How does food energy become usable energy for cells?

Food energy becomes usable energy for cells through the process of cellular respiration. This biological process allows cells to convert the chemical energy stored in food, such as glucose, into adenosine triphosphate (ATP), which serves as the primary energy currency of the cell.

During cellular respiration, glucose and oxygen are taken in by the cell. These substances undergo a series of enzymatic reactions that break down glucose in the presence of oxygen, ultimately releasing energy. The process typically consists of several stages, including glycolysis, the Krebs cycle, and the electron transport chain, which collectively produce ATP.

This conversion of food energy into a usable form enables cells to perform various functions necessary for life, such as growth, repair, and maintenance of cellular processes. In contrast, photosynthesis, fermentation, and glycolysis serve different roles. Photosynthesis primarily occurs in plants and algae, converting light energy into chemical energy, while fermentation is an anaerobic process that can produce energy without oxygen, and glycolysis is just the initial step in cellular respiration that breaks down glucose into pyruvate. Thus, cellular respiration is the comprehensive process that ultimately transforms food energy into a form readily usable by cells.