The Citric Acid cycle Pyruvate to Acetyl CoA Pyruvate and acetyl-CoA used for energy AND to synthesize amino acids and lipids etc Mitochondria
Pyruvate in cytoplasm
Enters mitochondria
Pyruvate dehydrogenase is in matrix Pyruvate Dehydrogenase
Huge complex (50nm) (ribosome is 5nm)
Three sub-complexes- E1, E2 and E3 Commits pyruvate to AcCoA formation Pyruvate dehydrogenase Pyruvate to Acetyl CoA
The reaction Ist step intermediate
2nd step intermediate 3rd step intermediate 4th step
Reactions in the complex
Co-ordinated substrate channeling-pass substrate form 1 active site to next Fast reaction, minimized side reaction, co-ordinated process, high substrate conc Oxidative decarboxylation of pyruvate Regulation of PDH
Increased AcCoA inhibits E2 in PDH (monitors amt of energy). High AcCoA, switch off respiration, use pyruvate to switch on gluconeogenesis (formation of glycogen etc) xxxxxxx Citric Acid cycle
2C + 4C ------> 6C -----> CO2 + 4C
16 electrons The overall reaction
Step1 Oxaloacetate and acetylCoA bind enzyme in open state. Enzyme changes shape, brings the reactants together and condensation occurs
Step2
Step3 Step4 Step5 Cleavage of thiol energy bond and release of CoA is coupled to formation of GTP PO4 nucleophilic attack on succinate His cleaves PO4 off of succinate. PO4 transfers from His(enzyme) to GDP forming GTP Details
Cleavage of thiol energy bond and release of CoA is coupled to formation of GTP PO4 nucleophilic attack on succinyl CoA releasing CoA. His cleaves PO4 off of succinate. PO4 transfers from His(enzyme) to GDP forming GTP
Oxidation Hydroxylation
Step6-8 Step6
Succinate dehydrogenase- uses FAD and generates FADH2. This enzyme is not in matrix but in inner mitochondrial membrane and hands FADH2 directly to the electron transport system
Step7
Step8
Citric acid cycle and Anabolism
Role of the citric acid cycle in anabolism. Intermediates of the citric acid cycle are drawn off as precursors in many biosynthetic pathways. Shown in red are four anaplerotic reactions that replenish depleted cycle intermediates The cycle and Anabolism Regulatory steps Regulation Glyoxylate cycle
Glyoxylate and Citric acid cycle