What process do cells use to release energy without oxygen?

Cells utilize fermentation as a process to release energy without requiring oxygen. This anaerobic process allows cells to generate ATP, the energy currency of the cell, under conditions when oxygen is scarce or unavailable. During fermentation, glucose is partially broken down, and energy is extracted in the form of ATP, alongside byproducts such as lactic acid or ethanol, depending on the type of fermentation.

In contrast, aerobic respiration, which involves the Krebs cycle and cellular respiration, requires oxygen to fully oxidize glucose, leading to the production of significantly more ATP. The Krebs cycle is part of aerobic respiration, contributing to energy production when oxygen is present. This distinguishes fermentation as a crucial alternative energy process that enables organisms to survive in low-oxygen environments.