Answer:
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 dextrins called a-dextrin. 30% of
starch is hydrolysed in the oral cavity.
Starch Maltose + Isomaltose
+ a-Dextrin
(b)
Digestion of Carbohydrates in the Small Intestine
The passage
of party digested roti from oral cavity to oesophagus and then to stomach is
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 contajn
carbohydrate digesting enzyme.
The
partially digested food is now called as chyme. In intestine, following action occurs.
(i) Action
of 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, sucrose (invertase),
lactase and a-dextrinase These enzymes act on food converting it into simpler
compounds like glucose, fructose, galactose, etc.
2. Digestion
of Protein
Proteins are
made up of amino acids. So proteins are broken down to amino acid during the
process of digestion.
Saliva does
not contain any protein digesting enzyme. So, its digestion in stomach.
(a) Digestion
of Protein in Stomach The stomach normally stores food for 4-5 hours.
The gastric
glands of the stomach secrete gastric juice. It contains HCI, proenzymes
like-
pepsinogen and prorennin. Various reactions in stomach are discussed below
Proteins Peptones and
proteoses
Prorennin
(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 and their 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 villi in
intestine and the rest undigested food is removed in the form of faeces.
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