Question

Sulphur containing amino acids of the following are
A. Serine
B. Cysteine
C. Lysine
D. Methionine

• A. A, D
• B. A, C
• C. B, C
• D. B, D

Hint:

Remember the structures of the common amino acids, particularly their side chains (R groups). Focus on identifying the presence of a sulfur atom in the R group to classify them as sulfur-containing amino acids. Cysteine and methionine are the primary sulfur-containing amino acids found in proteins.

Answer 1

The Correct Option is D

Amino acids are organic compounds containing an amino group (\( -NH_2 \)), a carboxyl group (\( -COOH \)), and a side chain (R group) that is unique to each amino acid.
We need to identify which of the given amino acids contain sulfur in their side chains (R groups).
A.
**Serine:** The side chain of serine is \( -CH_2OH \).
It does not contain sulfur.
B.
**Cysteine:** The side chain of cysteine is \( -CH_2SH \).
It contains a sulfur atom in the form of a thiol group (\( -SH \)).
C.
**Lysine:** The side chain of lysine is \( -(CH_2)_4NH_2 \).
It does not contain sulfur.
D.
**Methionine:** The side chain of methionine is \( -CH_2CH_2SCH_3 \).
It contains a sulfur atom in the form of a thioether group (\( -S- \)).
Therefore, the sulphur-containing amino acids among the given options are cysteine and methionine.