# DBT JRF 2022 — Question 35

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Amino Acid Structure & Properties · Difficulty: Medium

## Question

Which of the following are the sulfur containing amino acids? i. Methionine ii. Histidine iii. Leucine iv. Cysteine

## Options

- **A.** (ii) and (i)
- **B.** (i) and (iv)
- **C.** (iv) and (ii)
- **D.** (iii) and (ii)

## Answer

Option B

## Explanation

Sulfur-containing amino acids: Among the 20 standard amino acids, only two contain sulfur: 1. Methionine (Met, M): Contains a thioether group ( $-\text{S-CH}_3$ ) in its side chain. It is the universal start amino acid. 2. Cysteine (Cys, C): Contains a thiol group ( $-\text{SH}$ ) in its side chain. Can form disulfide bonds ( $-\text{S-S}-$ ) with another Cys, important for protein tertiary structure. Amino acids without sulfur: • Histidine: Contains an imidazole ring (N-containing); no sulfur. • Leucine: A branched-chain aliphatic amino acid with only C, H; no sulfur. Answer: Methionine and Cysteine (the option containing Met/Cys).

Source: https://mypyqbuddy.com/questions/which-of-the-following-are-the-sulfur-containing-6a104cd5920734408bc0c732