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1
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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4
3.blood sugar
• the sources & outlet
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Blood glucoseLiver glycogen
Dietary carbohydrate
Glucogenesis (A.A,lactate,etc)
Liver ,muscle glycogen
Catabolism (H20,CO2,ATP)
Other substrates
glycosuria
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• blood sugar concentration is
regulated by tissues,hormones
Decreasing blood sugar level:
hormone insulin
7
elevating blood sugar level:
hormone
Glucagon,epinephrine,glucocorticoid, growth hormone
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Blood glucoseLiver glycogen
Dietary carbohydrate
Glucogenesis (A.A,lactate,etc)
Liver ,muscle glycogen
Catabolism (H20,CO2,ATP)
Other substrates
glycosuria
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Hyperglycosemia: >7.2mmol/L
Hypoglycosemia: <3.9mmol/L
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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
carbohydrates
anaerobic glycolysis
Aerobic
oxidationpentose 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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F6P FBP
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• the characteristics of
HK,PFK
• the changes of the energy
• the significance
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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
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名称 己糖激酶 葡萄糖激酶
存在 各组织细胞 肝细胞
底物 G G
产物 G6P G6P
Km 0.01-0.1mM 10-20mM
抑制剂 G6P ——
高糖膳食后,肝中的 G G6P Gn 储存
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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
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2) Formation of glyceraldehyde-3-
phosphate (G3P) by cleavage and
isomerization
DAP
DAPG3P
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3) Formation of pyruvate
a. dehydrogenation
G3P
BPG
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b. energy released
BPG 3PG
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c. transfer phosphoryl group
3PG 2PG
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d. dehydrate
2PG PEP
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e. energy released
PEP
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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 glycolysis
reaction ATP change per glucose
G-----------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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LDH
CH3 - C- COOH CH3-CH-COOH
O OH
+ + NADH+H+ NAD+
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B. Aerobic oxidation of glucose
• general
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lactate pyruvate 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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1) 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+ FADH2 ATP GTP CO2 H2O
Formation of pyruvate
2 ( 1 ) 2 或 3
2 ( 1)
2 ( 1 )
acetyl
CoA enter TCA cycle
2 ( 1 ) 2 ( 1
)
2 ( 1)
2 ( 1)
2 ( 1 ) 2 ( 1 )
2 ( 1 )
2 ( 1 )
2 ( 1 )
formation of acetyl CoA
2(1)
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Glucose+6O2 6CO2+6H2O = -2790kJ/mol
30.5KJ38/2790KJ=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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C3
C7
C6
C4
C3
C6
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• 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)
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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
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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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★ 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
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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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F.The control of glycogenolysis
& glycogenesis
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G. gluconeogenesis
• concept
• the reaction site
• basic process
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HK PFK
G G6P G6F 1 , 6 2P-F(FBP)
3 PG BPG G3P
PK
PEP pyruvate
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ADP HK ATP
① G-6-P G
glucose-6-phosphatase
ADP PFK ATP
② 1 , 6-2P-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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a.In a long period of
starvation
b.Reuse of lactate: cori’s
cycle
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c. Promote the excretion
of H+ in kidney
# lactic acidosis
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H+ PEP carboxykinase
0xaloacetate PEP Oxaloacetate , α-ketoglutarate oxatoacetate
α-ketoglutarate , Glu
NH3 NH3+H+ NH4 ( excrete ) Gln
100
• gluconeogenesis &
glycolysis are reciprocally
regulated