Final answer:
No, yeast does not undergo lactic acid fermentation; instead, it undergoes alcoholic fermentation in the absence of oxygen, yielding ethanol and carbon dioxide.
Step-by-step explanation:
No, in the absence of oxygen, yeast typically undergoes alcoholic fermentation, not lactic acid fermentation, to produce ethanol and carbon dioxide.
Fermentation is a type of anaerobic respiration that occurs when oxygen is scarce. Yeast, which are facultative anaerobes, prefer to perform alcoholic fermentation under these conditions. During this process, glucose is converted into ethanol (CH3CH2OH) and carbon dioxide (CO₂) through glycolysis. This transformation enables the regeneration of NAD+ from NADH, allowing glycolysis to continue and ATP to be produced, albeit in much smaller amounts than would be through aerobic respiration. This form of fermentation is utilized in the creation of bread, beer, and wine. The carbon dioxide produced helps bread to rise, and the ethanol contributes to the alcoholic content in beverages. Yeasts do have the capability to survive in various oxygen levels, but they do not perform lactic acid fermentation as this is typically seen in animal muscle cells under anaerobic conditions or in certain bacteria. Lactic acid fermentation results in lactate, and while used by humans in certain scenarios, it is not the pathway yeast employ to cope with an anaerobic environment.