Metabolism of Other Hexoses
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Undergraduate level presentation on Metabolism of Other Hexoses.
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Metabolism of Other Hexoses
- 1. Metabolism of Other Hexoses Group I ( Roll no. 1 – 50) Presenters Kyaw San Lin & KK Thwe Sunn Kaung Kyaw Min & Kay Yu San Slideshow preparation Kyaw Khan Zaw & Kyaw San Lin
- 2. CONTENTS Introduction Fructose metabolism Galactose metabolism Mannose metabolism Summary References
- 3. INTRODUCTION
- 4. Fate of dietary carbohydrates after digestion & absorption – intermediary metabolism End products of carbohydrate digestion – monosaccharides: hexoses and pentoses Principle hexoses – glucose, galactose & fructose 80 – 100% of the total amount absorbed from GI tract - glucose Remaining 20% or less – mannose, galactose & fructose After absorption, all enter the liver and converted mainly to glucose.
- 6. SOURCES Disaccharide sucrose As free monosaccharide
- 7. METABOLISM The entry of fructose into the cells is not insulin dependent.
- 11. DISORDERS OF FRUCTOSE METABOLISM
- 12. EXCESSIVE FRUCTOSE CONSUMPTION Fructose ↑ Fructose 1-P ↑ Pi ↓ ATP ↓ Gluconeogenesis ↓ Hypoglycemia Protein synthesis ↓ Clotting factors & other essential proteins ↓ AMP ↑ AMP degraded Hyperuricaemia Gout DHAP ↑ Glycerol 3-P ↑ entry into glycolysis ↑ Pyruvate ↑ Acetyl CoA ↑ Fatty acid ↑ Hypertriacyl- glycerolaemia Cholestrol ↑ Hypercholes- trolemia Atherogenic
- 13. ESSENTIAL FRUCTOSURIA It is benign and asymptomatic.
- 14. HEREDITARY FRUCTOSE INTOLERANCE (FRUCTOSE POISONING) o Autosomal recessive (1:20,000 births) o Symptoms similar to excessive fructose consumption. o Sucrose & fructose must be removed from the diet.
- 15. FORMATION OF SORBITOL D-Glucose NADPH+ H + NADP + ALDOSE REDUCTASE (not found in liver) D-Sorbitol SORBITOL DEHYDROGENASE NAD+ NADH+H + D-Fructose
- 16. FORMATION OF SORBITOL Increases in activity as the glucose concentration rises In tissues that are not insulin-sensitive Fructose and sorbitol in Lens → Cataract Peripheral nerves → Neuropathy Renal glomeruli → Nephropathy
- 18. SOURCE lactose obtained from milk and its products
- 20. LACTATING MOTHERS In lactating mammary gland If Gal in diet is insufficient
- 21. DISORDER OF GALACTOSE METABOLISM In lactating mammary glandin liver Enters glycolysis If Gal in diet is insufficient in liver
- 22. GALACTOSEMIA Is a severe disease that is inhirited as an autosomal recessive trait ( 1 in 35,000 birth) Physiologic consequences are similar to those found in hereditary fructose intolerance A broader spectrum of tissues is affected. Vomiting diarrhea occurs and enlarge liver with jaundice is common
- 23. GALACTOSEMIA The accumulated galactose is shunted into side pathways such as that of galactitol production. Accumulation of galactitol occurs in lens of the eye → cataract Liver → liver damage Nerve → mental retardation
- 25. SOURCES Vegetables Hydrolysis of mannan gum There is little mannose in dietary carbohydrates
- 26. METABOLISM
- 27. SUMMARY Glucos e Glucose 6-P Fructose 6-P Fructose 1,6-bisphosphate Dihydroxyacetone phosphate Glyceraldehyde 3-PFructose Fructose 1-P Galactose Galactose 1-P Glucose 1-P Mannose Mannose 6-P Glyceraldehyde glycolysis
- 28. REFERENCES Department of Biochemistry: Biochemistry Handbook Volume 3. University of Medicine Mandalay, 2012. Murray RK, Bender DA, et al: Harper’s Illustrated Biochemistry, 28th ed. McGraw Hill, 2009. Harvey R, Ferrier D: Lippincott’s Illustrated Reviews: Biochemistry, 5th ed. Lippincott Williams & Wilkins, 2011. Bray GA, Nielsen SJ, Popkin BM: Consumption of high- fructose corn syrup in beverages may play a role in the epidemic of obesity. Am J Clin Nutr 2004;79:537–43. Glyconutrition ForLife http://www.glyconutritionforlife.org/Science_of_Glyconutri ents/Mannose.php accessed at 8 p.m, 23/7/2012. Medical and healthcare design slides - Templates - Office.com http://office.microsoft.com/en- us/templates/CT010238352.aspx accessed at 8:27p.m.,13/7/2012
- 29. THANK YOU!
Editor's Notes
- First symptoms appear when a baby is weaned from milk and begins to be fed food containing sucrose or fructose. Some of these symptoms may also be responsible for obesity resulting from high fructose diet.
- Nephropathy picture
- UDP-galactose serves as the donor of galactose units in a number of synthetic pathways, including synthesis of lactose, glycoproteins, glycolipids, and proteoglycans.
- The word “mannose” comes from the word ‘Manna”, the foo that was eaten by the Israelites during their wandering through the desert. It is refer to the secretion of tamarisk tree that was plentiful in the Sinai Peninsula during those days. Its resin or wax was sweet to taste and yellow in colour.