JEE Main 2023 · 31 January · morning · Single correct · +4 / −1
A protein 'X' with molecular weight of 70,000 u, on hydrolysis gives amino acids. One of these amino acid is
- (a) NH₂-CH₂-CH-CH₂CH₂COOH
- (b) CH₃; |; CH₃, -, C, -, CH₂, -, CH₂COOH; |; NH₂
- (c) CH₃-C(CH₃; |)H-CH₂-CH-COOH
- (d)
Answer and solution
Answer (c) CH₃-C(CH₃; |)H-CH₂-CH-COOH
Solution
Chemistry ma’am · 3 steps
Proteins break down only into α-amino acids, so find the option with NH₂ on the carbon next to COOH.
- What hydrolysis gives. A protein is a chain of amino acids joined by peptide bonds. Hydrolysis breaks these bonds and releases α-amino acids, where NH₂ and COOH sit on the same carbon.
- Number from COOH. Call the carbon right next to COOH the α carbon, then β, γ and δ as you move away. Check where NH₂ sits in each option.
Option Carbon carrying NH₂ Type (a) 4th carbon from COOH δ-amino acid (b) 3rd carbon from COOH γ-amino acid (c) carbon next to COOH α-amino acid (leucine) (d) 2nd carbon from COOH β-amino acid - So. Only (c), (CH₃)₂CH-CH₂-CH(NH₂)-COOH, is an α-amino acid. It is leucine, a natural amino acid that proteins give on hydrolysis.
The idea to keep. Every amino acid in a protein is an α-amino acid, with NH₂ on the carbon right next to COOH. The molecular weight of the protein does not matter here.
Answer from the NTA final answer key. Solution by PrepWiser.