NIOS Class 12 Biology Chapter 13 Nutrition and Digestion

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NIOS Class 12 Biology Chapter 13 Nutrition and Digestion

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Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Biology Chapter 13 Nutrition and Digestion Solutions, NIOS Senior Secondary Course Biology Solutions for All Chapter, You can practice these here.

Nutrition and Digestion

Chapter: 13

MODULE – II: FORM AND FUNCTION OF PLANTS AND ANIMALS

NIOS TEXTBOOK QUESTIONS ANSWERS

INTEXT QUESTIONS 13.1

1. List the five major steps in animal nutrition.

Ans: Five major steps in animal nutrition are:

(i) ingestion.

(ii) digestion.

(iii) absorption.

(iv) assimilation. and 

(v) egestion.

2. What is intracellular digestion? Give example of an organism showing intracellular digestion.

Ans: All the five steps of digestion take place inside cell itself, Paramecium and Amoeba, etc. 

INTEXT QUESTIONS 13.2

1. Match the characteristics in column A with the parts of digestive system in Column B.

Ans: 

2. Name the three salivary glands and mention their location.

Ans: Salivary Glands and Their Location: 

INTEXT QUESTIONS 13.3

1. How is grinding of food in the mouth helpful in digestion?

Ans: In the mouth food is ground and small are formed. They (small particles) proparticles vide larger surface area for digestive function.

2. Name the source gland for following enzymes:

(i) amylase.

Ans. Amylase: Salivary glands.

(ii) pepsin.

Ans. Pepsin: Gastric glands.

(iii) lipase. 

Ans. Lipase: Pancreas gland.

3. List at least four enzymes that contribute towards digesting proteins.

Ans: (i) Pepsin.

(ii) Trypsin.

(iii) Erepsin/carboxypeptidase. and 

(iv) Chymotrypsin.

INTEXT QUESTIONS 13.4

1. In which part of the alimentary canal does maximum absorption of water occur?

Ans: In large intestine (colon).

2. List any three ways in which the intestine increases the surface area for absorption?

Ans: (i) It is very long part of digestive canal.

(ii) It has villi-finger like projections.

(iii) Epithelial cells have microvilli.

3. Which end products of digestion are absorbed by:

(i) Blood capillaries of intestinal villi?

Ans: Simple sugars as well as amino acids.

(ii) Lacteals?

Ans: Fatty acids and glycerols.

INTEXT QUESTIONS 13.5

1. Mention the source of secretion and the effect of the following:

(i) Gastrin.

Ans: Gastrin: Stomach, stimulates secretion of gastric juice.

(ii) Enterogastrone.

Ans: Enterogastrone: Duodenum, stops secretion of gastric juice. 

INTEXT QUESTIONS 13.6

1. Name any three substances related to the blood, produced by liver. 

Ans: (i) Heparin.

(ii) Prothrombin. and 

(iii) Fibrinogen (a blood protein).

2. List any three substances which the liver stores.

Ans: (i) Glycogen.

(ii) Iron. and 

(iii) vitamin A, B₁₂ and D.

3. What happens to excess amino acids absorbed from gut?

Ans: Excess amino acids are broken down to produce sugar and urea. The sugar is used but urea is excreted out from body.

INTEXT QUESTIONS 13.7

1. (a) A doctor advises a person to sip ORS at regular intervals because he/she was suffering from diarrheoa. What is this ORS?

Ans: Oral Rehydration Solution: It is drinking water having a pinch of sugar & salt” Its Consumption prevents dehydration.

(b) Name any one causative agent of diarrhoea in developing countries.

Ans: Rota virus or E. coli (bacterium).

(c) During the rainy season there is a rise in diarrhoea cases. What piece of advice will you give to your younger brother/sister to prevent oneself from getting diarrhoea?

Ans: (i) Always wash your hands with soap & water before eating.

(ii) Always wash raw vegetables well before cooking or eating.

(iii) Cover food to check flies.

2. A little girl/boy had a problem in passing stool. The faeces were dry and hard. The doctor said that this was because the child was not taking adequate amount of fibres in the diet and was not taking proper diet at proper time. What is this child suffering from?

Ans: Constipation.

3. What is dyspepsia? What are its symptoms?

Ans: Indigestion upset stomach.

Symptom: Pain in stomach.

4. Which organ of the body is involved in jaundice and how can you make out that a person is suffering from jaundice. 

Ans: Liver. Urine & eyes look

TERMINAL EXERCISES

1. Explain the term “autotrophs”. How are animals different from plants with regard to their mode of nutrition?

Ans: Autotrophs: Organisms which prepare their own food are called autotrophs, e.g. all green plants. They are capable of preparing their own food by CO₂ and H₂O in the presence of sunlight and chlorophyll. Animals are heterotrophs. They cannot make their own food.

