What is Kreb’s Cycle?

What is Kreb’s Cycle?

Aerobic organisms, i.e. organisms that need and use oxygen in order to live, generate energy through the Krebs cycle, also known as citric acid cycle or tricarboxylic acid cycle ( TCA cycle) and is the second stage of aerobic respiration. (stage 1: glycolysis, stage 2: TCA cyle, stage 3: Oxidative phosphorylation) The Kreb's cycle occurs in the mitochondria of eukaryotic cells, chloroplasts of plants and cytosol of bacteria. The TCA cycle is a complex series of chemical reactions during which acetate (In the form of acetyl CoA) from carbohydrates, fats and proteins is oxidized and turns into carbon dioxide . ATP, NADH and FADH (energy!) are also products of this cycle. Overall: 6 NADH's are generated (3 per Acetyl CoA that enters) 2 FADH2 is generated (1 per Acetyl CoA that enters) 2 ATP are generated (1 per Acetyl CoA that enters) 4 CO2's are released (2 per Acetyl CoA that enters) Intermediates of the cycle, such as citrate, α-ketoglutarate, succinyl CoA and oxaloacetate are used by other metabolic pathways to form cholesterol and fatty acids; glutamate, other amino acids and purines; heme, chlorophyll; aspartate, other amino acis, purines and pyrinidines respectevily. The three major affected/controlling enzymes involved in the regulation of the cycle are: citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase. Both allosteric and covalent modifications take place of enzyme regulation.