Digestion and absorption

1. Digestion and absorption Carbohydrates

2. Whenever Zachariah went into the sanctuary where she was, he found that she had food. He said: O Mary! Whence cometh unto thee this? She answered: it is from Allah. Allah gives without stint to whom he will. 37 the family of Imran Al-Qur’an

3. Carbohydrates diet

4. Dietary carbohydrates • Largest source of calories • 40-45% • Plant • starch ( grains, tubers, veggies )sucroseglucose fructosedietary fiber • Animal • glycogenglycolipidslactose

5. Carbohydrates in our diet CH₂OH CH₂OH O O OH OH OH OH OH OH OH OH β-D-glucose α-D-glucose

6. Carbohydrates in our diet CH₂OH CH₂OH O O OH OH OH OH OH OH OH OH β-D-galactose α-D-glucose

7. Carbohydrates in our diet CH₂OH O O HOCH₂ OH OH OH OH OH CH₂OH OH OH β-D-fructose α-D-glucose

8. Carbohydrates in our diet CH₂OH CH₂OH O O OH OH OH OH β-D-glucose α-D-glucose

9. Carbohydrates in our diet CH₂OH O CH₂OH O OH OH OH OH β-D-galactose α-D-glucose

10. Carbohydrates in our diet CH₂OH O O HOCH₂ OH OH OH CH₂OH OH OH β-D-fructose α-D-glucose

11. Carbohydrates in our diet CH₂ O CH₂OH O OH OH OH OH α-D-glucose α-D-glucose

12. Carbohydrates in our diet So what’s our relationship? O α-D-glucose O O Its called α-1—2 glycosidic bond β-D-fructose Sucrose

13. Carbohydrates in our diet Its called β-1—4 glycosidic bond So what’s our relationship? O O O Lactose

14. Carbohydrates in our diet Its called α-1—4 glycosidic bond So what’s our relationship? O O O Maltose

15. Carbohydrates in our diet Of course! It’s the α-1—4 glycosidic linkages So what’s our relationship? O O O O O Maltotriose

16. Carbohydrates in our diet So what’s our relationship? Its called α-1—6 glycosidic bond O O O Iso- maltose

17. Carbohydrates in our diet So what’s our relationship? Its called α-1—1 glycosidic bond , is’nt it cool? O O O Trehalose

18. Carbohydrates in our diet So what’s our relationship? Its called β-1—2 glycosidic bond O O O O O O I don’t understand! Lactulose

19. Carbohydrates in our diet O O O O O O O We’ve got a strong relashionship, the α-1—4 glycosidic linkage Amylose

20. Carbohydrates in our diet We are stronger, we have got α-1—4 glycosidic linkages as well α-1—6 branch points O O O O O O O O O O O Amylo-pectin

21. Carbohydrates in our diet O O O O O O O O We are a team, we have got the β-1—4 glycosidic linkages! Cellulose

22. Carbohydrates digestion

23. Digestion of carbohydrates • Endoglycosidases / exoglycosidases • specific for sugar, type of bond, number of saccharide units • Glycosidases • Enzymes that hydrolyze glycosidic bonds b/w sugars

24. Mouth • Salivary alpha amylase • Endoglycosidase • internal alpha 1,4 bonds • random intervals • No activity against • Alpha 1,6 bonds • Little or no activity against Alpha 1,4 bond at non reducing ends

25. Salivary α-amylase O O O O O O O O O O O O O O O O O O O O O Shortened polysaccharides α-limit dextrins

26. Stomach • Salivary alpha amylase • Inactivated by gastric HCl

27. Small intestine • Pancreatic alpha amylase • Bicarbonate • Intestinal disaccharidases

28. Pancreatic α-amylase • Endoglycosidase • Continues digestion of starch and glycogen • Limit dextrins • Maltotriose • Maltose • Duodenum O O O O O 4-9 glycosyl residues and 1 or more 1,6 branches O O O

29. Intestinal disaccharidases • Glucoamylase • Sucraseisomaltase complex • Lactase glucosylceramidase/ β-glycosidase complex • Trehalase

30. Glucoamylase • Really an oligosaccharidase • Hydrolyses 1,4 bonds of dextrins • Exoglucosidase • Begins at nonreducing end and sequentially cleaves glycosyl units • It cleaves dextrins down to isomaltose • Highest activity in ileum O O O O O O O O O O O O O O O O O O

31. Sucrase-isomaltase complex • Sucrase-maltase • Splits sucrose, maltose and maltotriose • Isomaltase-maltase • Splits alpha 1,6 bonds in isomaltose and limit dextrins • alpha 1,4 bonds in maltose and maltotriose • Jejunum

32. Sucrase-isomaltase complex O O O Sucrose

33. Sucrase-isomaltase complex O O O Maltose

34. Sucrase-isomaltase complex O O O Iso- maltose

35. Lactase glucosylceramidase/ β-glycosidase complex • GlucosylCeramidase • Splits β-glycosidic bonds b/w glucose/galactose and hydrophobic residues • Lactase • Splits β1,4 bonds b/w glucose and galactose • Jejunum

36. β-glycosidase complex O O O

37. Glycolipids • Cerebrosides • Ceramide-monosaccharides • Globosides • Ceramide-oligosaccharides GLU CERAMIDE GLU GAL CERAMIDE

38. Glycolipids • Forssman antigen • Ceramide-oligosaccharides GALNAc GALNAc GAL GAL GLU CERAMIDE

39. Trehalase O O O Trehalose Splits α1,1 bond in trehalose Found in mushrooms,insects and seafood

40. Carbohydrates Absorption

41. Absorption of monosaccharides Hi! • Glucose • Fructose • Galactose • Site • Duodenum • Upper jejunum O O O

42. Na+ O O O Na+ O O O GLUT 5 2K+ Na+ 3Na+ Na+ SGLT-1 GLUT 2 Na+ Na+ Na+

43. Na+ O O O Na+ O O O GLUT 5 GLUT 2 Na+ Na+ SGLT-1 GLUT 2 Na+ Na+ Na+

44. Carbohydrates Indigestible

45. Indigestible carbohydrates • Cellulose • Hemicelluloses • Gums • Mucilages • Pectin • Raffinose • Lignin

46. Colon • Dietary fibre and nondigested carbohydrates • Bacterial action • Gases • H2, CO2, methane • Lactate • Short chain FA • Acetic acid • Propionic acid • Butyric acid

47. What is the cause of excessive flatulence after having a meal containing beans?

48. Carbohydrates Disorders

49. Abnormal degradation of disaccharides • Disorders • Lactose intolerance • Disaccharide intolerance • Isomaltasesucrase deficiency • Defect in absorption of fructose • Symptoms • Osmotic diarrhea • Bacterial fermentation • 2 and 3 carbon compounds • Gases

50. Lactose intolerance • Etiology • Deficiency of enzyme lactase • Clinical features • Abdominal cramps • GI bloating • Intermittent diarrhea • 45min-1hr after eating dairy products