2. Enlist at least ten organs of the alimentary canal of man.

Ans: Ten organs of the alimentary canal of man are: Mouth, teeth, buccal cavity, pharynx, oesophagus, stomach, intestine, colon and rectum.

3. Define the term “digestion”. List the digestive processes occurring in the small intestine.

Ans: Digestion: It is “the conversion of insoluble complex food into soluble simple components or particles. Most of the digested food is absorbed the small intestine by osmosis, diffusion and active transport.”

4. How does digestion of carbohydrates and proteins take place in humans?

Ans: Digestion of Carbohydrates and Proteins in Humans: Carbohydrate digestion starts in the mouth or buccal cavity. Saliva is mixed with food and ptylin (salivary amylase) acts on starch to form maltose. 

Starch + Salivary amylase → Maltose

There is no digestion of carbohydrates in the stomach. In small intestine pancreatic amylase digests starch and sugar.

In intestine,

Maltose + Maltase → Glucose (C₆H₁₂O₆).

Lactose + Lactase → Glucose + Galactose

Sucrose + Sucrase → Glucose + Fructose

Protein digestion: It occurs in stomach and intestine by proteases enzymes like Renin, pepsin, trypsin, chymotrypsin and carboxy-peptidases.

5. Explain the role of the following in the digestive process in humans:

(a) Gastrin.

Ans: Gastrin: This hormone is produced by the gastric cells and stimulates the secretion of gastric juice.

(b) Hydrochloric acid.

Ans: Hydrochloric Acid: Gastric juice contains 0.5% HCl. It is secreted by parietal cells in the stomach wall.

(i) It kills bacteria.

(ii) It activates inactive pepsinogen to form active pepsin.

(iii) It loosens fibrous material found in the food.

(iv) It maintains acidic medium for digestion of food.

(v) It curdles milk also.

(c) Secretin.

Ans: Secretin: This hormone is secreted by the duodenal epithelium. It stimulates the flow of pancreatic juice.

6. Write short notes on:

(a) absorption of the digested food.

Ans: Absorption of Digested Food: Absorption of digested food occurs in the stomach and intestine mainly. However in mouth water, water soluble vitamins and glucose are absorbed. In stomach glucose, water, alcohol, vitamin and some drugs may be absorbed.

Mostly absorption occurs in the small intestinal through the villi which increase surface area. Monosaccharides and amino acids are absorbed into the blood capillaries of the villi. Fatty acids and glycerol are absorbed by the larger lymph vessels called lacteals.

(b) assimilation.

Ans: Assimilation: Absorbed food is made usable by the cells in body. Amino acids form proteins while excess of amino acids are removed. They form sugars. The digested sugars after absorption are converted into glycogen by the liver. Fatty acids and glycerol form fats (either used or stored in adipose tissues).

(c) defaecation.

Ans: Defaecation: It is called egestion. It is the passing out of undigested food materials from the body. The undigested food mainly consists of plant fibres, bacteria, etc. They are stored in rectum for some time. Water is absorbed and the faeces become semi solid or solid. They are passed out through the anus.

(d) role of liver in metabolism.

Ans: Role of Liver in Metabolism: Liver plays an important role in metabolism. It is digestive as well as secretory in function. It emulsifies fats through the bile. It forms red blood cells in embryonic stage. It produces fibrinogen and prothrombin. It secretes heparin. It stores blood. It destroys dead and worn out RBCs. It stores iron, vitamin A, D and B₁₂. It also removes toxic substances from the blood. Its role in metabolism is given below:

(i) It regulates blood sugar. It stores glycogen and releases it as glucose when required.

(ii) It breaks down amino acids into sugar and urea. Urea is excreted out in urine.

(iii) It makes fatty acids from the carbo-hydrates.

7. Name the enzymes concerned with the digestion of various carbohydrates, the region of the gut where they act and their products in the table given below: 

Ans:

8. Bile has no digestive enzyme yet it plays a key role in digestion. What is it role?

Ans: Bile: It is secreted by the liver and stored in gall bladder. It is pale yellow fluid. Its yellow color is due to the pigments like bilirubin and biliverdin that are produced by breakdown of dead and worm out red blood corpuscles. These pigments are excreted in faeces (in solid and undigested food). It emulsifies the fates. It has no enzyme. It furnishes alkaline medium. 

9. Draw a well-levelled diagram of alimentary canal in humans.

Ans. Alimentary Canal of Humans: See Fig.

Fig. 13.4. Alimentary canal and the associated glands of man.

10. List common digestive disorders. Add a note on ORS. 

Ans: Common Digestive Disorders: Vomiting, diarrhoea, indigestion, constipation and jaundice. 

ORS = Oral Rehydration solution.

It given to patients suffering from diarrhoea and vomiting digestive disorders. ORS is a special powder containing sugar and salts in specific amounts. It is converted into liquid by mixing water.