Bology class 11 - Absorption and Assimilation of Carbohydrates

Bology class 11 - Absorption and Assimilation of Carbohydrates

Absorption and Assimilation of Carbohydrates

The metabolism of carbohydrates is the process of getting the carbohydrates in the foods we eat into the form that provides fuel to our body’s cells. This process involves digestion, absorption, and transportation to various cells of the body for its utilization (i.e. assimilation). Most commonly, carbohydrate metabolism results in the production of glucose molecules which are the most efficient source of energy for our muscles and our brains. Energy or fuel from our food is used for cell growth, repair, and normal cell functioning.Carbohydrates are broken down to provide glucose for energy. Digestion predominantly occurs with the help of enzymes lining the wall of the small intestine. Once absorbed, galactose and fructose are metabolized further by the liver to produce glucose and minimal amounts of other metabolites.

The digestion process of polysaccharides such as starch will begin in the mouth where it is hydrolyzed by salivary amylase. The amount of starch hydrolyzed here is often quite small as most food does not stay in the mouth long. Once the food bolus reaches the stomach the salivary enzymes are denatured. As a result, digestion predominantly occurs in the small intestine with pancreatic amylase hydrolyzing the starch to dextrin and maltose.

Enzymes classed as glucosidases on the brush border of the small intestine break down the dextrin and maltase, lactase and sucrase convert the other disaccharides into their two monosaccharide units.

Absorption & transport

The monosaccharide units, glucose, galactose, and fructose are transported through the wall of the small intestine into the portal vein which then takes them straight to the liver. The mode of transport varies between the three monosaccharides. Absorption of glucose entails transport from the intestinal lumen, across the epithelium, and into the blood. The transporter that carries glucose and galactose into the enterocyte (epithelial cells that help in absorption of digested food in the small intestine) is the sodium-dependent hexose transporter, known more formally as SGLUT-1.As the name indicates, this molecule transports both glucose and sodium ion into the cell and in fact, will not transport either alone.

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