AP BIOLOGY

Detailed explanation-1: -When yeast cells are kept in an anaerobic environment (i.e., without oxygen), they switch to alcoholic fermentation to generate usable energy from food. Like lactic acid fermentation, alcoholic fermentation generates NAD+ so that glycolysis can continue to produce ATP.

Detailed explanation-2: -Alcohol fermentation has two steps: glycolysis and NADH regeneration. During glycolysis, one glucose molecule is converted to two pyruvate molecules, producing two net ATP and two NADH.

Detailed explanation-3: -Without oxygen, some human cells must use fermentation to produce ATP, and this process produces only two molecules of ATP per molecule of glucose. Although fermentation produces less ATP, it has the advantage of doing so very quickly.

Detailed explanation-4: -Fermentation does not require oxygen and is therefore anaerobic. Fermentation will replenish NAD+ from the NADH + H+ produced in glycolysis. One type of fermentation is alcohol fermentation.

Detailed explanation-5: -In the presence of oxygen, yeast undergo aerobic respiration and convert carbohydrates (sugar source) into carbon dioxide and water. In the absence of oxygen, yeasts undergo fermentation and convert carbohydrates into carbon dioxide and alcohol (Figure 2).