Which process do yeast primarily use to generate energy in the absence of oxygen?

Yeast primarily use alcohol fermentation to generate energy in the absence of oxygen. This anaerobic process allows yeast to convert sugars into energy when oxygen is not available. During alcohol fermentation, glucose is broken down into ethanol and carbon dioxide, which releases energy. This is particularly important in environments where oxygen levels are low, allowing yeast to thrive and continue producing energy.

In contrast, other processes like cellular respiration and aerobic respiration require oxygen to break down glucose efficiently, making them unsuitable for anaerobic conditions. Lactic acid fermentation occurs in certain bacteria and animal muscle cells but is not the primary energy-generating process for yeast. Therefore, alcohol fermentation is the optimal choice for yeast under anaerobic circumstances, facilitating their survival and metabolic function in various environments.