how does protein, carbohydrate & fat digestion take place in alimentary canal?
Answers
Answer:
Digestion is a form of catabolism: a breakdown of large food molecules (i.e., polysaccharides, proteins, fats, nucleic acids) into smaller ones (i.e., monosaccharides, amino acids, fatty acids, nucleotides).
This is a simplified outline of the catabolism of proteins, carbohydrates, and fats. First they break down to amino acids, monosaccharides, and fatty acids respectively. Then these monomers are used to make new polymer molecules or degrade the monomers further into waste products.
Catabolism: A simplified outline of the catabolism of proteins, carbohydrates, and fats.
Carbohydrates are taken in mainly in the form of plant carbohydrate (amylose) and animal carbohydrate (glycogen) together with some sugars, mainly disaccharides. About 80% of the western diet is in the form of amylose. Amylose is not highly branched and consists mainly of long chains of glucose linked by α1:4 linkages.
Cellulose, the most abundant starch in nature, is formed of β1:4 linkages and cannot be digested in humans, although the bacterial action in the colon does break down a minute amount of it.
Glycogen is a multi-branched starch with linkages at the 1:4 and 1:6 position. This creates very large granules of multi-branched starch. Both the parotid and pancreatic amylases hydrolyse the 1:4 link, but not the terminal 1:4 links or the 1:6 links. This breaks amylose down into mainly disaccharides, and glycogen with its 1:6 linkages into polysaccharides.
The net result of these actions are numerous disaccharides and polysaccharides. Enzymes attached to the enterocycytes of the small intestine break these down to monosaccharides.
This is a diagram of hydrolysis by amylase. It shows how both the parotid and pancreatic amylases hydrolyze the 1:4 link, but not the terminal 1:4 links or the 1:6 links.
Hydrolysis by amylase: Both the parotid and pancreatic amylases hydrolyse the 1:4 link, but not the terminal 1:4 links or the 1:6 links.
Proteins and polypeptides are digested by hydrolysis of the carbon–nitrogen (C–N) bond. The proteolytic enzymes are all secreted in an inactive form, to prevent auto-digestion, and are activated in the lumen of the gut. Activation is caused by HCl in the case of the stomach enzyme pepsinogen, and by enteropeptidase and trypsin in the case of the pancreatic enzymes.
Final digestion takes place by small intestine enzymes that are embedded in the brush border of the small intestine. The enzymes are divided into endo- and exo-peptidases.
Answer:
>Protein is digested by a chemical called pepsin
>Carbohydrates are digested by Amylase
>fats are digested by lipase
*Note = The enzymes listed here are the major ones involved. There are many other chemicals too which help in the digestion of these molecules. Also, the complete digestion of food takes place in the small intestine where the liver juices act on the food to further break them down.