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The role of carbohydrates

The ration of proteins, lipids and carbohydrates in food should be 1:1:4, i.e. must be supplied through the diet 400-500g of carbohydrates or 124g per 1000kcal a day.it is desirable that disaccharides made up 25% from this quantity. Overeating of carbohydrates results in obesity and atherosclerosis.

The role of carbohydrates:

1) Energetical function: 99% of carbohydrates is used for energy production. The oxidation of 1g of glucose gives 17,2kj (4,1kcal) of energy;

2) Structural role: formation of GAG, glycoproteins, and other compounds (nucleic acids, nucleoproteins, glycolipids, nucleosidedi and triphosphates, coenzymes, glucuronic acid);

3) reserve function: glycogen is a storage of glucose

4) signal role: receptors and some hormones contain carbohydrates. Carbohydrates stipulate antigenicity of tissues

5) food fibers promotes the retention of water in intestine and formation of feces.

The diet riched by food fibers decreases possibility of appearance of diverticulitis, cancer of large intestine, heart-vessel diseases and diabetes mellitus. Cellulose favourably acts on function of large intestine. Pitch and pectins decrease the level of cholesterol in blood. Perhaps it is due to the binding of bile acids and cholesterol. Pitch and pectins stop evacuation od acydchym from gaster, decrease level of glucose in blood.

The digestion of carbohydrates

The digestion of the starch and glycogen of food beginns in mouth under action of salivary amylase. Gaster doesn’t contain glycosidases, but food undergoes the cleavage under influence of salivary amylase. The action of amylase continues in small intestine. Some other enzymes take part in digestion of starch and glycogen of food, e.g. pancreatic amylase:

(C6H10O5)n + (H2O)n à (Maltose)n

maltose is broken up to 2 glucoses in small intestine under action of maltase (intestinal enzyme)

Lactose is broken up to beta-galactose and glucose in small intestine under action of lactase (intestinal enzyme)

Sucrose is hydrolyzed under action of intestinal sucrase to fructose and glucose:

The digestion of nucleic acids gives pentoses

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