Aerobic respiration requires the presence of oxygen to produce large amounts of ATP from pyruvate. Respiration is an exothermic catabolic process, where larger units of energy at broken into smaller units for cell utilization, and additionally the process releases heat. There are three main processes in aerobic respiration: glycolysis, Krebs cycle and oxidative phosphorylation (electron flow).
Glycolysis occurs in both aerobic and anaerobic respiration, and it is when one molecule of glucose is converted to 2 units of pyruvate. There are two stages in Glycolysis called the ‘Preparatory Phase’, where 2 ATP is consumed, and ‘Pay Off Phase’ where 4 ATP units are produced – net gain of 2 ATP. The Krebs cycle occurs in the mitochondrial matrix where Acetyl-CoA is generated from the pyruvate, this molecule helps form citrate in the Citric Acid Cycle. Oxygen presence becomes integral in Oxidative Phosphorylation, this is where products from the Krebs cycle, namely NADH and FADH2 are reduced to produce electrons that are fed into the Electron Transport Chain (ETC). The electrons move downhill, by using the electrochemical proton gradient. In total, 38 ATP are produced.