The primary function of mitochondria is to generate the chemical energy required to power most of the cell's biochemical reactions. This energy is produced in the form of adenosine triphosphate (ATP), which acts as the energy currency of the cell

. Mitochondria achieve this through aerobic respiration, involving the citric acid cycle (Krebs cycle) and oxidative phosphorylation. The inner mitochondrial membrane contains protein complexes of the electron transport chain (ETC) that facilitate a series of redox reactions, creating a proton gradient used by ATP synthase to produce ATP from ADP

. Beyond energy production, mitochondria also:

• Store calcium ions for cell signaling
• Generate heat
• Regulate cell growth and programmed cell death (apoptosis)
• Participate in metabolic regulation and cellular signaling pathways
• Influence aging processes and cellular differentiation

Mitochondria have a double membrane structure: an outer membrane permeable to small molecules and an inner membrane folded into cristae where the ETC and ATP synthesis occur. They contain their own DNA, allowing some degree of autonomous function and maternal inheritance

. In summary, mitochondria are essential organelles that convert nutrients into usable cellular energy (ATP) and perform critical roles in cell signaling, metabolism, and survival.