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

Hyperglycosemia: >7.2mmol/LHypoglycosemia:

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

(32)

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