Question

In saturated condition, 1g of haemoglobin can carry approximately

• A. 1.3 ml of oxygen
• B. 0.5 ml of oxygen
• C. 2.5 ml of oxygen
• D. 5 ml of oxygen

Hint:

Hüfner's Constant: $1\text{ g Hemoglobin} = 1.34\text{ mL } \text{O}_2$ (at $100\%$ saturation).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Hüfner's oxygen-binding constant defines the theoretical and empirical stoichiometric oxygen-binding capacity per gram of hemoglobin.
Key Formula or Approach:
\[ 1\text{ mole Hb (64,458 g)} = 4\text{ moles } \text{O}_2 (4 \times 22,400\text{ mL}) \implies \frac{89,600}{64,458} \approx 1.39\text{ mL/g} \xrightarrow{\text{Empirical In Vivo}} 1.34\text{ mL/g} \]

Step 2: Detailed Explanation:
Stoichiometry of hemoglobin oxygenation:
- One tetrameric hemoglobin molecule ($ ext{MW} \approx 64,500\text{ Da}$) contains four heme iron ($ ext{Fe}^{2+}$) moieties, binding a maximum of $4\text{ molecules of } \text{O}_2$.
- Pure theoretical binding yields $1.39\text{ mL } \text{O}_2 / \text{g Hb}$.
- Under physiological conditions in blood (accounting for minor inactive fractions like methemoglobin and carboxyhemoglobin), the universally accepted empirical standard (Hüfner's constant) is $1.34\text{ mL of \text{O}_2 / \text{g Hb}$ (approximated as $1.3\text{ mL}$)}.

Step 3: Final Answer:
Hence, 1g of hemoglobin carries approximately 1.3 ml of oxygen, corresponding to option (A).