MCB 450 1st Edition Lecture 17 Outline of Last Lecture I Glucose can be synthesized from noncarbohydrate precursors II Gluconeogenesis and glycolysis are reciprocally regulated III The Cori cycle IV Purpose of the Pentose Phosphate Pathway PPP V Oxidative phase VI Nonoxidative phase VII Balancing the cellular needs for ATP NADPH and ribose 5 P Outline of Current Lecture I Overview of the process of complete oxidation of glucose glycolysis TCA Cycle Oxidative Phophorylation II Preparatory step for TCA Cycle Pyruvate Acetyl CoA III Reactions of the TCA Cycle 8 IV Regulation of the TCA Cycle V TCA Cycle can also provide precursors for biosynthesis VI Anaplerotic reactions VII The glycoxylate cycle Current Lecture The activation of protein kinase A by a G protein pathway Adenylate cyclase is responsible for converting ATP to cyclic AMP Insulin binds its own receptor Gluconeogenesis precursors Fatty acids cannot be used to make glucose but glycerol can Lactate comes from anaerobic glycolysis in the muscles Fate of Pyruvate under Anaerobic conditions in animals and other microorganisms lactic acid fermentation Pyruvate is a more reduced form than lactate The reaction from glucose 6 phosphate to 6 phosphoglucono alpha lactone is allosterically regulated by NADPH Isomerization Ribose 5 phosphat is a nucleic acid The nonoxidative phase includes three other reactions Don t lose any carbons they are just shuffled around This reaction is reversible These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Transketolase Both F6P and GAP are intermediates of glycolysis The NADPH and ribose 5 phosphate needs are balanced No need for the nonoxidative phase TCA Cycle Occurs in the matrix of the mitochondria 8 reactions in the TCA cycle Only other organelle that has two membranes besides the mitochondria is the nucleus The outer membrane is very permeable ATP phosphatase enzymes are embedded in the inner mitrochrondial membrane Inner membrane is not very permeable The Decisive Step Pyruvate Dehydrogenase Complex Pyruvate is made in the cytoplasm and then transported into the inner mitochondrial matrix TPP thiamine pyrophosphate Pyruvate Dehydrogenase Complex uses three catalytic coenzymes prosthetic groups Lipoic acid is the oxidized form The synthesis of acetyl CoA pyruvate consists of three steps First two steps done by E1 and third step is done by E2 Step 1 Decarboxylation E1 Carbanion of TPP Thiazole ring acts as a nucleophile Step 2 Oxidation E1 Lipoamide is bound to E2 o But will be moved to active site of E1 Slide 22 23 High energy stimulates kinase o NADH Acetyl CoA o High levels of these will turn up the kinase o NAD HS CoA ADP Pyruvate will turn off the kinase NAD Ca2 and HS CoA affects H2O to Pi o Low energy stimulates phosphotase The TCA Cycle The TCA Cycle is an amphibolic pathway Two Phases of TCA Succinyl CoA is a high energy thioester product
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