Free NCERT Solutions For Class 11 Biology Chapter 16 : Digestion & Absorption Free PDF Download

Question 1: Choose the correct answer among the following:
(a) Gastric juice contains
(i) pepsin, lipase and rennin
(ii) trypsin lipase and rennin
(iii)trypsin, pepsin and lipase
(iv)trypsin, pepsin and renin
(b) Succus entericus is the name given to
(i) a junction between ileum and large intestine
(ii) intestinal juice
(iii)swelling in the gut
(iv)appendix

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(c) (a) Gastric juice contains
(i) Pepsin, lipase, and rennin
Gastric juice contains pepsin, lipase, and rennin. Pepsin is secreted in an inactive form as
pepsinogen, which is activated by HCl. Pepsin digests proteins into peptones. Lipase breaks
down fats into fatty acids. Rennin is a photolytic enzyme present in the gastric juice. It helps in
the coagulation of milk.
(b) Succus entericus is the name given to
(ii) Intestinal juice
Succus entericus is another name for intestinal juice. It is secreted by the intestinal gland. Intestinal juice contains a variety of enzymes such as maltase, lipases, nucleosidases, dipeptidases, etc.

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Column 1 Column II

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?

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(a) Villi increases the surface area for more efficient food absorption in small intestine. As
major part of absorption takes place in small intestine, hence the presence of villi is found
in intestine and not in stomach.

Question 4: State the role of pancreatic juice in digestion of proteins.

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Question 5: Describe the process of digestion of protein in stomach.

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Question 6: Give the dental formula of human beings.

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Question 7: Bile juice contains no digestive enzymes, yet it is important for digestion. Why?

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Bile is a digestive juice secreted by the liver. Although it does not contain any digestive enzymes, it plays an important role in the digestion of fats. Bile juice has bile salts such as bilirubin and biliverdin. These 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 activates lipase.

Question 8: Describe the digestive role of chymotrypsin. Which two other digestive enzymes of the same category are secreted by its source gland?

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Question 9: How are polysaccharides and disaccharides digested?

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Question 10: What would happen if HCl were not secreted in the stomach?

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Hydrochloric acid is secreted by the glands present on the stomach walls. It dissolves bits of food and creates an acidic medium. The acidic medium allows pepsinogen to be converted into pepsin. Pepsin plays an important role in the digestion of proteins. Therefore, if HCl were not secreted in the stomach, then pepsin would not be activated. This would affect protein digestion. A pH of about 1.8 is necessary for proteins to be digested. This pH is achieved by HCl.

Question 11: How does butter in your food gets digested and absorbed in the body?

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Question 12: Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal.

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Question 13: Explain the term thecodont and diphyodont.

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Thecodont is a type of dentition in which the teeth are embedded in the deep sockets of the jaw bone. Ankylosis is absent and the roots are cylindrical. Examples include living crocodilians and mammals. Diphyodont is a type of dentition in which two successive sets of teeth are developed during the
lifetime of the organism. The first set of teeth is deciduous and the other set is permanent. The deciduous set of teeth is replaced by the permanent adult teeth. This type of dentition can be seen in humans.

Question 14: Name different types of teeth and their number in an adult human.

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Question 15: What are the functions of liver?

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Liver is the largest and the heaviest internal organ of the body. It is not directly involved in digestion, but secretes digestive juices. It secretes bile which plays a major role in the emulsification of fats.