Answer briefly: (a) Why are villi present in the intestine and not in the stomach? (b) How does pepsinogen change into its active form? (c) What are the basic layers of the wall of alimentary canal? (d) How does bile help in the digestion of fats?

Answer briefly: (a) Why are villi present in the intestine and not in

1.	Answer briefly: (a) Why are villi present in the intestine and not in the stomach? (b) How does pepsinogen change into its active form? (c) What are the basic layers of the wall of alimentary canal? (d) How does bile help in the digestion of fats?
Answer» Correct Answer - (a) Villi are present in the intestine to increase the area of intestine so that absorption of digsted food occurs efficiently. (b) Pepsingen (inactive form) is first changed by HCI into an active enzyme pepsin. Then, through autocatalysis, more of pepsinogen gets activated to pepsin. Thereafter, pepsin hydrolyses the proteins partially to proteoses and peptones. Pepsinogen + `HCI to` pepsin Proteins `overset("Pepsin")(to)` proteoses and peptones (peptides) (c) The wall of alimentary canal consists of four main concentric coats. Beginning from outside, these coats are -- (iv) Visceral peritoneum (ii) Muscular coat (iii) sub-mucosa, and (iv) mucosa