ICSE Class 9 Biology Solutions Chapter 11 Digestive system

Class 9th ICSE Biology Solutions Chapter 11 Digestive system

Progress Check

Question 1.
Given below is a jumbled sequence of the different parts of the human alimentary canal. Rewrite them in the space provided in correct sequence. Stomach, Oesophagus, Large intestine, Small intestine, Pharynx.
Answer:
Pharynx-Oesophagus-Stomach-Large intestine-Small intestine.

Question 2.
Name the following :
(i) The three subdivisions of the small intestine :
(ii) The three subdivisions of the large intestine.
(iii) The three salivary glands.
Answer:
(i) Duodenum, Jejunum, Ileum.
(ii) Caecum, Colon, Rectum.
(iii) Parotid, Submaxillary, Sublingual.

Question 3.
Give the technical names for the following types of teeth in humans (on each side, in each jaw)
(i) The three last grinders.
(ii) The pointed tooth for holding and tearing.
(iii) The broad sharp cutting teeth.
(iv) The two temporary (deciduous) grinding teeth.
Answer:
(i) Molars
(ii) Canines
(iii) Incisors
(iv) Premolar.

Question 4.
Name the following parts of a tooth :
(i) Part exposed above the gun.
(ii) The hard substance making the covering of the tooth.
(iii) The soft connective tissue contained in the central space of the tooth.
(iv) Bone-like structure fixing the root in position.
(v) Slight constriction between the root and the crown.
Answer:
(i) Crown
(ii) Enamel
(iii) Pulp
(iv) Cement
(v) Neck.

Progress Check

Question 1.
Mention if the following statements are True (T) or False (F):
(i) Saliva moistens and lubricates food. T/F
(ii) Saliva contains a protein-digesting enzyme. T/F
(iii) Saliva tends to destroy germs in the mouth. T/F
(iv) Peristalsis occurs through all regions of the gut. T/F
(v) The food in stomach stays for about 10 hours. T/F
(vi) Gastric juice is alkaline. T/F
(vii) Gastric juice contains pepsinogen. T/F
Answer:
(i) T
(ii) F
(iii) T
(iv) T
(v) F
(vi) F
(vii) T

Progress Check

Question 1.
Mention if the following statements are True (T) or False (F):
(i) Intestinal villi have a lymph vessel called lacteal. T/F
(ii) Intestine is narrow for fast movement of food. T/F
(iii) Large intestine secretes no enzymes. T/F
(iv) Bile neutralizes the acid content of the food received from stomach. T/F
(v) Pancreatic juice has enzymes to digest all the major components of food. T/F
(vi) Anus is surrounded by circular muscles. T/F
Answer:
(i) T
(ii) F
(iii) T
(iv) T
(v) T
(vi) T

Question 2.
Name the enzyme which, digests
(i) starch in the mouth.
(ii) fats in the ileum.
(iii) protein in duodenum,
(iv) sucrose in the ileum.
Answer:
(i) Starch in mouth-Amylase
(ii) Fats in ileum-Amylopsin
(iii) Protein in duodenum-Trypsin
(iv) Sucrose in ileum-Invertase.

Question 3.
What are the end products of digestion of:
(i) Proteins
(ii) Fats
(iii) Starch
(iv) Sucrose
Answer:
(i) Proteins-Amino acids.
(ii) Fats-Fatty acids and Glycerol.
(iii) Starch-Maltose.
(iv) Sucrose-Glucose and Fructose.

Progress Check

Question 1.
Fill up the blanks :
(i) Liver stores glucose as ………………..
(ii) Liver produces ……………….. only in embryo.
(iii) Urea is produced in ……………….. by the deamination of extra ………………….
(iv) For testing the action of saliva on starch the material has to be kept at a temperature of about ……………….. °C.
Answer:
(i) Glycogen
(ii) Red blood cells
(iii) Liver, Amino acid
(iv) 38.

Progress Check

Question 1.
Mention the constituent of food if the end result of the test shows :
(i) White to yellow and yellow to orange colour (after adding ammonium hydroxide).
(ii) Turning blue-black after adding iodine solution.
(iii) Blue green to deep red with appearance of precipitate when added to Fehling solution.
(iv) Ash that does not burn after continued heating.
Answer:
(i) Protein
(ii) Starch
(iii) Glucose
(iv) Minerals.

