Question

A yeast cell is transported from an environment with oxygen to a completely oxygen-free environment. Which of the following answer choices best describes the metabolic changes that will occur in the yeast cell? Choose 1 answer: Choose 1 answer: (Choice A) A Glycolysis will still occur and pyruvate will undergo alcohol fermentation, but the Krebs cycle and oxidative phosphorylation will not occur. (Choice B) B Glycolysis will still occur, but pyruvate will not form, causing the yeast cell to undergo alcohol fermentation. (Choice C) C Glycolysis will still occur, pyruvate will still form, causing the yeast cell to undergo lactic acid fermentation. (Choice D) D Glycolysis will not occur and pyruvate will not form, causing the yeast cell to undergo alcohol fermentation.

Answer 1

Choice A

Step-by-step explanation:

Even without oxygen, glycolysis (anaerobic process), will occur as normal and produce pyruvate. Without oxygen, the Krebs cycle and oxidative phosphorylation can't occur, so alcohol fermentation (anaerobic process) will take place instead.

Answer 2

With the presence of glucose, glycolysis will still occur as it is not an oxygen dependent process. Glycolysis will continue to form pyruvate but the pyruvate will not be able to undergo oxidative phosphorylation in the absence of oxygen. Pyruvate will thus be used in alcoholic fermentation or lactic acid fermentation. ( Option A)