Q.45 Given below are two statements : One is labelled as Assertion (A) and the other is
labelled as Reason (R).
Assertion (A) :In a healthy body RBCs can live for several months or years.
Reasons (R) :RBCs are responsible for transportation of oxygen and some
amount of carbon dioxide also.
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
Both (A) and (R) are correct but (R) is NOT the correct explanation of (A), making option (2) correct.
RBCs live ~120 days (several months), but their oxygen transport function doesn’t explain why—they lack nuclei/mitochondria to minimize energy use and maximize circulation time.
Question Breakdown
Assertion-reason tests physiological fact vs. causal logic. (A) states accurate RBC lifespan; (R) correctly describes function. However, O₂/CO₂ transport doesn’t cause longevity—structural adaptations (biconcave shape, no organelles) do.
Option Analysis
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(1) Both correct, (R) explains (A): Incorrect; RBC function (R) doesn’t determine lifespan (A)—anucleate design enables 120-day circulation.
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(2) Both correct, (R) NOT explanation: Correct; both facts true, but no causal link—lifespan results from membrane flexibility, spectrin cytoskeleton, not transport role.
-
(3) (A) correct, (R) incorrect: Incorrect; (R) accurately states primary RBC functions.
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(4) (A) incorrect, (R) correct: Incorrect; (A) matches established 100-120 day average.
RBCs healthy body lifespan assertion reason questions test causal vs. correlative logic for GATE Life Sciences. Mature erythrocytes circulate ~120 days before splenic clearance, independent of their oxygen/CO₂ transport role.
RBC Longevity Factors
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Anucleate: No DNA repair/energy needs → stable hemoglobin.
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Spectrin cytoskeleton: Maintains biconcave shape through capillaries.
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Enzyme-deficient: Low metabolism preserves ATP for Na⁺/K⁺-ATPase.
AR Logic Breakdown
| Statement | Fact | Explains Lifespan? |
|---|---|---|
| A: RBCs live months | ✓ 120 days average | N/A |
| R: O₂/CO₂ transport | ✓ Function | ✗ No causal link |
Clearance Mechanism
Day 120: PS exposure → macrophage phagocytosis (spleen/liver). ~5 million RBCs/second recycled without hemolysis.
Exam Strategy
GATE AR traps assume function = longevity cause. Key: Distinguish “what they do” vs. “why they last.” Lifespan = structural adaptation for circulation efficiency, not transport requirement.
