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