Absorption of carbohydrates ppt

Absorption of carbohydrates ppt

1. Absorption of carbohydrates

2. Digestion of carbohydrates: Carbohydrates are broken down into smaller polysaccharides in the mouth by the action of salivary amylase. Once in the small intestine, pancreatic amylase further breaks the polysaccharide into disaccharides. The three most common disaccharides are maltose, sucrose and lactose. These disaccharide are broken down into monosaccharide by the digestive enzymes found at the brush border of the enterocytes.

3. Maltose is obtain via the digestion of starch by amylase. It consists of two glucose monomers attached via α-1-4 glycosidic bond, which is broken down by the brush border enzyme called maltase . Sucrose consists of glucose and fructose and is broken down by sucrase while lactose consists of glucose & galactose and is broken down by lactase .

4. Absorption of carbohydrates: The principal monosaccharide's produced by the digestion of carbohydrates are glucose, fructose and galactose Glucose accounts for 80% of the total monosaccharide The absorption occurs mostly in the duodenum & upper jejunum of small intestine Only monosaccharaides are absorbed by the intestine

5. Absorption Rates: Cori study: He studies the rate of absorption of different sugars from small intestine in rate Galactose: absorption rate for galactose is maximum Glucose: absorption rate for glucose is moderate Fructose: absorption rate for fructose is minimum

6. Comparison: Glucose absorption as 100, comparative absorption of other sugars as Galactose =110, glucose=100, fructose=43, mannose=19, xylose=15 G alactose is absorbed more rapidly than glucose Pentose are absorbed slowly

7. Mechanism of absorption Different sugars posses different mechanisms for their absorption Examples: Glucose is transported into the intestinal mucosal cells by a carrier mediated and energy requiring process

8. Active transport mechanism Glucose and sodium share the same transport system referred to as sodium dependent glucose transporter The concentration of sodium is higher in the intestinal lumen compared to mucosal cells Sodium moves into the cells along its concentration gradient & simultaneously glucose is transported into the intestinal cells Mediated by same carrier system

9. Sodium diffuses into the cell and it drags glucose along with it The intestinal sodium gradient is the immediate energy source for glucose transport This energy is indirectly supplied by ATP Since the re-entry of sodium (against the concentration gradient) into the intestinal lumen is an energy requiring active process The enzyme sodium potassium ATPase is involved in the transport of sodium in exchange of potassium against the concentration gradient

10. Intestinal absorption of glucose At the intestinal lumen, absorption is by SGluT and at the blood vessel sides absorption is by GLuT2

11. SGuT: Sodium and glucose co-transport system at luminal side; sodium is then pumped out

12. Galactose absorption: Mechanism for absorption of Galactose is similar to that of Glucose

13. Absorption of Fructose: Fructose absorption is simple Does not require energy and Na + ions Transported by facilitated diffusion mediated by a carrier Inside the epithelial cell, most of the fructose is converted to glucose The latter then enters the circulation

14. Absorption of Pentose: Pentoses are absorbed by a process of simple diffusion

15. Factors effecting: Mucus membrane: Mucus membrane is not healthy, absorption will decrease Thyroid hormones: Increases absorption of hexoses & act on intestinal mucosa Adrenal cortex: Absorption decreases in adrenocortical deficiency, mainly due to decreased concentration of sodium Anterior pituitary: It affects mainly through thyroid hormones