Cellular respiration is a process in which cellular energy is generated through the oxidation of nutrient molecules, with oxygen as the ultimate electron acceptor.
Stages of cellular respiration
There are two stages of cellular respiration. In stage I, pyruvate is converted to acetyl CoA with the help of pyruvate dehydrogenase complex by oxidative Decarboxylation. Coenzyme A activates acetyl group derived from pyruvate. In stage II, acetyl CoA enters the TCA cycle and gets oxidized through 8 steps, generating ATPs.
The Citric acid cycle
TCA cycle is a cyclic pathway and the subcellular site of the reaction is mitochondria in eukaryotes. Formation of citrate, then, isocitrate, oxidation of isocitrate, oxidation of α ketoglutarate, conversion of succinyl CoA to succinate, oxidation of succinate, hydration of fumarate, oxidation of malate to oxaloacetate. They are the 8 steps of TCA cycle. Net ATP gain from one glucose molecule is 38.
Phases of reactions of citric acid cycle
Amphibolic pathway is the metabolic pathway used in both catabolism and anabolism. TCA cycle acts as an amphibolic pathway since it is involved in both breakdown as well as synthesis of biomolecules. There are Anaplerotic reactions which replenish the supply of intermediates in the citric acid cycle. Ex: Malate is formed from pyruvate by the malic enzyme.