metabolism of carbohydrate

1. CARBOHYDRATE
METABOLISM
AND
REGULATION OF BLOOD
SUGAR
DR CHIRAG M.A.
Dept of ORAL & MAXILLOFACIAL SURGERY
1

2. CONTENTS
- INRODUCTION
- TRANSPORTATION
- GLYCOLYSIS
- GLUCONEOGENESIS
- GLYCOGENESIS
- GLYCOGENOLYSIS
- HMP SHUNT PATHWAY
- CONCLUSION
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3. INTRODUCTION
 IN PLANTS - CARBONDIOXIDE + WATER
GLUCOSE (STORED AS STARCH OR CONVERTED TO
CELLULOSE)
 IN ANIMALS - FAT + PROTEIN – CONVERTED TO
CARBOHYDRATE
3

4. CLASSIFICATION OF
CARBOHYDRATE
Monosaccharides
ERYTHROSE, RIBOSE, GLUCOSE
Disaccharides
SUCROSE, LACTOSE
Oligosaccharides
MALTOTRIOSE
Polysaccharides
STARCH,CELLULOSE
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5. 5

6. TRANSPORTATION 6

7. GLYCOLYSIS
- EMBDEN MEYERHOF PATHWAY
- ALL CELLS OF BODY
- ONLY SOURCE OF ENERGY FOR ERYTHROCYTE
- SEVERAL STEPS
- ENERGY PRODUCED IS DIFFERRENT FOR AEROBIC AND ANEROBIC
CONDITION
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8. 8

9. 9

10. REGULATION OF
GLYCOLYSISREGULATED BY THREE ENZYMES,
 REACTION 1 HEXOKINASE - INHIBITED BY HIGH LEVELS OF
GLUCOSE-6-PHOSPHATE, WHICH PREVENTS THE
PHOSPHORYLATION OF GLUCOSE.
 REACTION 3 PHOSPHOFRUCTOKINASE - INHIBITED BY HIGH
LEVELS OF ATP AND ACTIVATED BY HIGH LEVELS OF ADP AND
AMP.
 REACTION 10 PYRUVATE KINASE - INHIBITED BY HIGH LEVELS OF
ATP OR ACETYL COA.
10

11. PATHWAYS FOR PYRUVATE
AEROBIC CONDITION
 THREE-CARBON PYRUVATE IS DECARBOXYLATED.
 TWO-CARBON ACETYL CoA AND CO2 ARE PRODUCED.
O O PYRUVATE
|| ||
DEHYDROGENASE
CH3—C—C—O- + HS—CoA + NAD+
PYRUVATE
O
||
CH3—C—S—CoA + CO2 + NADH
ACETYL CoA
11

12. UNDER ANAEROBIC CONDITIONS
 PYRUVATE IS REDUCED TO LACTATE.
 NADH OXIDIZES TO NAD+ ALLOWING GLYCOLYSIS TO CONTINUE.
O O LACTATE
|| || DEHYDROGENASE
CH3—C—C—O- + NADH + H+
PYRUVATE
OH O
| ||
CH3—CH—C—O- + NAD+
LACTATE
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13. 13

14. GLUCONEOGENESIS
GLUCOSE SYNTHESIS
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15. GLUCONEOGENESIS
SITE – MAINLY LIVER BUT ALSO RENAL CORTEX
PARTLY MITOCHONDRIAL PARTLY CYTOPLASMIC
 GLUCOSE SYNTHESIZED FROM NONCARBOHYDRATES
LACTATE, SOME AMINO ACIDS, AND GLYCEROL AFTER
THEY ARE CONVERTED TO PYRUVATE OR OTHER
INTERMEDIATES
 SEVEN REACTIONS ARE THE REVERSE OF GLYCOLYSIS
AND USE THE SAME ENZYMES
 THREE REACTIONS ARE NOT REVERSIBLE.
REACTION 1 HEXOKINASE
REACTION 3 PHOSPHOFRUCTOKINASE
REACTION 10 PYRUVATE KINASE
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17. 17

18. CORI CYCLE/ LACTIC ACID
CYCLE
 IS THE FLOW OF LACTATE AND GLUCOSE BETWEEN THE MUSCLES
AND THE LIVER.
 OCCURS WHEN ANAEROBIC CONDITIONS OCCUR IN ACTIVE
MUSCLE AND GLYCOLYSIS PRODUCES LACTATE.
 OPERATES WHEN LACTATE MOVES THROUGH THE BLOOD STREAM
TO THE LIVER, WHERE IT IS OXIDIZED BACK TO PYRUVATE.
 CONVERTS PYRUVATE TO GLUCOSE, WHICH IS CARRIED BACK TO
THE MUSCLES.
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19. GLYCOGEN METABOLISM 19

