Correct option is D
Explanation-
Hemoglobin (HbA) has 2 α-chains and 2 β-chains. In diabetes, excess glucose in blood reacts non-enzymatically with the N-terminal valine of the β-chain. This forms a Schiff base initially, which later undergoes rearrangement into a stable ketoamine structure , this process is called glycation. Hemoglobin A1c (HbA1c) is a modified form of normal adult hemoglobin (HbA). It is used clinically to measure long-term blood sugar (glucose) levels. HbA1c is formed when glucose molecules in the blood attach to hemoglobin, the oxygen-carrying protein in red blood cells.
Step-by-Step Mechanism of HbA1c Formation:
1. Glucose in blood (open-chain form) reacts with the free amino group (–NH2) at the N-terminal valine of the β-globin chain.
2. This forms a Schiff base (aldimine):
Val–NH2 + Glucose (CHO group) → Val–N=CH–Glucose
3. The Schiff base undergoes Amadori rearrangement to form a stable ketoamine structure → This stable molecule is called HbA1c.
So, the correct answer is option D - Valine of each β chain
