Question

Match List-I with List-II
List-I (Condition)
(A). The addition of $\text{H}^+$ to a suspension of RBCs results in
(B). The RBC of mammals living in high altitude exhibit
(C). RBCs of rats and dogs with $\text{Mg}$ deficiency
(D). Oxy Hb with a relaxed structure
List-II (Effect)
(I). Lower glycolytic rates
(II). Greater Hb $\text{O}_2$ affinity
(III). Decrease $\text{O}_2$ affinity of Hb
(IV). Lowered binding capacity for $\text{CO}_2$
Choose the correct answer from the options given below:

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (I), (B) - (II), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (II), (D) - (I)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Remember the Bohr Effect:
Increasing $\text{H}^+$ (lower pH) and $\text{CO}_2$ concentration shifts the hemoglobin curve to the right, meaning decreased oxygen affinity, facilitating oxygen unloading in working tissues.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Hemoglobin (Hb) oxygen affinity is dynamically regulated by physiological factors such as pH, carbon dioxide concentration, temperature, and specific organic phosphates (such as 2,3-BPG).
This coordinate regulation is essential for efficient oxygen uptake in the lungs and delivery to metabolizing tissues.

Step 2: Detailed Explanation:
Let us analyze each condition and its corresponding physiological effect:
- (A) Addition of $\text{H}^+$ to a suspension of RBCs: Increasing $\text{H}^+$ concentration (decreasing pH) stabilizes the Tense (T) state of hemoglobin through the protonation of specific amino acid residues.
This promotes the release of oxygen, shifting the oxygen-dissociation curve to the right, which represents a decrease in the $\text{O}_2$ affinity of Hb (III) (the Bohr effect).
- (B) RBC of mammals living at high altitude: High-altitude adaptation can involve specialized mechanisms. To prevent hyperventilation-induced respiratory alkalosis from drastically altering blood gas transport, their RBCs exhibit a lowered binding capacity for $\text{CO}_2$ (IV).
- (C) RBCs with $\text{Mg}$ deficiency: Magnesium ($\text{Mg}^{2+}$) is a critical obligate cofactor for several key enzymes in glycolysis (such as hexokinase and phosphofructokinase), which require Mg-ATP complexes. Thus, $\text{Mg}$ deficiency results in lower glycolytic rates (I) in red blood cells.
- (D) Oxy Hb with a relaxed structure: Oxygenated hemoglobin adopts the Relaxed (R) state, which exhibits a greater $\text{O}_2$ affinity (II) compared to the deoxygenated Tense (T) state.
Matching these gives: (A) - (III), (B) - (IV), (C) - (I), (D) - (II).

Step 3: Final Answer:
The matching sequence corresponds to option (D).