Q47.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A:
Hemoglobin binding to oxygen is non-cooperative.
Reason R:
Hemoglobin is the oxygen carrier.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Both A and R are correct and R is the correct explanation of A
(2) Both A and R are correct but R is not the correct explanation of A
(3) A is correct but R is not correct
(4) A is not correct but R is correct
Hemoglobin oxygen binding is cooperative, not non-cooperative, making Assertion A false while Reason R is true. The correct answer is option (4): A is not correct but R is correct.
Question Breakdown
This assertion-reason question tests knowledge of hemoglobin’s oxygen-binding properties. Hemoglobin, a tetrameric protein in red blood cells, transports oxygen from lungs to tissues.
Option Analysis
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Option (1): Both A and R correct, R explains A. Incorrect—Assertion A is false since hemoglobin shows cooperative binding.
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Option (2): Both correct, R doesn’t explain A. Incorrect—Assertion A false.
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Option (3): A correct, R false. Incorrect—R true (hemoglobin carries oxygen), but A false.
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Option (4): A false, R true. Correct—cooperative binding yields sigmoidal curve; R unrelated to cooperativity.
Hemoglobin binding to oxygen is non-cooperative? Think again—this common misconception trips up NEET aspirants in assertion-reason questions. In this detailed guide, we decode hemoglobin binding to oxygen is non-cooperative (Assertion A) versus its true cooperative nature, Reason R (oxygen carrier), and why option (4) wins.
Hemoglobin’s Cooperative Magic
Hemoglobin, a tetramer with four heme groups, exhibits positive cooperativity: initial O₂ binding shifts T (tense, low-affinity) to R (relaxed, high-affinity) state, easing subsequent bindings. This creates a sigmoidal dissociation curve—ideal for lung loading and tissue unloading—unlike myoglobin’s hyperbolic non-cooperative curve.
Assertion A wrongly claims non-cooperative binding, which would yield hyperbolic kinetics. Reality: cooperativity (Hill coefficient ~2.8) ensures efficiency.
Why R Fails Explanation
Reason R states hemoglobin carries oxygen—true, binding up to 4 O₂ reversibly. But it doesn’t explain (or refute) cooperativity; it’s just a function description.
Exam Strategy for Assertion-Reason
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Verify each statement independently.
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Check if R causally links to A.
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NEET tip: Recall sigmoidal vs hyperbolic for cooperativity.
Master hemoglobin binding to oxygen is non-cooperative myths for scoring in Breathing & Exchange of Gases chapter.
