Fermentation & Pyruvic Acid Conversion — NEET Biology
✅ Asked in NEET 2025Which of the following is correct about the end product of glycolysis and its further fate in yeast? NEET 2025
Which of the following is correct about the end product of glycolysis and its further fate in yeast? NEET 2025
Answer & NCERT explanation
Correct answer: B — Pyruvate is reduced to ethanol and CO₂ under anaerobic conditions
In yeast under anaerobic conditions, pyruvate from glycolysis undergoes alcoholic fermentation. Pyruvate is first decarboxylated to acetaldehyde by pyruvate decarboxylase, then acetaldehyde is reduced to ethanol by alcohol dehydrogenase. This regenerates NAD+ needed for glycolysis continuation. CO2 is released during decarboxylation.
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In fermentation, say by yeast, the incomplete oxidation of glucose is achieved under anaerobic conditions by sets of reactions where pyruvic acid is converted to CO₂ and ethanol. The enzymes, pyruvic acid decarboxylase and alcohol dehydrogenase catalyse these reactions. Other organisms like some bacteria produce lactic acid from pyruvic acid. The steps involved In animal cells also, like muscles during exercise, when oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate dehydrogenase. The reducing agent is NADH+H⁺ which is reoxidised to NAD⁺ in both the processes.
NTA tests students on what happens to pyruvic acid under anaerobic conditions in different organisms. In yeast, pyruvic acid is converted to CO₂ and ethanol (alcoholic fermentation), while in bacteria and muscles it forms lactic acid (lactate fermentation). The key trap: students confuse which organism produces which product, or forget that NADH+H⁺ acts as the reducing agent in both pathways. Remember: alcoholic fermentation = yeast/plants (CO₂ + ethanol), lactic fermentation = muscles/bacteria (lactic acid). Both require NADH oxidation to regenerate NAD⁺ for continued glycolysis.
What does NCERT say about fermentation say by yeast?
Has this concept appeared in NEET?
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Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
88/90MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.