Question

Which of the following is a thiol-containing amino acid?

• A. Cysteine
• B. Glycine
• C. Serine
• D. Tryptophan

Hint:

Cysteine forms disulfide bonds, which are strong covalent bonds that can stabilize the tertiary and quaternary structure of proteins by linking two cysteine residues together.

Answer 1

The Correct Option is A

Cysteine is a sulfur-containing amino acid featuring a thiol (-SH) group in its side chain. This group plays critical roles in protein chemistry:
• Forms disulfide bonds (-S-S-) during oxidation, stabilizing protein structures.
• Participates in catalytic activity in enzyme active sites.
Cysteine’s unique properties make it indispensable in maintaining protein structure and function.