How does respiration happen in cells?

Respiration is the process which cells use to produce energy and happens in the mitochondria of the cells. Almost every cell carries out respiration. There are 4 main stages to respiration - glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation or the electron transport chain. Glycolysis converts glucose to fructose-1,6-bisphosphate which then splits to make two molecules of a three carbon compound called pyruvate. Glycolysis uses up 2 ATP but produces 4 so there is a net product of 2 ATP and 2 NADH. Pyruvate then goes into the link reaction, which is where it reacts with coenzyme A to make acetyl-CoA and gives off CO2. One molecule of NADH is also made in this process. Acetyl-CoA then goes into the Krebs cycle, which has multiple constituents and cycles through these reactions to make NADH, FADH and ATP. The NADH and FADH are the reduced counterparts of NAD and FAD, and they use this reducing potential to make ATP from ADP and phosphate using the electron transport chain in the inner mitochondrial membrane of the mitochondria.