DIGESTION AND ABSORPTION OF CARBOHYDRATES

For School Students

1. DIGESTION AND ABSORPTION OF CARBOHYDRATES Prepared by: Richa Khatiwada

2. Digestion : Process of breaking down of food into simpler compounds.

3. Mechanical Digestion Chewing, also known as mastication, crumbles the carbohydrate foods into smaller and smaller pieces to form bolus. Chemical Digestion Salivary glands in oral cavity secrets saliva. Saliva contains enzyme salivary amylase/ptyalin. Salivary amylase hydrolyses starch into maltose and dextrin at pH of 6.8 to 7. Only about 5% starch are broken down in mouth. Digestion in Mouth

4. Mechanical Digestion The strong peristaltic contractions of the stomach mix the carbohydrates into the more uniform mixture of chyme. Chemical Digestion The action of ptyalin continues only inside bolus. About 30-40% of dietary starch is digested before bolus is broken down and acidified. The action of ptyalin is blocked by acidic nature of stomach(pH 1.5). Further breakdown of carbohydrates takes place when the chyme is passed down to the small intestine. Digestion in Stomach

5. Mechanical Digestion There is no mechanical digestion in small intestine. Chemical Digestion The pancreas releases pancreatic juice through a duct. Pancreatic juice contains the enzyme, pancreatic amylase. Enzymes are also secreted by the intestinal cells that line the villi. Digestion in Small Intestine

6. Hydrolyze oligo- and polysaccharides into monosaccharide as follow: Starch pancreatic amylase Maltose + Isomaltose Maltose maltase Glucose +Glucose Isomaltose isomaltase Glucose + Dextrin Dextrin dextrinase Glucose Sucrose sucrase Glucose + Fructose Lactose lactase Glucose + Galactose Action of pancreatic amylase and Intestinal Enzymes

7. Certain carbohydrate like cellulose are undigested by human due to lack of enzymes like cellulase. But ,it provides fibers for absorption of water into the large intestine ,expand the muscle walls and trigger the muscle contractions for egestion. Cure for constipation. Undigested Carbohydrates

8. Digested food from alimentary canal to blood stream. Monosaccharide is absorbed in small intestine. Sodium Glucose Transport Protein(SGLT) in membrane helps absorb glucose and galactose. Fructose absorbed is converted to glucose inside cell. ABSORPTION OF CARBOHYDRATES

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