metabolism of carbohydrates
DESCRIPTION
Metabolism of carbohydrates. 1. summarize. 2. Digestion & absorption. • Hydrolyzed by enzyme. • Final products - glucose. • active absorptive process at small intestine. 3.blood sugar. • the sources & outlet. Catabolism (H 2 0,CO 2 ,ATP). Dietary carbohydrate. - PowerPoint PPT PresentationTRANSCRIPT
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Metabolism of carbohydrates 1. summarize
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2. Digestion & absorption Hydrolyzed by enzyme active absorptive process at small intestine Final products - glucose
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3.blood sugar the sources & outlet
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Blood glucoseLiver glycogenDietary carbohydrateGlucogenesis (A.A,lactate,etc)Liver ,muscle glycogenCatabolism (H20,CO2,ATP) Other substrates glycosuria
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blood sugar concentration is regulated by tissues,hormonesDecreasing blood sugar level: hormone insulin
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elevating blood sugar level: hormoneGlucagon,epinephrine,glucocorticoid, growth hormone
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Blood glucoseLiver glycogenDietary carbohydrateGlucogenesis (A.A,lactate,etc)Liver ,muscle glycogenCatabolism (H20,CO2,ATP) Other substrates glycosuria
- Hyperglycosemia: >7.2mmol/LHypoglycosemia:
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The tolerance to carbohydrates Tolerance test for glucose
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4. the catabolic pathway of carbohydrates
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catabolic pathway of carbohydratesanaerobic glycolysisAerobicoxidation
pentose pathway
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A. Anaerobic glycolysis concept Glycolysis is the sequence of reactions that converts glucose into lactate with the concomitant production of ATP,under anaerobic conditions
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the reaction site: cytosol basic process (4 phases)
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1) phosphorylation of hexoses GG6P
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G6PF6P
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F6PFBP
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the characteristics of HK,PFK the changes of the energy the significance
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HK a b Go = -4.5 Kcal/mol c
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G G6P Gn
GGG6PG6PKm0.01-0.1mM10-20mMG6P
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PFK a b Go = -3.4 Kcal/mol c phosphorylase a -1,4 b G1P Gn-1
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2) Formation of glyceraldehyde-3- phosphate (G3P) by cleavage and isomerizationDAPDAPG3P
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3) Formation of pyruvatea. dehydrogenationG3PBPG
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b. energy releasedBPG3PG
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c. transfer phosphoryl group3PG2PG
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d. dehydrate2PGPEP
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e. energy releasedPEP
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4) reduction of pyruvate to lactate
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summarize a. concept b. the reaction site c. basic process (4 phases) d.key enzyme,limited enzyme e. the changes of energy
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Consumption & generation of ATP in glycolysisreactionATP change per glucoseG-----------G6P - 1 F6P--------FBP -1(2) BPG----(2) 3PG +2(2)PEP-------(2)pyruvate +2 net +2
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f. characteristics g. Physiologic role of glycolysis the control of glycolysisa. enzymes b. hormones c. ATP/ADP
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LDHCH3 - C- COOH CH3-CH-COOH O OH + + NADH+H+ NAD+
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B. Aerobic oxidation of glucose general
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lactatepyruvate acetyl CoA Citric acid cycle Biological oxidation CO2,H2O, energy O2 lack of O2
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the reaction site basic process (3 phases)
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glycolysis (G----------pyruvate) 2) formation of acetylCoA from pyruvate
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Components of pyruvate dehydrogenase complex
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3) Citric acid cycle a. acetyl CoA entering Citric acid cycle(synthesis of citric acid )
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b. dehydrogenation & decarboxylation
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In this stage produced: 2 molecules of CO2 2 pairs of NADH+H+ 1 molecule of GTP
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c. Regenesis of oxaloacetate
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the sources of oxaloacetate
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In this stage produced: 1 pairs of FADH2 1 pairs of NADH+H+
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summarize a. concept b. the reaction site c. basic process (3 phases)d. key enzyme e. the changes of energy
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(32)
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NADH+H+FADH2ATPGTPCO2H2OFormation of pyruvate21232121acetyl CoA enter TCA cycle21 212121 21 21212121 formation of acetyl CoA2(1)
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Glucose+6O2 6CO2+6H2O = -2790kJ/mol30.5KJ38/2790KJ=41%
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f. characteristics
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g. Physiologic role of aerobic oxidation of glucose & TCA cycle
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the control of aerobic oxidation of glucose & TCA cycle Pasteur effect crabtree effect
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a. enzymes b. hormones c. ATP/ADP
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C .Pentose phosphate pathway(hexose monophosphate shunt) general the reaction site
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basic process (2 phases)a. Oxidation stage
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b. non oxidation stage
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C3C7C6C4C3C6
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Physiologic role of Pentose phosphate pathway a.providing NADPH+H+ for biosynthesesb.Providing ribose 5-phosphate for nucleotide lack of G6PDH (erythrocyte hemolytic anemia)
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a5-P bNADPH FA GSHRBCSH
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NADPH+H+ NADP+ G-S-S-G GSH oxidation deoxidized
peroxides FA(unsaturated )
lysosome hydrolase release cell membrane hemolysis
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GPDH c dWBC 23C4C5C6C7C
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D. glycogenolysis concept the reaction site basic process
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E. glycogenesis concept the reaction site basic process
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The control of glycogenolysis & glycogenesis
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G. gluconeogenesis concept the reaction site basic process
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HK PFKG G6P G6F 16 2P-F(FBP) 3 PG BPG G3P PK PEP pyruvate
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ADP HK ATP
G-6-P G glucose-6-phosphatase ADP PFK ATP
16-2P-F G6F fructose I,6-biphosphatase
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3. Phosphoenelpyruvate is formed from pyruvate by way of oxaloacetate (bypass of carboxylation of pyruvate) Key enzyme: pyruvate carboxylase PEP carboxykinase
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the key enzyme Physiologic role of gluconeogenesis
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In a long period of starvationReuse of lactate: coris cycle
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Promote the excretion of H+ in kidney lactic acidosis
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H+ PEP carboxykinase
0xaloacetate PEP Oxaloacetate -ketoglutarate oxatoacetate-ketoglutarate Glu NH3 NH3+H+ NH4excrete Gln
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gluconeogenesis & glycolysis are reciprocally regulated