Final answer:
Fermentation is the last process that can occur to make ATP in the absence of oxygen.
Step-by-step explanation:
In the absence of oxygen, the last process that can occur to make ATP is called fermentation. Fermentation is an important way of making ATP without oxygen and involves glycolysis but not the other two stages of aerobic respiration. This process occurs when cells cannot get enough oxygen to meet their energy needs through aerobic respiration. In the absence of oxygen, the last process that can occur to make ATP is known as fermentation. During fermentation, glycolysis is the first stage and is followed by a pathway that allows for the regeneration of NAD+ from NADH without using oxygen. This is crucial for the continuation of glycolysis, which generates a small amount of ATP. Human muscle cells, many bacteria, and yeasts utilize fermentation to produce ATP when oxygen is not available, resulting in products like yogurt, bread, and wine in the case of yeasts and bacteria, and the build-up of lactate in muscles during intense exercise.