1. Digestion of Roti (Carbohydrates)
(a) Digestion of Carbohydrates in the Oral Cavity
In oral cavity, the roti is mixed with saliva. The saliva contains an enzyme Salivary amylase (ptyalin) which converts Starch in roti into maltose, isomaltose and small - dextrin. 30% of Starch is hydrolysed in the oral Cavity
Starch Maltose + Isomaltose + - Dextrin
(b) Digestion of Carbohydrates in the Small Intestine
The passage of party digested roti from oral Cavity to Oesophagus and then to stomach regulated by peristalsis (the successive waves of muscular contraction in oesophagus). The stomach stores the food for 4-5 hours. The gastric Juice does not contain carbohydrate digesting enzyme.
The partially digested food is now called as chyme. In intestine following action occurs.
(i) Action Pancreatic Juice Carbohydrates in the chyme are hydrolysed by Pancreatic amylase into disaccharides.
Polysaccharides (starch) Disaccharides
(ii) Action of Intestinal Juice Intestinal juice contain maltase, isomaltase, sucrase (invertase), lactase and - dextrinase. These enzymes act on food converting it into simpler compounds like glucose, fructose, galactose, etc.
Maltose Glucose + Glucose
Isomaltose Glucose + Gucose
Sucrose Glucose + Fructose
Lactose Glucose + Galactose
- Dextrins Glucose
2. Digestion of Protein
Proteins are made up of amino acids. So proteins are broken down to amino acid of digestion.
Saliva does not contain any protein digesting enzyme. So, its digestion in stomach.
(a) Digestion of Protein The Stomach The stomach normally stores food for 4-5 hours. The gastric glands of the stomach secrete gastric juice. It contains HCl, proenzymes like - pepsinogen and Prorennin. Various reactions in stomach are discussed below
Proteins Peptones and proteoses
(b) Digestion of Protein in Small Intestine
(i) Action of Pancreatic Juice The enzymes trypsinogen, chymotrypsinogen and procarboxypeptidase in pancreatic juice are all concerned with the protein
digestion.
Some reactions are given below
Trypsinogen Trypsin
Proteins Dipeptides
Chymotrypsinogen Chymotrypsin
Peptones Dipeptides
Procarboxypeptidase Carboxypeptidases
Proteoses Dipeptides
(ii) Action of Intestinal Juice Intestinal juice contain enzymes enterokinase, amino peptidase and dipeptidase andtheir actions are given below
Peptides Amino acid
Dipeptides Amino acid
The macromolecules that are broken down into simpler components are the
products of roti and dal (carbohydrates and proteins) which are further absorbed by the vill in intestine and the rest undigested food is removed in the form of faeces.
