Metabolism of carbohydrates
1. summarize
1
2. Digestion & absorption
• Hydrolyzed by enzyme
• Final products - glucose
• active absorptive process
at small intestine
2
3
3.blood sugar
• the sources & outlet
4
Catabolism
(H20,CO2,ATP)
Dietary carbohydrate
Liver glycogen
Blood glucose
Liver ,muscle
glycogen
Other
substrates
Glucogenesis
(A.A,lactate,etc)
glycosuria
5
• blood sugar concentration is
regulated by tissues,hormones
Decreasing blood sugar level:
hormone
insulin
6
elevating blood sugar level:
hormone
Glucagon,epinephrine,glucocort
icoid, growth hormone
7
Catabolism
(H20,CO2,ATP)
Dietary carbohydrate
Liver glycogen
Blood glucose
Liver ,muscle
glycogen
Other
substrates
Glucogenesis
(A.A,lactate,etc)
glycosuria
8
Hyperglycosemia:
Hypoglycosemia:
>7.2mmol/L
<3.9mmol/L
9
• The tolerance to carbohydrates
Tolerance test for glucose
10
11
4. the catabolic pathway of
carbohydrates
12
catabolic pathway of
carbohydrates
anaerobic
glycolysis
Aerobic
oxidation
pentose
pathway
13
A. Anaerobic glycolysis
• concept
Glycolysis is the sequence of
reactions that converts glucose
into lactate with the concomitant
production of ATP,under
anaerobic conditions
14
• the reaction site: cytosol
• basic process
(4 phases)
15
1) phosphorylation of hexoses
G
G6P
16
G6P
F6P
17
F6P
FBP
18
• the characteristics of
HK,PFK
• the changes of the energy
• the significance
19
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
20
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
21
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
22
2) Formation of glyceraldehyde-3phosphate (G3P) by cleavage and
isomerization
DAP
G3P
DAP
23
3) Formation of pyruvate
a. dehydrogenation
BPG
G3P
24
b. energy released
BPG
3PG
25
c. transfer phosphoryl group
3PG
2PG
26
d. dehydrate
2PG
PEP
27
e. energy released
PEP
28
4) reduction of pyruvate to
lactate
29
• summarize
a. concept
b. the reaction site
c. basic process (4 phases)
d.key enzyme,limited enzyme
e. the changes of energy
30
Consumption & generation of ATP
in glycolysis
reaction
ATP change per glucose
G-----------G6P
-1
F6P--------FBP
-1
(2) BPG----(2) 3PG
(2)PEP-------(2)pyruvate
+2
+2
net +2
31
f. characteristics
g. Physiologic role of glycolysis
• the control of glycolysis
a. enzymes
b. hormones
c. ATP/ADP
32
33
34
LDH
CH3 - C- COOH
O
+
NADH+H+
CH3-CH-COOH
OH
+
NAD+
35
B. Aerobic oxidation of glucose
• general
36
lack of O2
lactate
pyruvate
O2
acetyl CoA
Citric acid cycle
Biological oxidation
CO2,H2O, energy
37
• the reaction site
• basic process
(3 phases)
38
1) glycolysis
(G----------pyruvate)
2) formation of acetylCoA
from pyruvate
39
40
• Components of pyruvate dehydrogenase
complex
41
42
43
3) Citric acid cycle
a. acetyl CoA entering Citric
acid cycle
(synthesis of citric acid )
44
45
b. dehydrogenation & decarboxylation
46
47
48
49
• In this stage produced:
2 molecules of CO2
2 pairs of NADH+H+
1 molecule of GTP
50
c. Regenesis of oxaloacetate
51
52
53
• the sources of oxaloacetate
54
• In this stage produced:
1 pairs of FADH2
1 pairs of NADH+H+
55
• summarize
a. concept
b.
c.
the reaction site
basic process (3 phases)
d.
key enzyme
e. the changes of energy
56
57
(32)
58
NADH+H+
Formation of
pyruvate
formation of
acetyl CoA
FADH2
2（1）
ATP
GTP
CO2
2或3
2（1）
2（1）
acetyl
2（1）
CoA enter
TCA cycle
2（1）
H2O
2（1） 2（1）
2（1） 2（1）
2（1）
2(1)
2（1）
2（1）
59
Glucose+6O2
6CO2+6H2O = -2790kJ/mol
30.5KJ38/2790KJ=41%
60
f. characteristics
61
62
g. Physiologic role of aerobic
oxidation of glucose & TCA
cycle
63
64
• the control of aerobic
oxidation of glucose & TCA
cycle
Pasteur effect
crabtree effect
65
a. enzymes
b. hormones
c. ATP/ADP
66
C .Pentose phosphate pathway
(hexose monophosphate shunt)
• general
• the reaction site
67
• basic process
(2 phases)
a. Oxidation stage
68
69
b. non oxidation stage
70
C3
C6
C4
C7
C3
C6
71
• 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)
72
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
73
NADPH+H+
NADP+
G-S-S-G
（oxidation）
GSH
（deoxidized）
peroxides
lysosome
FA(unsaturated )
hydrolase
release
cell membrane
hemolysis
74
★ 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
75
D. glycogenolysis
• concept
• the reaction site
• basic process
76
77
78
79
E. glycogenesis
• concept
• the reaction site
• basic process
80
81
82
83
84
F.The control of glycogenolysis
& glycogenesis
85
86
87
G. gluconeogenesis
• concept
• the reaction site
• basic process
88
89
HK
G
PFK
G6P
G6F
3 PG
1，6 2P-F(FBP)
BPG
G3P
PK
PEP
pyruvate
90
ADP HK ATP
① G-6-P
G
glucose-6-phosphatase
ADP PFK ATP
② 1，6-2P-F
G6F
fructose I,6-biphosphatase
91
3. Phosphoenelpyruvate is formed from
pyruvate by way of oxaloacetate
(bypass of carboxylation of pyruvate)
Key enzyme:
pyruvate carboxylase
PEP carboxykinase
92
93
94
• the key enzyme
• Physiologic role of
gluconeogenesis
95
a.In a long period of
starvation
b.Reuse of lactate: cori’s
cycle
96
97
c. Promote the excretion
of H+ in kidney
＃ lactic acidosis
98
H+
PEP
carboxykinase
0xaloacetate
PEP
Oxaloacetate ， α-ketoglutarate
oxatoacetate
α-ketoglutarate ，
Glu
NH3
NH3+H+
NH4（excrete）
Gln
99
• gluconeogenesis &
glycolysis are reciprocally
regulated
100