How do cells turn food into energy?

The energy that comes from our food is used by cells to create and preserve the biological order that allows them to survive.

As food is broken down during digestion, its various components are broken down into simpler monomers or subunits: proteins become amino acids, polysaccharides become simple sugars, and fats become fatty acids and glycerol. These building blocks are then absorbed by the individual cells and used for energy and storage, respectively.

However, the majority of animal cells produce energy primarily through the breakdown of glucose (sugar).

Cells turn food into energy through a process called cellular respiration, which occurs in three main stages: glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain). During glycolysis, glucose is broken down into pyruvate, producing a small amount of ATP and NADH. Pyruvate then enters the citric acid cycle, where it is further oxidized, generating more ATP, NADH, and FADH2. Finally, in oxidative phosphorylation, electrons from NADH and FADH2 are transferred through a series of protein complexes, creating a proton gradient across the inner mitochondrial membrane. This gradient drives ATP synthesis as protons flow back through ATP synthase. Overall, cellular respiration converts the chemical energy stored in food molecules into ATP, the cell's primary energy source.