Review Questions

A. Multiple Choice Type

Question 1.
Pylorus is an opening from
(a) oesophagus into stomach
(b) mouth cavity into oesophagus
(c) stomach into intestine
(d) intestine into rectum
Answer:
(c) stomach into intestine.

Question 2.
Gastro juice contains
(a) HCI and pepsin
(b) pepsin and trypsin
(c) trypsin and HCI
(d) amylopsin and pepsin
Answer:
(a) HCI and pepsin

Question 3.
The water from the digested food is mainly absorbed by
(a) stomach,
(b) duodenum,
(c) colon,
(d) rectum
Answer:
(c) colon

Question 4.
Which one of the following pairs of types of teeth perform one common function as stated against it?
(a) Iñcisors, canines – Holding
(b) Canines, premolars – Biting
(c) Premolars, molars – Grinding
(d) Molars, incisors – Tearing
Answer:
(c) Premolars, molars – Grinding

B. Very Short Answer Type

Question 1.
What is the dental formula of a normal human adult?
Answer:
\(\frac{2,1,2,3}{2,1,2,3}=32\)

Question 2.
Mention two reflexes which occur when a person chews and swallows food.
Answer:
Reflex when person chews-salivation of mouth.
Reflex when person swallows-Tongue presses upward and back against the roof (Palate).

Question 3.
Consider the following two statements A & B and select the correct option from (i) – (iv) about their correctness.

1. Small intestine is shorter than large intestine.
2. Small intestine is wider than large intestine.

Options:
(i) Both the statements are correct.
(ii) Both the statements are wrong.
(iii) Statement A is correct, B is wrong.
(iv) Statement B is correct, A is wrong.
Answer:
(ii) Both the statements are wrong.

C. Short Answer Type

Question 1.
What is digestion? Why do only animals require a digestive system?
Answer:
Digestion- It is defined as any change which makes the food soluble and of such chemical nature that they can be absorbed through living membranes.
Animals require digestive system as the food that they eat, cannot be utilized as such in the body. It must be changed into a soluble form before it is absorbed into blood and distributed.

Question 2.
What are end-products of the digestion of starch, proteins and fats respectively.
Answer:

• Starch- Maltose.
• Proteins-Amino acids.
• Fats-Fatty acid and glycerol.

Question 3.
Why is there no enzyme to digest vitamins?
Answer:
There is no enzyme to digest vitamins because vitamins act as catalysts or enzymes themselves in essential chemical changes in the body.

Question 4.
How is thorough chewing of food helpful indigestion?
Answer:
Chewing helps in breakdown of complex food substances into simple food which, when mixed with saliva form bolus, so that it can be swallowed easily.

Question 5.
What is the function of the rectum?
Answer:
Rectum temporarily stores undigested food and wastes, to be defecation through anus.

Question 6.
What is roughage? dive two examples.
Answer:

1. Roughage is the undigested portion of the diet.
2. It largely consists of cellulose of the plants e.g., fruits, outer coats of seed and grains, salads, green vegetables.

Question 7.
Mention two ways in which the ileum of a mammal is adapted for the absorption of digested food.
Answer:
Two ways are as follows

1. The Amino acids and simple sugars have relatively small sized molecules which are absorbed by epithelium of villi and reach their blood capillaries.
2. Large molecules like – fatty acids and glycerol are absorbed into the lymph vessel or the lacteal-to enter the lymph.

Question 8.
The stomach secretes gastric juice, which contains hydrochloric acid. What is its function?
Answer:
Stomach secretes hydrochloric acid in the gastric juice. It has two functions namely—

1. It kills any germs which may have entered along with the food.
2. It activates pepsin to act on proteins.

D. Long Answer Type

Question 1.
Prepare a possible vegetarian menu for your dinner which would provide all the necessary nutrients.
Answer:
Menu for dinner

Foodstuffs (in grams)	Veg.
Cereals	320
Pulses	70
Green Leafy Vegetables	100
Other Vegetable	75
Root Vegetables	75
Fruit	75
Milk	600
Fat and oil	30
Brown Sugar and Jaggery	30

Question 2.
What are the main characteristics of an enzyme?
Answer:
Characteristics of an enzyme
1. It is a protein and is therefore, destroyed by heating.
2. It acts only on one kind of substance called the substrate i.e., it’s specific.
3. It always forms the same end products from the substrate.
4. It only affects the rate of a chemical reaction and always speeds up the reaction.
5. Like a catalyst, it can be used again and again.
6. It acts best only at a particular pH i.e., at a particular degree of acidity or alkalinity.
7. It acts best within narrow temperature range usually between 35°-40°C.

