Biochemistry Week 7 Notes
Biochemistry Week 7 Notes BBMB 301
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This 5 page Class Notes was uploaded by Emily on Thursday February 18, 2016. The Class Notes belongs to BBMB 301 at Iowa State University taught by Robert Thornburg in Spring 2016. Since its upload, it has received 57 views. For similar materials see Survey of Biochemistry in General Science at Iowa State University.
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Date Created: 02/18/16
Biochemistry 301 Survey of Biochemistry Professor Robert Thornburg LECTURE 17 CHAPTER 17 GLUCONEOGENESIS By Emily Settle Overview of Central Metabolism o Glucose is always necessary Must be generated by an anabolic pathway if not available in diet 0 We have one day s needs of glucose stored in our bodies Once that runs out we need to make more 0 Source molecules lactate amino acids glycerol Energy input required electrons for reduction required Gycoysis vs Gluconeogenesis o Gluconeogenesis is essentially the reverse of Glycolysis Three reactions are different Gu to G6P bypass 3 F6P to FBP bypass 2 PEP to Pyruvate bypass 1 o The other seven shared rxns have AG values near 0 Reversible by changing substrate concentrations These rxns are part of both glycolysis and gluconeogenesis 0 Three unique rxns of guvoneogenesis Bypass steps of glycolysis with large negative AG Gycoysis step 1 glucose to gucose6phosphate 0 AG 79 kcalmoL Gycoysis step 3 fructose6P to fructose16BP 0 AG 53 kcalmol Gycoysis step 10 PEP to pyruvate 0 AG 41kcalmol Bypass 1 Pyruvate to Phosphoenolpyruvate 0 Two steps bypass pyruvate kinase Pyruvate carboxylase The conenzyme biotin is C02 carrier 0 ATP expended PEP carboxykinase Another ATP expended in the equivalent form of GTP Metabolites move through the mitochondria in mammals Biotin Function in Pyruvate Carboxylase 0 ATP rst forms high energy intermediate bound to C02 Mixed anhydride bond H20 C02 HCO3quot ATP l HOC02PO3quot2 ADP Ebiotin HOC02PO3quot2 l EbiotinC02 P Pyruvate EbiotinC02 l oxaloacetate Ebiotin o This is a igase reaction De nition formation of a new CC bond with the expenditure of ATP One of the six classes of reactions that occur in metabolism Hydrolase transferase isomerase oxidationreduction Hgase At this point the only one left to cover is lyase Part 2 of Bypass 1 PEP Carboxylase o Phosphoanhydride in GTP quotexchangedquot for mixed anhydride in PEP 0 Overall pyruvate has been converted to PEP 2 ATP equivalents expended Bypass 1 Movement Through Mitochondria o Oxaloacetate is not transported through the mitochondrial membranes 0 Instead oxaloacetate mitochondrial is converted into malate mitochondrial o Malate can be transported across membranes 0 Malate cytoplasm is then converted back into oxaloacetate cytoplasm 0 Result is transport of oxaloacetate from mitochondria to the cytoplasm Bypass 2 Fructose1 6BP to Fructose6P o Glycolysis step catalyzed by phosphofructose kinase Uses ATP produces ADP Irreversible because of the AG 0 Gluconeogenesis step catalyzed by fructose1 6bisphosphatase Fl 6BPase Hydrolysis reaction Bypass 3 Glucose6phosphate to Glucose 0 Similar to bypass 2 Glycolysis direction converts ATP to ADP by hexokinase Gluconeogenesis rxn hydrolyzes the phosphester bond Glucose6phosphatase a hydrolase Allosteric Regulation 0 ATP inhibits glycolysis stimulate gluconeogenesis Elevated ATP glycolysis not needed PFK pyruvate kinase inhibited Pyruvate carboxylase F1 6BPase stimulated lndirect acetylCoA and citrate elevated when ATP is elevated These positively regulate gluconeogenesis enzymes 0 ADP AMP inhibit gluconeogenesis stimulate glycolysis ATP not available for anabolism glycolysis needed to generate ATP PFK stimulated Fl 6BPase inhibited PEP carboxylase inhibited Hormonal Control 