Digestion and Absorption

NCERT Solutions for Class 11 Biology Chapter 16 : Digestion and Absorption

NCERT Solutions for Biology for Chapter 16 Digestion and Absorption Class 11 explains every detail and all the topic of the chapter in-depth. Moreover, the solutions are in simple language and contain all the relevant study material. Also, due to easy language students can easily understand the meaning of each keyword without any difficulty. For a clearer and better understanding of the chapter refer to NCERT Solutions.

These Digestion and Absorption Class 11 Notes for Biology for Chapter 16 will help you in your exam preparation. Moreover, the study material is prepared by our team of professionals will guide you in it. As a result, it will increase your knowledge and learning abilities. Digestion refers to the conversion of complex food in a simpler form so that the body can absorb it to produce energy from it. While absorption refers to the process of absorbing required minerals from the food into the bloodstream.

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Page Number 267
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 the ileum and large intestine
(ii) intestinal juice
(iii) swelling in the neck
(iv) appendix
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  • 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.
  • 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.
Question 2
Match column I with column II.
Column I Column II
(a) Bilirubin and biliverdin (i) Parotid
(b) Hydrolysis of starch (ii) Bile
(c) Digestion of fat (iii) Lipases
(d) Salivary gland  (iv) Amylases
a- i, b- ii, c- iii, d- iv
a- ii, b- i, c- iv, d- iii
a- ii, b- iv, c- iii, d- i
a- iv, b- iii, c- ii, d- i
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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) 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 absorption of nutrients. 
(b) The gastric gland secretes gastric juice which contains pepsinogen, HCl, and mucus. HCl mixed with food and make it acidic when pepsinogen comes in contact with acidic food it gets activated and converts into the pepsin an active enzyme.
(c) The wall of the alimentary canal is made up of four layers serosa, muscularis, submucosa and mucosa.
(d) Bile is secreted by the liver it emulsifies the fats and activates the lipase enzyme for further digestion of fat. 
Question 4
Explain the role of pancreatic juice in digestion.
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Pancreatic juice secreted by the pancreas contains a variety of enzymes, such as trypsinogen, chymotrypsinogen, pancreatic lipase, amylase etc. Trypsin and chymotrypsin help digest proteins; amylase help in digestion of carbohydrates; and lipase to break down fats. So, pancreatic juice helps in digestion of carbohydrates, fats, and protein.
Question 5
Describe the process of digestion of proteins in the stomach.
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The digestion of proteins begins in the stomach. The gastric juice is secreted by the gastric glands, present in the walls of the stomach. The gastric juice contains hydrochloric acid, pepsinogen, mucus, and rennin. Hydrochloric acid helps in conversion of pepsinogen to pepsin. The pepsin converts proteins into proteases and peptides. The mucus helps in the digestion of the food and converting the food into chyme and protects stomach wall from acid. Rennin is a proteolytic enzyme which plays an important role in the coagulation of milk.
Question 6
Give the dental formula of adult human beings.
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The dental formula is used to represent the arrangement of the teeth in upper and the lower row. The dental formula for the adult human beings is 2123/2123. There are 2 incisors, 1 canine, 2 premolars aand 3 molars in one row. There are total 32 teeth in the adult human being
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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The enzyme trypsin (present in the pancreatic juice) activates the inactive enzyme chymotrypsinogen into chymotrypsin.

Chymotrypsinogen Trypsin Chymotrypsin

(Inactive)                                   (Active)

The activated chymotrypsin plays an important role in the further breakdown of the partially-hydrolysed proteins.

ProteinsThe activated chymotrypsin plays an important role in the further breakdown of the partially-hydrolysed proteins. Peptides

The other digestive enzymes of the same category are trypsinogen and carboxypeptidase. These are secreted by the same source-gland, pancreas.

Trypsinogen is present in an inactive form in the pancreatic juice. The enzyme enterokinase – secreted by the intestinal mucosa – activates trypsinogen into trypsin.

Trypsinogenenterokinase Trypsin + Inactive peptide

The activated trypsin then further hydrolyses the remaining trypsinogen and activates other pancreatic enzymes such as chymotrypsinogen and carboxypeptidase. Trypsin also helps in breaking down proteins into peptides.


Carboxypeptidases act on the carboxyl end of the peptide chain and help in releasing the last amino acids.

