1. CARBOHYDRATE METABOLISM
بايو كمستري (م 2) / د . احمد الطويل
ثاني اسنان موصل
23 / 11 / 2015
CARBOHYDRATE METABOLISM
Dr. Ahmed Al Taweel

2. CARBOHYDRATE DIGESTION
AMYLUM digestion by amylase enzyme

3. Disaccharides digestion

4. Glucose is the most important carbohydrate
Glucose is the major metabolic fuel of mammals, except ruminants
Monosaccharide from diet :
- Glucose
- Fructose
- Galactose
Fructose and Galactose glucose at the liver

5. Galactose Metabolism

6. Fructose Metabolism

7. Blood glucose carbohydrate metabolism exist are :
1. Glycolisis
2. Glycogenesis
3. HMP Shunt
4. Oxidation of Pyruvate
5. Kreb’s Cycle
6. Change to lipids
Fasting blood glucose carbohydrate metabolism :
1. Glycogenolisis
2. Gluconeogenesis

8. GLYCOLISIS Glycolisis oxidation of glucose energy
It can function either aerobically or anaerobically
pyruvate lactate
Occurs in the cytosol of all cell
AEROBICALLY GLYCOLYSIS :
Pyruvate Mitochondria oxidized to Asetil CoA Kreb’s Cycle
CO2 + H2O + ATP

9. Glycolisis

10. Most of the reaction of glycolysis are reversible, except of three reaction :
1. Glucose Glucose-6-phosphate, catalyzed by Hexokinase / Glucokinase
Hexokinase :
- Inhibited allosterically by its product glucose-6-p
- Has a high affinity for its substrate glucose
- available at all cell, except liver and islet cell

11. Glucokinase :
- available at liver and islet cell
- in the liver to remove glucose from the blood after meal
2. Fructose-6-P Fructose-1,6-biP
- catalyzed by Phosphofructokinase enzyme
- Irreversible
- Rate limiting enzyme in glycolysis
3. Phosphoenolpyruvate Enol Pyruvate
- Catalyzed by Pyruvate kinase enzyme
Oxidation of 1 mol glucose mol ATP and 2 mol Pyruvate

12. ANAEROBICALLY GLYCOLYSIS :
- The reoxidation of NADH through the respiratory chain to oxygen is prevented
- Pyruvate is reduced by the NADH to lactate, by Lactate dehidrogenase enzyme
Lactate dehydrogenase
Pyruvate + NADH + H Lactate + NAD+
- Oxidation 1 mol glucose via anaerobically glycolysis mol ATP

13. ANAEROBICALLY GLYCOLYSIS :
Respiratory chain is absence
Reoxidation of NADH NAD+ via Respiratory chain is inhibited
Reoxidation of NADH via lactate formation allows glycolysis to proceed in the absence of oxygen by regenerating sufficient NAD+

14. GLYCOLYSIS IN ERYTHROCYTE
Erythrocyte lack mitochondria respiratory chain and Kreb’s cycle are absence
Always terminates in lactate
In mammals the reaction catalyzed by phosphoglycerate kinase may be bypassed by a process that catalyzed Biphosphoglycerate muta- se
Its does serve to provide 2,3-biphosphoglycerate
bind to hemoglobin decreasing its affinity for oxygen oxygen readily available to tissues

15. GLYCOLYSIS IN ERYTHROCYTE

16. OXIDATION OF PYRUVATE Occur in mitochondria
Oxidation of 1 mol Pyruvate mol Asetyl-CoA + 3 mol ATP
CH3COCOOH + HSCoA + NAD CH3CO-SCoA + NADH
(Pyruvate) (Asetyl-CoA)
Catalyzed by Pyruvate dehydrogenase enzyme
This enzyme need CoA as coenzyme
In Thiamin deficiency, oxydation of pyruvate is impaired lactic and pyruvic acid

17. GLYCOGENESIS Synthesis of Glycogen from glucose
Occurs mainly in muscle and liver cell
The reaction :
Glucose Glucose-6-P
Hexokinase / Glucokinase
Glucose-6-P Glucose-1-P
Phosphoglucomutase
Glucose-1-P + UTP UDPG + Pyrophosphate
UDPG Pyrophosphorylase

18. GLYCOGENESIS
Glycogen synthase catalyzes the formation of α-1,4-glucosidic linkage in glycogen
Branching enzyme catalyzes the formation of α-1,6-glucosidic linkage in glycogen
Finally the branches grow by further additions of 1 → 4-gucosyl units and further branching (like tree!)

