Answer: R group (side chain).
- A R group (side chain)
- B Amino group
- C Carboxyl group
- D Alpha carbon
Correct answer: A. R group (side chain)
Explanation: The R group (side chain) is unique to each amino acid and determines its chemical and physical properties.
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.