Q1. [1]
The breakdown of glucose has taken the following pathway :
Glucose →(a) Pyruvate + Energy →(b) Lactic acid + Energy
The sites 'a' and 'b' respectively are :
- (A) Mitochondria and Oxygen deficient muscle cells
- (B) Cytoplasm and Oxygen rich muscle cells
- (C) Cytoplasm and Yeast cells
- (D) Cytoplasm and Oxygen deficient muscle cells
Previously asked in CBSE board exam
2025 31/1/1 Q12
Generated by claude-sonnet-4-6 · 2026-06-11 09:52 · grounding rag
Model Answer
(D) Cytoplasm and Oxygen deficient muscle cells
Step 'a' (Glucose → Pyruvate) occurs in the cytoplasm (glycolysis). Step 'b' (Pyruvate → Lactic acid) occurs in oxygen-deficient muscle cells during anaerobic respiration.
Explanation
- Glycolysis always occurs in the cytoplasm — this is a fixed fact examiners test repeatedly.
- Lactic acid fermentation is specific to oxygen-starved muscle cells (not yeast — yeast produces ethanol + CO₂).
- Options B and C are wrong because aerobic/yeast pathways don't produce lactic acid.
- Option A is wrong because glycolysis does NOT occur in mitochondria.
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