that the number of water molecules lost is equal to the number of amino acids joined together, minus 1. Therefore, the joining together of 100 amino acids results in the loss of 99 water molecules.

Example Question #1 : Biochemistry

 

An enzyme that cleaves disulfide bridges would most disrupt a protein containing which amino acid sequence?

Possible Answers:

All of the answers would be equally affected

Tyr–Cys–Val–Val–Leu–Thr

Cys–Leu–Val–Tyr–Tyr–Thr

Val–Leu–Leu–Cys–Tyr–Thr

Tyr–Cys–Cys–Thr–Val–Leu

Correct answer:

Tyr–Cys–Cys–Thr–Val–Leu

Explanation:

Disulfide bridges are made between two cysteine amino acids. An enzyme that cleaves disulfide bonds would disrupt a protein containing the most cysteine residues; therefore, Tyr–Cys–Cys–Thr–Val–Leu is the correct answer.

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