19. SYNTHESIS OF GLYCOGEN

20. SYNTHESIS OF GLYCOGEN

21. GLYCOGENESIS AND GLYCOGENOLYSIS PATHWAY

22. Glycogenesis Glycogenolysis

23. GLYCOGENOLYSIS The breakdown of glycogen
Glycogen phosphorilase catalyzes cleavage of the 1→4 linkages of glycogen to yield glucose-1-phosphate
α(1→4)→α(1→4) glucan transferase transfer a trisaccharides unit from one branch to the other
Debranching enzyme hydrolysis of the 1→6 linkages
The combined action of these enzyme leads to the complete breakdown of glycogen.

24. GLYCOGENOLYSIS Phosphoglucomutase Glucose-1-P Glucose-6-P
Glucose-6-phosphatase
Glucose-6-P Glucose
Glucose-6-phosphatase enzyme a spesific enzyme in liver and kidney, but not in muscle
Glycogenolysis in liver yielding glucose export to blood to increase the blood glu-
cose concentration
In muscle glucose-6-P glycolysis

25. GLUCONEOGENESIS
Pathways that responsible for converting noncarbohydrate precursors to glucose or glycogen
In mammals occurs in liver and kidney
Major substrate :
1. Lactic acid from muscle, erythrocyte
2. Glycerol from TG hydrolysis
3.Glucogenic amino acid
4. Propionic acid in ruminant

26. Gluconeogenesis meets the needs of the body for glucose when carbohydrate is not available from the diet or from glycogenolysis
A supply of glucose is necessary especially for nervous system and erythrocytes.
The enzymes :
1. Pyruvate carboxylase
2. Phosphoenolpyruvate karboxikinase
3. Fructose 1,6-biphosphatase
4. Glucose-6-phosphatase

27. GLUCONEOGENESIS

28. GLUCONEOGENESIS FROM AMINO ACID

29. GLUCONEOGENESIS FROM PROPIONIC ACID

30. CORY CYCLE

31. HMP SHUNT/HEXOSE MONO PHOSPHATE SHUNT = PENTOSE PHOSPHATE PATHWAY
An alternative route for the metabolism of glucose
It does not generate ATP but has two major function :
1. The formation of NADPH synthesis of fatty acid and steroids
2. The synthesis of ribose nucleotide and nucleic acid formation

32. HMP SHUNT
Active in : liver, adipose tissue, adrenal cortex, thyroid, erythrocytes, testis and lactating mammary gland
Its activity is low in muscle
In erythrocytes :
HMP Shunt provides NADPH for the reduction of oxidized glutathione by glutathione reductase reduced glutathi-
one removes H2O glutathione peroxidase

33. HMP SHUNT G-S-S-G 2-G-SH 2-G-SH + H2O2 G-S-S-G + 2H2O
Glutathione reductase
G-S-S-G G-SH
(oxidized glutathione) (reduced glutathione)
Glutathione peroxidase
2-G-SH + H2O G-S-S-G + 2H2O
This reaction is important accumulation of H2O2 may decrease the life span of the erythrocyte damage to the membrane cell hemolysis

34. HMP SHUNT

36. BLOOD GLUCOSE Blood glucose is derived from the :
1. Diet the digestible dietary carbohy-
drate yield glucose blood
2. Gluconeogenesis
3. Glycogenolysis in liver
Insulin play a central role in regulating blood glucose blood glucose
Glucagon blood glucose
Growth hormone inhibit insulin activity
Epinefrine stress blood glucose