Question

Carbaminohemoglobin releases \(\text{CO}_2\) into lungs due to

(A). Low \(\text{pCO}_2\)
(B). Higher \(\text{pO}_2\)
(C). High affinity for \(\text{O}_2\)
(D). Low pH

Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

At the lungs (alveoli):
- High \(\text{pO}_2\), Low \(\text{pCO}_2\), and High pH promote \(\text{O}_2\) loading and \(\text{CO}_2\) unloading.
At the tissues:
- Low \(\text{pO}_2\), High \(\text{pCO}_2\), and Low pH promote \(\text{O}_2\) unloading and \(\text{CO}_2\) loading.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Gas exchange in the lungs is driven by partial pressure gradients and the Haldane effect, which describes how oxygen binding to hemoglobin reduces its affinity for carbon dioxide.

Step 2: Detailed Explanation:
In the capillaries of the lungs (alveolar interface):
- Statement (A): The partial pressure of carbon dioxide (\(\text{pCO}_2\)) in the alveoli is lower than in the blood, creating a gradient that drives the dissociation and release of \(\text{CO}_2\) from carbaminohemoglobin. Thus, (A) is correct.
- Statement (B): The partial pressure of oxygen (\(\text{pO}_2\)) is high, causing \(\text{O}_2\) to bind to hemoglobin. Thus, (B) is correct.
- Statement (C): Oxygen binding to hemoglobin induces a conformational change that reduces hemoglobin's affinity for \(\text{CO}_2\) and protons (Haldane effect), forcing the release of bound \(\text{CO}_2\). Thus, (C) is correct.
- Statement (D): At the lungs, blood pH is relatively high (alkaline) due to the removal of \(\text{CO}_2\). Low pH (acidic) occurs in systemic tissues to promote oxygen release (Bohr effect). Thus, (D) is incorrect.
Therefore, (A), (B), and (C) are correct.

Step 3: Final Answer:
The correct option is 2, which corresponds to (A), (B) and (C) only.