Which of the following statements about cystine is correct?
A
Cystine is formed through a peptide linkage between two cysteines.
B
Cystine forms when the -CH2-SH group is oxidized to form a -CH2-S-S-CH2- disulfide bridge between 2 cysteines.
C
Cystine is formed by the oxidation of the carboxylic acid groups on two cysteines.
D
Two cystines are released when a -CH2-S-S-CH2- disulfide bridge is reduced to -CH2-SH.
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1
Understand the structure of cysteine: Cysteine is an amino acid with a thiol group (-SH) attached to its side chain.
Recognize the process of oxidation: In biochemistry, oxidation often involves the loss of electrons or the formation of disulfide bonds.
Identify the formation of cystine: Cystine is formed when two cysteine molecules undergo oxidation, resulting in the formation of a disulfide bond (-S-S-) between their thiol groups.
Clarify the disulfide bridge: The disulfide bridge in cystine is represented as -CH2-S-S-CH2-, linking two cysteine residues.
Understand reduction of disulfide bonds: When a disulfide bridge is reduced, it breaks into two thiol groups (-SH), regenerating the original cysteine molecules.