Question 3.
Why is the small intestine the most important organ of the digestive system?
Answer:
The small intestine is the most important organ of the digestive system as it serves both for digestion and absorption. It receives two digestive juices

1. Bile
2. Pancreatic Juice.

These two juice virtually cause complete digestion of starch, proteins, carbohydrates, air amylopsin etc. and the small intestine after breakdown of food, absorbs the simple food with small-sized molecules like-amino-acids, glucose etc.

Question 4.
How is the liver an important organ in our body?
Answer:
Liver (Importance)- Liver is the largest gland of the body, weighing about 1500 gm. on an average.
It serves various functions like

• As digestive gland, liver produces bile.
• It regulates blood sugar.
• Excess amino-acids are broken to remove nitrogen part- Deamination.
• Produces RBCs in embryo.
• Produces fibrinogen and prothrombin which are used in blood-clotting.
• Produces heparin.
• Regulates blood volume.
• Destroys dead RBC’s.
• Stores iron, copper and several vitamins.
• Excretes toxic and metallic poisons.
• Produces heat.
• Detoxifies substances including drugs and alcohol.

Question 5.
Define the following terms :
(i) Peristalsis
(ii) Omnivore –
(iii) Pylorus
(iv) Kilocalorie
(v) Basal metabolic rate
Answer:
(i) Peristalsis- Wave of contraction caused by circular muscles of the gut, pushing food along. It occurs through all regions of gut.

(ii) Omnivore- Eat both animal as well as plant as food e.g., crow, human beings.

(iii) Pylorus- Opening of the stomach into intestine is known as pylorus.

(iv) Kilocalorie- 1000 times greater than calories written as Kcal.

(v) Basal Metabolic rate- Amount of calories needed by a person at complete rest.

Question 6.
List the enzymes and their action on food in stomach and intestine.
Answer:

Enzyme	Action
1. Pepsin	Digests proteins into proteoses and peptones
2. Amylopsin	Digests left-over starch into maltose.
3. Trypsin	Acts on remaining proteins, proteoses and peptones to produce peptides and Amino-acids.
4. Steapsin	Acts on emulsified fats to split them into fatty acid and glycerol.
5. Erepsin	Convert the remaining proteins and peptides into Amino acids.

Question 7.
Give any four reasons why water is necessary in our body.
Answer:

1. Water acts as a solvent in the body.
2. Produces digestive juices.
3. It maintains body temperature.
4. Helps in excretion of wastes.

Question 8.
You have been supplied with a sample of food. How will you perform tests for the presence of starch and proteins in it?
Answer:
Test for Starch: A little starch powder is shaken in a test tube with some water and then boiled to make a solution. When the solution is cold, add a few drops of iodine solution, (solution can be prepared by dissolving 1 g iodine and 1 g potassium iodide in 100 mL of distilled water. The solution should be diluted before using). The starch solution would turn blue black indicating presence of starch. Foods like potato and rice give a positive test of starch.

Test for Protein: Place a piece of hard-boiled egg-white in a test tube. Add a few drops of dilute nitric acid just to cover the food. Heat the test-tube gently, then rinse off the acid with water and add ammonium hydroxide. We observe a colour change-first from white to yellow and then (after adding ammonium hydroxide) from yellow to orange.

E. Structured / Application / Skill Type

Question 1.
Draw a labelled diagram to show the internal structure of a mammalian tooth with one and two roots.
Answer:

Question 2.
Try to swallow the saliva in your mouth, and feel your neck with your hand. What happens in the neck?
Answer:
When we swallow saliva the larynx is raised and glottis is closed by epiglottis.