PeptidesCarboxypeptidasesSmall peptide chain + Amino acids

Question 9
How are polysaccharides and disaccharides digested?
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The polysaccharides and disaccharides are digested by various enzymes produced in the digestive tract. The polysaccharides are broken down to oligosaccharides and disaccharides which are further digested to form monosaccharides are simple sugars.

Digestion of Polysaccharides.
Action of Saliva Starch Maltose Isomaltose - Dextrins
Action of Pancreatic Juice
Starch Maltose Isomaltose -Dextrins
Digestion of Disaccharides
Action of intestinal juice
Maltose Glucose Glucose
Isomaltose Glucose Glucose
Sucrose Glucose Fructose
Lactose Glucose Galactose
Dextrins Glucose
Question 10
What would happen if HCl was not secreted in the stomach?
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Explanation of the answer.

  • HCl causes acidic medium and 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 as a pH of about 1.8 is necessary for proteins to be digested. 

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NCERT Solutions for Class 11 Biology Chapter 16 : Digestion and Absorption

NCERT Solutions for Class 11 Biology Chapter 16 Digestion and Absorption – Brief Overview

16.1 Digestive System

This topic is further divides into various parts but, this topic defines that digestive system consists of the alimentary canal and related glands. 16.1.1 Alimentary Canal - This topic defines what is elementary canal and from where it starts and ends in the body. After that, in the topic the various functions that different parts and organs perform during digestion. Moreover, these parts and organs include Teeth, Oesophagus, Liver, Gall bladder, Stomach, Intestine, and many more organs. Besides, the chapter describes all these things completely. 16.1.2 Digestive Glands - Mainly this gland includes liver, pancreas, and salivary gland. Moreover, the topic describes all these glands and their functions completely.

16.2 Digestion of Food

This topic describes that the process of digestion is completed by a chemical and mechanical process. Also, the topic tells how different cavities and glands help indigestion.
  • Chyme - It is the process of storing the food by the stomach in it for 4-5 hours. After that, it churns and mixes gastric juice in it.
  • Goblet Cells - It refers to that intestinal wall which secretes Mucus.
Apart from this, there are several chemical reactions which tell how the body derive various minerals and elements from food.

16.3 Absorption of Digested Products

It refers to the end process by which digested food passes through the intestinal mucosa into the bloodstream. Facilitated transport - It refers to the process of absorption of glucose and amino acid in the bloodstream by a carrier protein. After that, there is a summary of which organ or part (mouth, stomach, small intestine, and large) absorb which thing.

16.4 Disorders of Digestive System

This topic describes the various abnormalities that the stomach has to face because of tapeworm, hookworm, roundworm, threadworm, and pinworm, etc.
  • Jaundice- It’s a liver infection in which the eyes turn yellow due to bile pigment.
  • Vomiting- It’s a stomach infection in which the food and other intake come out through the mouth.
  • Diarrhea- It’s an abnormality of bowel in which the frequency of movement and liquidity increases.
  • Constipation- In it the bowel movement is irregular and the faeces are retained within the colon.
  • Indigestion- In it, the food is not completely digested which lead to a feeling of a full stomach. Moreover, its causes are inadequate enzyme secretion, food poisoning, anxiety, spicy food, and overeating.
PEM- Protein-Energy Malnutrition (PEM) affects the population during the time of famine, political turmoil, and drought.

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Frequently Asked Questions on NCERT Class 11 Biology Chapter 16 : Digestion and Absorption

Q1. Is Chapter 16 of Biology Digestion and Absorption Class 11 difficult to study?

Answer: No, Chapter 16 of Biology Class 11 is not that difficult to study when you understand the topics. We provide NCERT Solutions and online live classes by experts to clear the doubts and make it easier for the students to understand. These solutions are prepared by the experts to clear the doubts of the students.

Q2. Describe the process of digestion in the stomach?

Answer: The digestion starts in the stomach and it gets completed in the small intestine. The digestive juice secreted by digestive glands which consists of hydrochloric acid, pepsinogen, mucus and rennin. The Proenzyme pepsinogen on exposure to hydrochloric acid converts to an active enzyme called pepsin which is a proteolytic enzyme of the stomach. Pepsin converts proteases into peptones.