Which process do cells use to create energy from glucose in the absence of oxygen?

Cells use fermentation to create energy from glucose in the absence of oxygen, which is crucial for survival in anaerobic conditions. During fermentation, glucose undergoes partial oxidation, leading to the production of ATP, which is the energy currency of the cell, along with byproducts such as ethanol or lactic acid, depending on the type of organism and the specific fermentation process.

Fermentation allows cells to continue generating energy when oxygen is not readily available, as opposed to aerobic cellular respiration, which requires oxygen to completely breakdown glucose into carbon dioxide and water, producing a larger amount of ATP. Photosynthesis, on the other hand, is the process used by plants and some microorganisms to convert light energy into chemical energy, which does not directly relate to energy production in the absence of oxygen. Glycolysis is the first step in both fermentation and aerobic respiration, breaking down glucose into pyruvate, but it does not encompass the full energy-generating process that occurs without oxygen. Thus, fermentation is the essential process for energy production under anaerobic conditions.