The primary cellular structure responsible for energy production is the mitochondrion. Often termed the "powerhouse" of the cell, mitochondria convert nutrients into ATP (adenosine triphosphate), the cell's main energy currency, through the process of cellular respiration. This process involves aerobic respiration, which requires oxygen to oxidize glucose and produce ATP, water, and carbon dioxide. Mitochondria also play roles in the regulation of metabolic processes, apoptosis, and the generation of heat.