Question

Identify a side chain (R) group present in serine, an amino acid.

• A. \(\text{CH}_3-\)
• B. \(\text{H}_3\text{C} - \text{CHOH}-\)
• C. \(\text{Me}_2\text{CH}-\)
• D. \(\text{HO} - \text{CH}_2-\)

Hint:

Serine is a \textbf{hydroxyl-containing amino acid}. Always look for the \(-OH\) group in the side chain to identify it quickly in MCQs.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Amino acids consist of a central carbon atom (the alpha carbon) bonded to an amino group (\(-\text{NH}_2\)), a carboxyl group (\(-\text{COOH}\)), a hydrogen atom (\(-\text{H}\)), and a variable side chain known as the R group. The chemical properties of the amino acid depend on the nature of this R group.
Step 2: Key Formula or Approach:
To identify the correct side chain for serine, recall the standard structures of the 20 common amino acids and match the given R groups to their respective amino acids.
Step 3: Detailed Explanation:
Let's analyze the given side chains:
- (A) \(\text{CH}_3-\) is the side chain for Alanine.
- (B) \(\text{H}_3\text{C} - \text{CHOH}-\) is the side chain for Threonine.
- (C) \(\text{Me}_2\text{CH}-\) (isopropyl group) is the side chain for Valine.
- (D) \(\text{HO} - \text{CH}_2-\) (hydroxymethyl group) is the side chain for Serine.
Therefore, the R group in serine is \(\text{HO} - \text{CH}_2-\).
Step 4: Final Answer:
The correct option is (D).