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
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)
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
Pentoses absorbed by Passive Diffusion According concentration gradient Hexoses absorbed by Active Transport Against concentration gradientAbsorption of Pentoses & Hexoses
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
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
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
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