This chapter belongs to a previous NCERT/CBSE curriculum and is not part of the current 2026-27 chapter list. Removed in 2022-23.
Welcome to the NCERT Solutions for Class 11 Biology - Chapter Digestion and Absorption. This page offers a step-by-step solution to the specific question from Exercise 1, Question 3:
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 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?
(a) The mucosal wall of the small intestine forms millions of tiny finger-like projections known as villi. These villi increase the surface area for more efficient food absorption.
Within these villi, there are numerous blood vessels that absorb the digested products of proteins and carbohydrates, carrying them to the blood stream. The villi also contain lymph vessels for absorbing the products of fat-digestion. From the blood stream, the absorbed food is finally delivered to each and every cell of the body.
The mucosal walls of the stomach form irregular folds known as rugae. These help in increasing the surface area to volume ratio of the expanding stomach.
(b) Pepsinogen is a precursor of pepsin stored in the stomach walls. It is converted into pepsin by hydrochloric acid. Pepsin is the activated form of pepsinogen.
Pepsinogen -------HCL--------> Pepsin + Inactive peptide
(Inactive) (Active)
(c) The walls of the alimentary canal are made up of four layers. These are as follows:
(i) Serosa is the outermost layer of the human alimentary canal. It is made up of a thin layer of secretory epithelial cells, with some connective tissues underneath.
(ii) Muscularis is a thin layer of smooth muscles arranged into an outer longitudinal layer and an inner circular layer.
(iii) Sub-mucosa is a layer of loose connective tissues, containing nerves, blood, and lymph vessels. It supports the mucosa.
(iv) Mucosa is the innermost lining of the lumen of the alimentary canal. It is mainly involved in absorption and secretion.
(d) Bile is a digestive juice secreted by the liver and stored in the gall bladder. Bile juice has bile salts such as sodium glycocholate and sodium tayrocholate which break down large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This process is known as emulsification of fats. Bile juice also makes the medium alkaline and also due to presense of NaHCO3 activates lipase.
NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:
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Welcome to the NCERT Solutions for Class 11 Biology - Chapter . This page offers a step-by-step solution to the specific question from Excercise 1 , Question 3: Answer briefly: (a) Why are villi present in the intestine and not in the stomach? (b) How does pe....
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Than you so much sir and try to short answers ok sir
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Nice
Thank upload for textual questions
Or update karte raheye
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Or update karte raheye
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