Aerobic Oxidation of Glucose Lecture Notes PDF

Aerobic Oxidation of Glucose  (Oxidative Decarboxylation of Pyruvate & Krebs' Cycle) - After the conversion of glucose into two moles of pyruvate through the cytoplasmic steps of glycolysis, pyruvate is oxidatively decarboxylated into Acetyl-CoA in the mitocho...

Aerobic Oxidation of Glucose  (Oxidative Decarboxylation of Pyruvate & Krebs' Cycle) - After the conversion of glucose into two moles of pyruvate through the cytoplasmic steps of glycolysis, pyruvate is oxidatively decarboxylated into Acetyl-CoA in the mitochondria by the pyruvate dehydrogenase enzyme complex.  Steps: - It is a preparatory phase for Krebs' cycle. Pyruvate passes into the mitochondria by the help of a special transporter on inner mitochondrial membrane. - Oxidative decarboxylation is removal of hydrogen & CO2 from pyruvate to give acetyl-CoA and produce NADHH - NADHH give 2.5 ATP - 2 NADHH per one glucose ,,,,,,,2*2.5=5 ATP in the preparatory phase -catalyzed by an enzyme complex called pyruvate dehydrogenase Pyruvate dehydrogenase utilizes 5 coenzymes 1-Thiamin pyrophosphate (TPP), 2- Coenzyme A (CoASH), 3-Lipoic acid 4-Flavin adenine dinucleotide (FAD), 5- Nicotinamide adenine dinucleotide (NAD) COOH Pyruvate O C O Dehydrogenase H3C C ~ SCoA FAD S Active acetate CH3 L TPP S (Acetyl-CoA) Pyruvate CoASH NADH.H+ NAD CO2 Regulation of Pyruvate dehydrogenase:  Krebs' cycle (Or, Citric Acid cycle, or, Tricarboxylic acid cycle) Definition : - It is the cycle by which active acetate (acetyl-CoA) produced from pyruvate, ketogenic amino acids or oxidation of fatty acids is completely oxidized into CO2, FADH2, and NADH.H+. Hydrogen of these coenzymes is converted into H2O by the respiratory chain, Thus, Krebs' cycle is a common pathway for oxidation of all nutrients (carbohydrate, lipids and proteins).  Biological importance of Krebs' cycle: 1-Oxidation of acetyl-CoA formed from carbohydrates (as pyruvate), fat, and ketogenic amino acids into CO2 + H2O with generation of energy. Acetyl COA oxidation in TCA cycle produce:3NADHH,1FADH2 ,&1ATP directly by substrate level phosphorylation Glucose produce 5 or 7 ATP IN glycolysis+5ATP IN oxidative decarboxylation of pyruvate+20 ATP IN TCAcycle =30 or 32 ATP totally in aerobic condtion 2-It is a major source of succinyl-CoA which is used for: Synthesis of hemoglobin and other porphyrins. 3-It provides intermediates for synthesis of non-essential amino acids, e.g.,: -Ketoglutarate can give rise to glutamic acid by transamination. Oxaloacetate can give rise to asparatic acid by transamination.  Choose the best single answer: 1- pyruvate is oxidatively decarboxylated into : a) Acetyl-CoA b) oxaloacetate c) citrate d) lactate 2-Pyruvate dehydrogenase utilizes all the following coenzymes except: a) TPP b) Lipoic acid c) PLP d) NAD The key regulatory enzyme are stimulated by: 1-acetyl coA 2-ADP Inhibited by ATP  In vitro inhibitors of Krebs' cycle: 1. Fluoroacetate: Inhibits aconitase enzyme. 2. Arsenate: -ketoglutarate dehydrogenases. 3. Malonate : Inhibits succinate dehydrogenase enzyme  Choose the best single answer: 1-The key regulatory enzyme of TCA are stimulated by a) ATP b) acetyl coA c) malonate d) oxaloacetate 2- Fluoroacetate inhibit: a) aconitase b) citrate synthase c) hexokinase d) fumarase