Metabolism of   carbohydrates
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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.

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Metabolism of carbohydrates

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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 (H20,CO2,ATP)

Dietary carbohydrate

Liver ,muscle glycogen

Liver glycogen

Blood glucose

Other substrates

Glucogenesis (A.A,lactate,etc)

glycosuria


• blood sugar concentration is

regulated by tissues,hormones

Decreasing blood sugar level:

hormone insulin


elevating blood sugar level:

hormone

Glucagon,epinephrine,glucocorticoid, growth hormone


Catabolism (H20,CO2,ATP)

Dietary carbohydrate

Liver ,muscle glycogen

Liver glycogen

Blood glucose

Other substrates

Glucogenesis (A.A,lactate,etc)

glycosuria


Hyperglycosemia: >7.2mmol/L

Hypoglycosemia: <3.9mmol/L


• The tolerance to carbohydrates

Tolerance test for glucose


4. the catabolic pathway of

carbohydrates


catabolic pathway of

carbohydrates

Aerobic

oxidation

anaerobic glycolysis

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

G6P

G


F6P

G6P


FBP

F6P


• the characteristics of

HK,PFK

• the changes of the energy

• the significance


己糖激酶(HK)

a 二亚基的变构酶

b 催化不可逆反应,关键酶

ΔGo = -4.5 Kcal/mol

c 葡萄糖激酶是肝中存在的己糖激酶的同工酶


高糖膳食后,肝中的 G G6P Gn 储存


磷酸果糖激酶(PFK)

a 四亚基的变构酶

b 催化不可逆反应 关键酶

ΔGo = -3.4 Kcal/mol

c 酵解过程中的主要限速酶

★、 磷酸化酶 (phosphorylase)

a 催化反应, α-1,4 糖苷键

磷酸解

b 产物 G1P Gn-1


2) Formation of glyceraldehyde-3-

phosphate (G3P) by cleavage and

isomerization

DAP

G3P

DAP


3) Formation of pyruvate

a. dehydrogenation

BPG

G3P


b. energy released

BPG

3PG


c. transfer phosphoryl group

2PG

3PG


d. dehydrate

2PG

PEP


e. energy released

PEP


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 glycolysis

ATP change per glucose

reaction

- 1

G-----------G6P

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 glycolysis

a. enzymes

b. hormones

c. ATP/ADP


LDH

CH3 - C- COOH CH3-CH-COOH

O OH

+ +

NADH+H+ NAD+


B. Aerobic oxidation of glucose

• general


lack of O2

O2

lactate

pyruvate

acetyl CoA

Citric acid cycle

Biological oxidation

CO2,H2O, energy


• 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+

FADH2

ATP

GTP

CO2

H2O

Formation of pyruvate

2(1)

2或3

2(1)

2(1)

formation of acetyl CoA

acetyl

CoA enter TCA cycle

2(1)

2(1)

2(1)

2(1)

2(1)

2(1)

2(1)

2(1)

2(1)

2(1)


Glucose+6O2 6CO2+6H2O = -2790kJ/mol

30.5KJ38/2790KJ=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


C3

C6

C4

C7

C3

C6


• Physiologic role of Pentose

phosphate pathway

a.providing NADPH+H+ for biosyntheses

b.Providing ribose 5-phosphate for nucleotide

lack of G6PDH (erythrocyte hemolytic

anemia)


五、生理意义

①非供能,提供生物合成所需的原料

a、5-P核糖

b、还原型NADPH

⑴ 合成FA,类固醇激素,胆固醇

⑵ 维持体内一定量的GSH,保持RBC的完整性,保护SH酶的活性


NADPH+H+ NADP+

G-S-S-G GSH

(oxidation) (deoxidized)

peroxides FA(unsaturated )

lysosome hydrolase

release

cell membrane hemolysis


★ 遗传性GPDH缺乏症 蚕豆黄

c、加单氧酶体系供氢体

参与生物转化

d、WBC的杀菌作用,过氧化氢的

生成

2、3C,4C,5C,6C,7C糖的互变


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


HKPFK

G G6P G6F 1,6 2P-F(FBP)

3 PG BPG G3P

PK

PEP pyruvate


ADP HK ATP

① G-6-P G

glucose-6-phosphatase

ADP PFK ATP

② 1,6-2P-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

  • starvation

  • Reuse of lactate: cori’s

  • cycle


  • Promote the excretion

  • of H+ in kidney

  • # lactic acidosis


H+ PEP carboxykinase

0xaloacetate PEP

Oxaloacetate , α-ketoglutarate oxatoacetate

α-ketoglutarate,

Glu

NH3 NH3+H+ NH4(excrete)

Gln


• gluconeogenesis &

glycolysis are reciprocally

regulated


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