The Krebs cycle, otherwise known as the citric acid cycle, is named after Hans Krebs who worked out this cyclic process. A major phase of cellular respiration, the Krebs cycle occurs in the mitochondria of animal and plant cells (as in the organism shown above). It starts with acetyl CoA being split up and converted into citrate. Then, successive redox reactions generate NADH, ATP, and CO2, as well as FADH2 and NADH. Electrons are also released in order to power oxidative phosphorylation, the next phase of cellular respiration.