Carbohydrates-Absorption

The digestion of carbohydrates starts in the mouth itself and continues into the intestines.

Salivary amylase (ptyalin): the enzyme is capable of acting on polysaccharides like glycogen starch and dextrin’s. It acts on the 1, 4 – glycosidci linkage and liberates maltose C1. And Ca is required as activators. Optimal pH of the enzyme is 6.9. It is inactivated below pH 5.0 pepsin also inactivates the enzyme. Hence the action of the enzyme is of a short duration during the momentary stay of the bolus of food in the mouth and for about fifteen minutes thereafter in the stomach. By that time the highly acidic gastric juice containing pepsin is secreted in sufficient amount to inactivate the amylase.

There is no enzyme in the gastric juice capable of acting on carbohydrates.

Pancreatic amylase (diastase or amylopsin): the action of this enzyme and the conditions of activity are similar to those of the salivary enzyme. The acid chime form stomach is rendered nearly neutral by tehsecretion of bicarbonate rich bile and intestinal secretions besides the bicarbonate present in pancreatic juice itself. The long duration of the stay of the food material in the intestines facilitates complete digestion of the starch and other polysaccharides to maltose.

The glucose molecules linked by 1, 6 linkages at the branching point form is maltose. This is acted upon by is maltase to form glucose.

Intestinal disaccharides (oligosaccharides)

Several disaccharides and oligosaccharides occur in the intestinal brush border. They can digest maltose is maltose lactose sucrose and oligosaccharides produced by amylase digestion. They are according called maltase is maltase lactase surcease and oligosaccharide. The final products of digestion will be glucose fructose and galactose.

Genetic deficiency or total absence of some of these enzymes can occur and give rise to defective digestion and absorption of particular disaccharides. Deficiency of lactase activity in infant’s leads to intolerance to milk and a failure to thrive normally cow milk is tolerated by theses children between than mother milk due to lower lectors’ content of the former.

Lactase activity is high at birth but falls rapidly form age two to five years. It is quite low in adults. These appear to be a racial variation in this. While Europeans retain lactase activity in adult life American black most Asians and Africans have very low lactase activity in adult life. Sucrose activity may be low or absent in some individuals.

As a result of the copied action of the various carbohydrates, all the digestible carbohydrates are converted to monosaccharide’s mainly glucose and smaller amounts of galactose fructose and others.

Absorption of carbohydrates: Only monosaccharides are absorbed. Small intestine is almost exclusively the site of absorption. All monosaccharide are not absorbed at the same rate. The sugars appear to be absorbed by a selective mechanism and not by mere diffusion.