Answer: Two cysteine residues.
- A Two cysteine residues
- B Two glycine residues
- C Lysine and aspartate
- D Serine and threonine
Correct answer: A. Two cysteine residues
Explanation: Disulfide bonds (S-S) form between the -SH groups of two cysteine residues and stabilise tertiary structure.
Two amino acids join via a condensation reaction: the carboxyl -OH of one and an amine -H of the other are eliminated as water, leaving a peptide bond (-CO-NH-) linking them into a dipeptide; repeating this builds a full protein chain.
Concept context
The chemistry of life: carbohydrates, proteins, lipids, nucleic acids, enzymes, and vitamins. Understand their structures, classification, and biological functions. Highly relevant for NEET and Class 12 board exams.