Question

Consider the following amino acids:
•[(i)] Lysine
•[(ii)] Glutamine
•[(iii)] Arginine
•[(iv)] Leucine
•[(v)] Serine
•[(vi)] Proline
•[(vii)] Valine Which of the given amino acids are basic in nature?

• A. (i) and (iii)
• B. (i), (ii) and (iv)
• C. (iii) and (vii)
• D. (iii), (v) and (vi)

Hint:

Basic amino acids: Lysine, Arginine, Histidine.
Acidic amino acids: Aspartic acid, Glutamic acid.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Amino acids are classified as acidic, basic, or neutral based on the relative number of amino (\(-NH_{2}\)) and carboxyl (\(-COOH\)) groups in their structure. Basic amino acids contain more amino groups than carboxyl groups.
Step 2: Key Formula or Approach:
Basic amino acids have a side chain containing a nitrogenous base (amino, guanidino, or imidazole group).
: Detailed Explanation:
1. Lysine (i): Contains an additional \(\epsilon\)-amino group in its side chain. It is basic.
2. Arginine (iii): Contains a guanidino group in its side chain, which is highly basic. It is basic.
3. Histidine (not in list): Contains an imidazole group. It is also basic.
4. Others:
- Glutamine: Polar neutral (contains an amide group).
- Leucine, Valine: Non-polar neutral (hydrocarbon side chains).
- Serine: Polar neutral (contains a hydroxyl group).
- Proline: Neutral cyclic amino acid.
Step 3: Final Answer:
Only (i) Lysine and (iii) Arginine are basic. The correct option is (A).