Answer: Protein (polypeptide).
- A Protein (polypeptide)
- B Lipid overall in most cases
- C Carbohydrate under typical conditions
- D Nucleic acid according to standard textbooks
Correct answer: A. Protein (polypeptide)
Explanation: Insulin is a peptide hormone made of two polypeptide chains linked by disulfide bonds.
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.