20. GLYCOGENESIS
 STORES GLUCOSE BY CONVERTING GLUCOSE TO
GLYCOGEN.
 STORED IN LIVER AND MUSCLES
 USED DURING STARVATION
 DOES NOT OPERATE WHEN ENERGY STORES
(GLYCOGEN) ARE FULL, WHICH MEANS THAT
ADDITIONAL GLUCOSE IS CONVERTED TO BODY FAT.
 FATTY ACID OXIDATION FOR ENERGY AFTER 18 HRS
OF STARVATION
 MUSCLE GLYCOGEN IS RESERVE FOR MUSCLE
CONTRACTION
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21. 21

22. GLUCOSE-6-PHOSPHATE IS CONVERTED
TO GLUCOSE-1-PHOSPHATE
H O CH2
OH
OH
OH
O
O
O CH2
OH
OH
OH
OH
O
P
O
O-
-
O
O
O-
P
O-
22

23. UTP ACTIVATES GLUCOSE-1-PHOSPHATE
TO FORM UDP-GLUCOSE AND
PYROPHOSPHATE (PPI).
O
H
O
N
N
OH OH
O
CH2O
O-
O
PO
O-
O
P
CH2OH
OH
OH
OH
O
O
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24. THE GLUCOSE IN UDP-GLUCOSE ADDS TO GLYCOGEN.
UDP-GLUCOSE + GLYCOGEN GLYCOGEN-GLUCOSE +
UDP
THE UDP REACTS WITH ATP TO REGENERATE UTP.
UDP + ATP UTP + ADP
PRIMER MOLECULE – GLYCOGENIN
ENZYME - GLYCOGEN SYNTHASE
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25. GLYCOGENOLYSIS
 GLYCOGEN IS
BROKEN DOWN TO
GLUCOSE.
 GLUCOSE
MOLECULES ARE
REMOVED ONE BY
ONE FROM THE END
OF THE GLYCOGEN
CHAIN TO YIELD
GLUCOSE-1-
PHOSPHATE.
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26. GLYCOGENOLYSIS
 IS ACTIVATED BY
GLUCAGON (LOW
BLOOD GLUCOSE).
 BONDS GLUCOSE TO
PHOSPHATE TO
FORM GLUCOSE-1-
PHOSPHATE.
GLYCOGEN-GLUCOSE
+ PI
GLYCOGEN +
GLUCOSE-1-
PHOSPHATE
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27. THE GLUCOSE-1-
PHOSPHATE
ISOMERIZES TO
GLUCOSE-6-
PHOSPHATE,
WHICH ENTERS
GLYCOLYSIS FOR
ENERGY
PRODUCTION.
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28. HMP SHUNT PATHWAY
 10% GLUCOSE/DAY IN THIS PATHWAY
 HEXOSE MONO PHOSPHATE PATHWAY
PENTOSE PHOSPHATE PATHWAY (PPP)
DICKENS HORECKER PATHWAY
- GENERATION OF REDUCED NADPH AND
PENTOSE PHOSPHATE FOR NUCLEOTIDE
SYNTHESIS
- TWO PHASES
- OXIDATIVE
- NON OXIDATIVE
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30. SIGNIFICANCE OF HMP
SHUNT
 FOR LIPID SYNTHESIS
 FOR STEROID SYNTHESIS
 FOR RIBOSE SYNTHESIS (REQ FOR NUCLEOTIDE)
 FREE RADICAL SCAVENGING
 DETOXIFICATION OF DRUGS
 ERYTHROCYTE MEMBRANE INTEGRITY
 PRESERVING TRANSPARENCY OF LENS OF EYE
(NADPH IS REQ.)
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31. CARBOHYDRATES IN
DENTAL CARIES
 • FERMENTABLE CARBOHYDRATES CAUSES LOSS OF
CARIES RESISTANCE.
 • CARIES PROCESS IS AN INTERPLAY BETWEEN ORAL
BACTERIA, LOCAL CARBOHYDRATES & TOOTH
SURFACE
 BACTERIA + SUGARS+ TEETH ORGANIC
ACIDS
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CARIES

32. ROLE OF CARBOHYDRATES
IN PERIODONTAL DISEASE
ABNORMAL GLUCOSE
METABOLISM
DIABETES MELLITUS
PERIODONTAL DISEASE
EXCESSIVE CARBOHYDRATE
INTAKE
OBESITY
PERIODONTAL DISEASE
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33. CONCLUSION
 • CARBOHYDRATE ARE THE MEASURE SOURCE OF
ENERGY FOR THE LIVING CELLS. GLUCOSE IS THE
CENTRAL MOLECULE IN CARBOHYDRATE
METABOLISM, ACTIVELY PARTICIPATING IN A
NUMBER OF METABOLIC PATHWAY.
 • ONE COMPONENT OF ETIOLOGY OF DENTAL CARIES
IS CARBOHYDRATE WHICH ACT AS SUBSTRATE FOR
BACTERIA. EVERY EFFORT SHOULD BE MADE TO
REDUCE SUGAR INTAKE FOR HEALTHY TOOTH.
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