 In this video I will describe how the fate of pyruvate depends on oxygen availability. Following glycolysis, pyruvate can either continue through aerobic cellular respiration or anaerobic cellular respiration depending upon the presence of oxygen. If sufficient oxygen is available and the cell contains mitochondria, then pyruvate can enter the pyruvate dehydrogenase complex within the mitochondria. Following the pyruvate dehydrogenase complex, acetylcoenzyme A will enter into the citric acid cycle and then the citric acid cycle will convert all of the carbon from glucose into carbon dioxide molecules and the electrons from glucose, from pyruvate and from acetyl coa are transferred into oxidative phosphorylation by electron carriers NADH and FADH2. During oxidative phosphorylation, oxygen is required to enable the electron transport chain to oxidize NADH and FADH2 as oxygen will be reduced producing water. However, if there is not sufficient oxygen available to run aerobic cellular respiration or the cell does not contain mitochondria, ATP can be generated with anaerobic cellular respiration where pyruvate will enter into lactic acid fermentation. Lactic acid fermentation will reduce pyruvate to form lactate or lactic acid. Lactic acid and lactate are the conjugate acid base pair so they're easily interconvertible. The hydrogene electrons required for the reduction of pyruvate forming lactate come from NADH and this NADH is generated by glycolysis. Lactic acid fermentation enables the regeneration of NAD plus that is required to maintain glycolysis by running anaerobic cellular respiration. Two molecules of ATP are produced from every molecule of glucose. Each molecule of glucose is converted to two molecules of lactate and the energy that's released is stored in two molecules of ATP.