Question 3.
Complete the following table by filling the blanks 1 to 8.

Answer:

1. Stomach
2. Proteins
3. Polypeptides/AminoAcid
4. Ptyalin
5. Starch
6. Ileum
7. Maltose
8. Glucose

Question 4.
Study the diagram given below and then answer the questions that follow:

(a) Name the parts labelled 1, 2, 3, 4, 5 and 6.
(b) Identify the tooth and give a reason to support your answer.
(c) Describe the structure of the part labelled ‘3’.
(d) Give the total number of type of tooth mentioned in ‘1’ above, in the mouth of an adult and state its function.
Answer:
(a)

1. Enamel
2. Dentine
3. Pulp Cavity
4. Neck
5. Crown
6. Cement

(b) Incisor (with one root)

(c) Pulp Cavity: Pulp is the soft connective tissue contained in the central space of the tooth called pulp cavity. It consists of blood capillaries, lymph, vessels and nerve fibres which are continuous below those of the body through the opening of the pulp cavity at the base of the root.
(d)

Type of tooth	Number in half of each jaw	Function Cutting and biting
Incisors Canines Premolars Molars	2 Front teeth the 1 2 3	Food Tearing and piercing Crushing and grinding Crushing, grinding and chewing

Question 5.
Study the following dental formula and then answer the questions that follow:
\(\mathbf{i} \frac{3}{4} \quad \mathbf{c} \frac{0}{0} \quad \mathbf{p m} \frac{0}{1} \quad \mathbf{m} \frac{1}{1}\)
(a) State the total number of teeth present in the dentition.
(b) Is the dentition that of a carnivore or herbivore? Give a reason to support your answer.
(c) Name an animal possessing such a dentition.
(d) Give the dental formula of an adult human being.
Answer:
(a) Dentition = 20
(b) Herbivore – Since the animal lacks canines, which are meant for tearing flesh. But has cutting and grinding teeth.
(c) Squirrel
(d) \(\mathbf{i} \frac{3}{4} \quad \mathbf{c} \frac{0}{0} \quad \mathbf{p m} \frac{0}{1} \quad \mathbf{m} \frac{1}{1}\)

Jumbled Spellings
Write the correct word for the item (i) to (viii)
(i) A predator
GRIET – TIGER

(ii) Deficiency of Folic acid (B₁₁) produces
MIAAAEN – ANAEMIA

(iii) A digestive enzyme.
ENPISP- PEPSIN

(iv) A part of tooth :
TEEDINN- DENTINE

(v) Fatty acids are absorbed into :
TACLELA – LACTEAL

(vi) Maltase acts on :
LESOMAT- MALTOSE

(vii) Excess amino acid are broken down in :
RIVEL – LIVER

(viii) An enzyme which digests starch :
YEALMAS – AMYLASE
Answer:
(i) Tiger
(ii) Anaemia
(iii) Pepsin
(iv) Dentine
(v) Lacteal
(vi) Maltose
(vii) Liver
(viii) Amylase.

Additional Questions

Question 1.
How is the level of glucose regulated by the pancreas?
Answer:
Pancreas is a Exocrine as well as endocrine gland. Pancreas give out a pancreatic duct which secrets pancreatic juice which help in digestion of food. It is also a very important endocrine gland as it produces insulin that controls the amount of sugar in the blood. This gives out hormone: insulin which has the power to convert excess of sugar in to glycogen and it is stored in the liver.

But the pancreas does not produce insulin then the sugar is not converted to glycogens. It become in excess to the blood and is given out along with the urine. The condition is called diabetes. Diabetes may cause heart trouble, kidney failure, blindness and amputation of lower limbs.

Question 2.
Match the following.
1. pancreas – a. adrenalin
2. pituitary gland – b. oestrogen
3. thyroid gland – c. testosterone
4. adrenal gland – d. growth hormone
5. testes – e. insulin
6. ovary – f. thyroxine, g. parathyroxine
Answer:
1. pancreas – e. insulin
2. pituitary gland – d. growth hormone
3. thyroid gland – f. thyroxine
4. adrenal gland – a. adrenalin
5. testes – c. testosterone
6. ovary – b. oestrogen

ICSE Class 9 Biology Solutions