0 High blood glucose insulin released Signaling cascade activates enzyme that produces F2 6BP F2 6BP allosterically stimulates PFK Increases glycolysis F2 6BP allosterically inhibits F1 6BPase Decreases gluconeogenesis 0 Low blood glucose glucagon released Hydrolysis of F2 6BP activated level drops PFK activity decreases F1 6BPase activity increases 0 Insulin glucagon also regulate gene expression Abundance of PFK F1 6BPase reciprocally regulated Glycolysis Gluconeogenesis Occur in Different Tissues o Lactate produced from glycolysis in muscle Transported to liver 0 Gluconeogenesis in liver converts lactate to glucose ATP required 0 Glucose enters blood stream delivered to tissues Biochemistry 301 Survey of Biochemistry Professor Robert Thornburg LECTURE 18 CHAPTER 18 PYRUVATE DEHYDROGENASE COMPLEX By Emily Settle Overview of Central Metabolism 0 When 02 is available pyruvate can be further oxidized Far more ATP generated than occurs in glycolysis only Lots more NADH FADH2 generated as carbon is oxidized NADH oxidized back to NAD as 02 is reduced to H20 0 First step is the pyruvate dehydrogenase complex PDH Conversion of Glucose to C02 0 Stage 1 Glycolysis 0 Stage 2 Pyruvate Dehydrogenase Pyruvate CoASH to acetylCoA One C02 released 0 Fully oxidized carbon One NADH produced Five coenzymes used 0 Stage 3 Citric Acid Cycle AcetylCoA to 2C02 CoASH Three NADH and one FADH2 produced One GTP produced 8 enzymes cyclic reaction pathway Subject of Chapter 18 lecture 21 Pyruvate in the cytoplasm is transported into the mitochondrion where it is converted into acetylCoA in a 3 step reaction AcetylCoA is the substrate for further oxidation and production of more ATPs AcetylCoA is a fantastic energy source 0 3 different enzymes involved in this process 0 1 Pyruvate dehydrogenase o 2 Dihydrolipoyl transferase o 3 Dihydrolipoyl dehydrogenase 5 different coenzymes involved in this process 0 1 Thiamine pyrophosphate o 2 Lipoic acid 0 3 Coenzyme A o 4 FAD o 5 NAD Metabolic Features of Mitochondria 0 Two soluble spaces Intermembrane space matrix 0 Matrix PDH complex Other pathways that generate acetylCoA Citric acid cycle 0 Transporters in inner membrane Pyruvate from glycolysis in cytosol Transported to matrix Mitchondrialultrastructure 0 Huge complex 4500 kDa 24 E1 pyruvate dehydrogenase 24 E2 dihydrolipoyl transferasease 12 E3 dihydrolipoyl dehydrogenase 1 kinase 1 phosphatase 0 PDH is soluble in the matrix 0 In addition to enzymes One protein kinase and one protein phosphatase built into complex PDH Complex Reaction lll Dihydrolipoyl Transacetylase 0 High energy thioester forms Intermediate carrier is lipoamide o AcetylCoA product forms 0 The Coenzyme Lipoic Acid 0 Not derived from a vitamin Synthesized within mitochondria of mammals 0 Intermediate carrier of acyl groups Functions like coenzyme A making high energy thioester bonds 0 Forms amide linkage to lysine side chain Like biotin Bound form referred to as lipoamide PDH Complex Reaction ll Dihydrolipoyl Dehydrogenase o Dihydrolipoamide was reduced by electrons from pyruvate These are used to reduce FAD forming FADH2 Then FADH2 reduced NAD forming the product NADH Summary of PDH Reaction 0 Large negative AG Carboxylic acid oxidized to C02 Ketone is oxidized to a thioester 0 Chemical energy captured Reduce NAD to NADH NADH is high energy Chapter 19 Thioester linkage of acetylCoA Regulation of PDH o Built in protein kinase adds phosphate which inhibits PDH Occurs when ATPADP ratio is high NADHNAD ratio is high concentration of acetylCoA is high 0 Built in phosphatase removes phosphate which releases inhibition Basal activity removes inhibition if kinase not active to keep inhibition on Ca stimulates phosphatase signal from muscle activity
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