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Question #46334

Difficulty: 8/10 | 🟢 Free

The Question

A patient rescued from a closed garage with a running car engine exhibits severe tissue hypoxia, despite having a normal arterial partial pressure of oxygen ( $pO_2$ ). Which of the following statements most accurately describes the physiological effect of carbon monoxide (CO) on their oxygen-haemoglobin dissociation curve?

Options

A.
The curve shifts to the right, increasing the $P_{50}$ value to compensate for hypoxia by promoting oxygen release to systemic tissues.
B.
The maximum oxygen saturation plateau is lowered, and the curve shifts to the left, severely impairing the release of bound oxygen to systemic tissues.
C.
CO binds to the amino groups of the globin chain, altering its conformation and shifting the curve to the right similar to the Bohr effect.
D.
The curve maintains its normal sigmoidal shape and $P_{50}$ value, but the total oxygen-carrying capacity is reduced purely by competitive inhibition at the heme sites.

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Comparative_Analysis

Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.

Concepts Behind This Question

Hemoglobin-CO2 Binding Sites|Antibody Structure Logic|Oxygen-Hemoglobin Dissociation Curve

Why This Question Is Tricky

Common Mistakes

Conceptual Pivot: Students frequently confuse the physiological effects of Carbon Dioxide ( $CO_2$ ) with Carbon Monoxide (CO).

While high $CO_2$ causes a right shift (Bohr effect) to facilitate oxygen unloading, CO causes a left shift.

The trap lies in assuming that because CO causes hypoxia, the body will automatically shift the curve right to compensate.

In reality, CO's allosteric effect on haemoglobin locks the remaining oxygen in place, creating a lethal 'double hit': reduced carrying capacity and failure to unload.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Breathing and Exchange of Gases - Class 11
Concept	Hemoglobin-CO2 Binding Sites
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free