Correct option is C
Detailed Explanation:
Statement A: HbA1c has glucose attached to the terminal valine in each β chain.
- Correct: HbA1c is a modified form of hemoglobin where glucose attaches to the N-terminal valine in the β chain of hemoglobin. This attachment forms when glucose binds to the hemoglobin molecule, specifically at the N-terminal of the β chain. This process is clinically used to measure long-term blood glucose levels in diabetes.
Statement B: NADH-methemoglobin reductase system in RBC converts methemoglobin to hemoglobin.
- Incorrect: While the NADH-methemoglobin reductase system in RBCs does indeed help convert methemoglobin (Fe³⁺) back to hemoglobin (Fe²⁺), the statement itself is not relevant to the correct combination. In the context of this question, B does not fit with A and C because Statement B is not directly related to the question of HbA1c or oxygen binding to hemoglobin.
Statement C: O₂ binds to the Fe²⁺ in the heme moiety of hemoglobin to form oxyhemoglobin.
- Correct: Oxygen (O₂) binds to the Fe²⁺ (ferrous ion) in the heme group of hemoglobin to form oxyhemoglobin (HbO₂). This is the primary function of hemoglobin in oxygen transport, making this statement correct.
Statement D: The affinity of hemoglobin for O₂ is much higher than that of its affinity for carbon monoxide.
- Incorrect: Carbon monoxide (CO) actually has a much higher affinity for hemoglobin than oxygen (O₂). Hemoglobin binds carbon monoxide more strongly than oxygen, leading to CO poisoning. Therefore, this statement is incorrect.
Correct Answer:
The correct combination of true statements is A and C:
- Statement A: HbA1c forms when glucose binds to the N-terminal valine of the β chain of hemoglobin.
- Statement C: O₂ binds to Fe²⁺ in the heme group of hemoglobin to form oxyhemoglobin.
