How do mitochondria provide energy for cell activities?

Mitochondria, often called the "powerhouses of the cell," provide energy for cellular activities by producing adenosine triphosphate (ATP) through a process known as cellular respiration.1

The production of ATP occurs primarily through three metabolic stages: glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation. During these stages, energy derived from the breakdown of food molecules is captured in electron carriers like NADH and FADH${}_2$.12

These carriers donate electrons to the electron transport chain, a series of protein complexes embedded in the mitochondrial cristae. As electrons move down this chain, the energy released is used to pump protons across the inner mitochondrial membrane, creating an electrochemical gradient.32

Finally, protons flow back into the mitochondrial matrix through an enzyme complex called ATP synthase. This flow provides the energy necessary to synthesize ATP from ADP and phosphate. Once produced, ATP acts as a shuttle, delivering chemical energy to fuel various energy-consuming cellular processes, such as mechanical work and transport.432