Which of the following pairs of amino acids are related by a simple redox reaction?

Options

A. Cysteine and cystine
B. Methionine and serine
C. Leucine and isoleucine
D. Alanine and valine

Answer

A

Explanation

The `-SH` group of cysteine makes cysteine a thiol. One property of thiols is that they can be converted to disulphides by mild oxidizing agents. Moreover, this conversion can be reversed by mild reducing agent.
`underset("Thiol")(2R-S-H)overset(overset([O])larr)underset([H])rarr underset("Disulphide")(R-S-S-R)`
`2HO_(2)C underset("Cysteine")(underset(NH_(2))underset(|)(C))HCH_(2)SH overset(overset([O])rarr)underset([H])larrHO_(2)C underset("Cystine")(underset(NH_(2))underset(|)(C)HCH_(2)S-SCH_(2)underset(NH_(2))underset(|)(C)HCO_(2)H)`
It is the disulphide linkage between cysteine units in a protein chain that contributes to the overall structure and shape of the protein.