Metabolism of Carbohydrates: Glycolysis and Gluconeogenesis , Citric Acid Cycle [Tricarboxylic acid (TCA) cycle] [Krebs cycle]
Pyruvate Dehydrogenase Links Glycolysis to the Citric Acid Cycle
The Citric Acid Cycle Oxidizes Two-Carbon Units
Entry to the Citric Acid Cycle and Metabolism Through It Are Controlled
The Citric Acid Cycle Is a Source of Biosynthetic Precursors
The citric acid cycle is the final common pathway for the oxidation of fuel molecules.
Most fuel molecules enter the cycle as acetyl coenzyme A.
The function of the citric acid cycle is the harvesting of high energy electrons from carbon fuels.
The citric acid cycle itself neither generates a large amount of ATP nor includes oxygen as a reactant.
Overview of glucose aerobic oxidation
The citric acid cycle constitutes the first stage in cellular respiration, the removal of high-energy electrons from carbon fuels in the form of NADH and FADH2 (left).
These electrons reduce O2 to generate a proton gradient (red pathway),
which is used to synthesize ATP (green pathway). The reduction of O2 and the synthesis of ATP constitute oxidative phosphorylation.
Pyruvate Dehydrogenase links gly to tca
Pyruvate Dehydrogenase complex
Pyruvate dehydrogenase component
Oxidative decarboxylation of pyruvate
Transfer of acetyl group to CoA
Regeneration of the oxidized form of lipoamide
1-Carbanion of TPP Carbanion of TPP + Pyruvate -> Hydroxyethyl-TPP
1-Hydroxyethyl-TPP + Lipoamide -> Carbanion of TPP + Acetyllipoamide(high energy)
2-Coenzyme A+Acetyllipoamide -> Acetyl CoA(high energy)+Dihydrolipoamide