Digestion is the process of decomposition of food and macronutrients (protein, carbohydrates, fats) into small / basic units and their absorption and transport to target tissues. The aim of the digestion of carbohydrates are the simplest carbohydrates / sugar. that can be absorbed by the intestines and the blood is transferred to the city, where is then metabolized.
Chemical formula of carbohydrates
The original general chemical formula of carbohydrates is (CH2O) n. The relationship between hydrogen and oxygen is therefore 2:1. A newer definition of the group of carbohydrates includes substances for which this ratio is different, but have the characteristics of the “real” carbs. In addition, the formula may also include nitrogen and sulfur.
Division of Carbohydrate
Carbohydrates can be divided into monosaccharides, oligosaccharides and polysaccharides.
Or monosaccharides. divided into simple sugars hexoses (glucose, fructose, galactose, mannose) and pentose (ribose, ribulose, etc..). The intestine can absorb only monosaccharides.
Among oligosaccharides, consisting of 2 to 10 units of simple sugars, including:maltose, which are composed of two molecules of glucose; or sucrose. table sugar is composed of molecules of glucose and fructose; or lactose. milk sugar, which is composed of molecules of glucose and galactose. To digest lactose enzyme lactase needed only that many people lack, this condition is called lactose intolerance. trisaccharide raffinose and melezitose.
Polysaccharides can be divided into digestible (glycogen, starch, etc..) Partially digestible and indigestible. Indigestible polysaccharides or. fiber further divided into insoluble and soluble (hemicellulose, pectin, etc.).
Digestion of carbohydrates
Digestion of carbohydrates begins immediately after eating – in the mouth. By biting the mechanical fragmentation occurs, the enzyme alpha amylase (AA) and proceed with its chemical action – chemical digestion. AA cleaves starch and other polysaccharides into smaller units. In the mouth, food is impregnated with saliva (and hence the AA), so that digestion of carbohydrates takes place in all the way to the stomach, where stomach acid neutralizes the operation of AA.
The digestion then continues in the small intestine where pancreatic AA arrived carbohydrates to cleave even tighter: maltose, maltotriozo, short oligosaccharides, etc..
The last part of the cleavage of di-and oligosaccharides are enforced under the influence of surface enzymes (oligosaccharide and disaharidaze) secreted by cells lining the small intestine – enterocytes. The resulting monosaccharides are then absorbed through enterocito blood.
Di-, oligo-and polysaccharides by alpha-amylase and the small bowel surface enzymes have not been able to break down, they cannot absorb. These saccharides may be used by bacteria that are located on the lower part of the small intestine further, because they have many more types of suitable enzymes – saccharide as a man.
Monosaccharides (mainly as glucose) and then travel through the blood to target tissues, but cannot enter cells by diffusion, since they would have to move against the concentration gradient and therefore to pass through the cell walls need conveyors. These are different for different tissues (6 different transporters: GLUT-1 (Glucose Transporter Briefings type 4), GLUT-2, GLUT-3, GLUT-4, GLUT-5, SGLT-1), all – except for muscle transporter , heart and adipose (GLUT-4) – are independent of the hormone insulin (which means that glucose can cross the cell wall without the presence of insulin).
After eating, the blood glucose is therefore increased, which causes increased secretion of the hormone insulin. Insulin binds to the receptor wall of the target cells (skeletal and cardiac muscle cells and fat cells), which in a cell with a range of reactions that lead to vesicle transport by GLUT-4 transporters, which are stored within the cell to the surface of the cell wall. Vesicles then fuse with the wall, conveyor belts are activated and glucose can cross the cell wall. With the fall of blood glucose reduces the secretion of insulin, insulin receptors are deactivated and transporters are re-stored in vesicles