What processes do cells use to turn food into usable energy?

Cells convert food into usable energy through cellular respiration, a multi-step process that takes place primarily in the mitochondria of eukaryotic cells. This process involves breaking down glucose and other nutrients to produce adenosine triphosphate (ATP), which is the energy currency of the cell.

During cellular respiration, glucose undergoes a series of biochemical reactions starting with glycolysis, where it is partially broken down in the cytoplasm. This is followed by the Krebs cycle and the electron transport chain in the mitochondria. These steps allow cells to extract energy more efficiently from food, ultimately producing ATP as well as carbon dioxide and water as byproducts.

While fermentation can also lead to the production of energy under anaerobic conditions, it is less efficient than cellular respiration. Photosynthesis is the process used by plants to convert light energy into chemical energy stored in glucose, which is a precursor for respiration, rather than a process used by cells to derive energy from food. Hence, cellular respiration is the primary pathway through which cells harness energy from food molecules.