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When yeast cells are O₂ starved, fermentation serves as the source of

June 1, 2025 by rawan239

When yeast cells are O₂ starved, fermentation serves as the source of energy. This results in the production of :

ATP + CO₂ + Ethanol

ATP + O₂ + Pyruvate

ATP + CO₂ + Lactic acid

ATP + O₂ + Acetaldehyde

This question was previously asked in

UPSC NDA-1 – 2023

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When yeast cells are deprived of oxygen, they switch from aerobic respiration to anaerobic fermentation to regenerate NAD⁺ needed for glycolysis. Glycolysis is the initial stage where glucose is broken down into pyruvate, producing a small amount of ATP. In alcoholic fermentation, pyruvate is converted into acetaldehyde and then ethanol, with the release of carbon dioxide. The net products from the glucose under oxygen-starved conditions undergoing fermentation by yeast are ATP (produced during glycolysis), CO₂, and Ethanol.

– Yeast undergoes alcoholic fermentation under anaerobic conditions.
– Fermentation allows glycolysis to continue by regenerating NAD⁺.
– Glycolysis produces ATP.
– Pyruvate is converted to acetaldehyde and then ethanol during alcoholic fermentation, releasing CO₂.

Lactic acid fermentation is another type of fermentation that occurs in muscle cells and some bacteria, producing lactic acid instead of ethanol and CO₂. The primary purpose of fermentation is not to directly produce large amounts of ATP but to regenerate the NAD⁺ consumed during glycolysis, allowing ATP production via glycolysis to continue in the absence of oxygen.

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