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2 digestion pdf Presentation Transcript

  • 1. 1. DigestionDigestion of Carbohydrates • It is the breakdown & degradation of polysaccharides & oligosaccharides into their simplest units (Monosaccharides)
  • 2. Classification of Carbohydrates 3 1 Digestible Do not need digestion 2 Non-DigestibleStarch MonosaccharidesGlycogen Cellulose Pentoses Lactose Hexoses Sucrose
  • 3. TheDigestive System
  • 4. PH 6.4 – 6.9. Activated by Cl-, digests starch to Acidic PH of stomach (1-2) is dextrins, maltose & unsuitable for salivary isomaltose amylase 4. - (Activated by Cl ). 3. Brush border (Intestinal juice,Succus Entericus) containing:Maltase, Lactase & Sucrase
  • 5. Carbohydrate Digestion in Small Intestine• Salivary amylase stops working in acidic stomach (if pH  4.5)• 50% of dietary starch digested before it reaches small intestine• Brush border enzymes act upon oligosaccharides, maltose, sucrose & lactose• lactose indigestible after age 4 in most humans (due to lack of lactase)
  • 6. Carbohydrate Digestion in Small Intestine
  • 7. & Isomaltose
  • 8. 2. Absorption Monosaccharides Absorption• Pentoses are absorbed by facilitated diffusion then excreted through the kidney• Fructose is absorbed by facilitated diffusion then converted to glucose inside the cell• Sodium-glucose transport proteins (SGLT) in membrane help absorption of glucose & galactose
  • 9. Pentoses absorbed by Passive Diffusion According concentration gradient Hexoses absorbed by Active Transport Against concentration gradientAbsorption of Pentoses & Hexoses
  • 10. Types of Transport Carriers
  • 11. Monosaccharides AbsorptionLiver
  • 12. GLUT1 in RBCs membrane is Facilitated Diffusion
  • 13. Digestion of Lactose (Lactase)
  • 14. Lactose Intolerance• Some individuals (90% of adult blacks & Orientals) have a defect in lactase enzyme• Undigested lactose (osmotically active compound) passes to the bowel (large intestine), acted upon by bacteria of large intestine producing short chain fatty acids & CO2 gas, leading to: 1. Abdominal distention (cramping) 2. Abdominal pain 3. Nausea 4. Bloating 5. Watery diarrhea
  • 15. Lactase deficiency
  • 16. Fate of Absorbed Glucose• Glucose enter Liver & Brain by Passive diffusion• Glucose enter other tissues (skeletal muscle, adipose tissue, etc…) by Active transport• Active transport is enhanced by Insulin
  • 17. Utilization of Glucose Anabolic Reactions Catabolic Reactions1) Storage in the form of Glycogen (Glycogenesis)2) Storage in the form of Lipid 1) Glycolysis (Lipogenesis) 2) Kreb’s Cycle3) Synthesis of sugar alcohols 3) Pentose Shunt and amino sugars 4) Formation of4) Interconversion between monosaccharides Uronic acids