Frank Solutions for Chapter 16 Digestive System Class 9 Biology ICSE
Exercises
1. What do you mean by nutrition? Mention the different types.
Answer
Answer
Nutrition can be defined as the process which involves the utilization of food by an animal
to obtain energy for growth and development. There are two types of nutrition -
to obtain energy for growth and development. There are two types of nutrition -
autotrophic and heterotrophic.
2. Define with examples:
(a) Autotrophs
(b) Heterotrophs
(c) Carnivores
(d) Omnivores
(e) Herbivores
Answer
(a) Autotrophs
(b) Heterotrophs
(c) Carnivores
(d) Omnivores
(e) Herbivores
Answer
(a) Autotrophs: These are the organisms which prepare organic food in their body from simple inorganic materials like carbon dioxide, water, etc.
Example - green plants and certain protests.
Example - green plants and certain protests.
(b) Heterotrophs: The organisms which cannot prepare their own food and depends on ready-made food synthesized by green plants are called heterotrophs.
Examples - animals and human beings.
Examples - animals and human beings.
(c) Carnivores: The organisms which feed upon other animals and animal products.
Examples – tiger, lion, cat, etc.
Examples – tiger, lion, cat, etc.
(d) Omnivores: The organisms which feed on all kinds of plant and animal food are called omnivores.
Examples - Cockroach and human beings.
Examples - Cockroach and human beings.
(e) Herbivores: The organisms that feed on plants only are termed as herbivores.
Examples – sheep, cow, goat, etc.
Examples – sheep, cow, goat, etc.
3. State one difference in nutrition:
(a) Parasite and Saprophyte.
(b) Autotroph and Heterotroph.
(c) Holozoic and Saprozoic nutrition.
(d) Holophylic and Holozoic
Answer
(a) Parasite and Saprophyte.
(b) Autotroph and Heterotroph.
(c) Holozoic and Saprozoic nutrition.
(d) Holophylic and Holozoic
Answer
(a) Parasites are the organisms that live in or on the body of another organism called host, and obtain nourishment from its body whereas saprophyte is an organism that absorbs soluble organic nutrients from dead and decaying organic matter.
(b) Autotroph is an organism which prepares organic food in their body from simple inorganic materials like carbon dioxide, water, etc. whereas heterotroph is an organism which cannot prepare its own food and depends on ready-made food synthesized by green plants.
(c) Holozoic nutrition is a nutrition in which animals survive by consuming other organisms whereas saprozoic nutrition is the nutrition in which the animals absorbs soluble organic nutrients from dead and decaying organic matter.
(d) Holophytic nutrition is the nutrition in which organisms prepare organic food in their body from simple inorganic materials like carbon dioxide, water, etc. whereas in holozoic nutrition, the animals survive by consuming other organisms.
4. Name different steps involved in animal nutrition. Explain.
Answer
Answer
The steps involved in animal nutrition are:
- Ingestion - It means taking solid or liquid food inside the body.
- Digestion - It is the breaking down of complex insoluble food components into simple soluble substances.
- Absorption - It is the process by which soluble soluble digested food passes from alimentary canal into blood and lymph through intestinal villi.
- Assimilation - Utilization of absorbed food by different body cells is called assimilation.
- Egestion - Elimination of undigested food as faeces is called egestion.
5. Name the types of teeth in human with functions.
Answer
Answer
There are four types of teeth:
- Incisors - These are used for cutting.
- Canines - These teeth are used for tearing.
- Premolars - For masticating the food.
- Molars - For grinding and masticating the food.
6. Observe the diagram given alongside and answer the following:
(a) Name the parts numbered 1-8.
(b) Which parts shown in the diagram are non-living?
(c) Is the tooth suited for cutting, tearing or grinding?
(d) What is the function of parts 8 and 7?
(e) What is the total number of teeth present in adult human beings?
(f) Write the dental formula of human beings.
(a) Name the parts numbered 1-8.
(b) Which parts shown in the diagram are non-living?
(c) Is the tooth suited for cutting, tearing or grinding?
(d) What is the function of parts 8 and 7?
(e) What is the total number of teeth present in adult human beings?
(f) Write the dental formula of human beings.
Answer
(a) 1. Enamel
2. Dentine
3. Blood capillaries
4. Cement
5. Blood vessels
6. Periodontal membrane
7. Crown
8. root
(b) Enamel, detine and cement
(c) Yes
(d) The function of the root is to hold the teeth in the jaw and the function of the crown is it completely encircles and protects the teeth.
(e) 32
(f) The dental formula of humans is I 2/2, C 1/1, P 2/2, M 3/3 (16×2 =32)
7. Describe the human alimentary canal. Describe the human alimentary canal.
Answer
Answer
Human alimentary canal consists of:
- Mouth - It is the first organ in the sequence which helps in sucking, chewing, salivation and swallowing. The food is ingested through mouth.
- Pharynx - It is situated behind the soft palate and leads into oesophagus. It is divided into three parts- nasopharynx, oropharyx and laryngopharynx.
- Oesophagus - It lies upto the middle of the thorax, behind the trachea and the heart. It pushes the food down into the stomach by peristaltic movements.
- Stomach - It is the widest organ of the alimentary canal. it is J-shaped and is divided into three parts: Cardiac body and pyloric.
- Intestine - It is of two types: Small intestine and large intestine. Small intestine is the longest part of the alimentary canal and comprises of three regions - Duodenum, Jejunum and ileum. It helps in the absorption of food. Large intestine is divisible into three parts - caecum, colon and rectum. It absorbs water from the food.
8. State whether the following statements are True or false:
(a) Trypsin coagulates the milk protein.
(b) Enteropeptidase activates pepsinogen into pepsin.
(c) Na+ is absorbed in intestine by sodium pump.
(d) Pancreatic amylase digests protein into amino acids.
Answer
(a) False
(b) False
(c) True
(d) False
(b) False
(c) True
(d) False
9. Define digestion. Describe the digestion of food in small intestine.
Answer
Digestion - It is the breaking down of complex insoluble food components into simple soluble substances.
Digestion in small intestine:
(a) Digestion of carbohydrates in the small intestine:
40% starch is partially digested by ptyalin while remaining 60% starch is digested by pancreatic amylase.
The enzymes of intestinal juice act as below:
The humans cannot digest the cellulose due to the absence of cellulose enzyme
(b) Digestion of protein the small intestine:
Action of pancreatic juice. It contains proenzymes trypsinogen, chymotry-psinogen and procarboxy peptidase.
Trysinogen converts into trypsin in the presence of enterokinase. trypsin converts chymotrypsinogen into chymotrypsin; procarboxypeptidase into carboxy-peptidase; and peptones into peptides. chymotrypsin also converts peptones into peptides. Peptides gets converted into smaller peptides and amino acids in the presence of carboxyypeptidase.
Action of intestinal juice. Intestinal juice contains endokinase, aminopeptidase and dipeptidase. actions of these enzymes are summarized below:
(c) Digestion of Fats:
Digestion of fats occurs in small intestine and reactions occur as below:
(d) Digestion of Nucleic Acids:
Nucleic acids are digested in the small intestine as below:
The enzyme Dnase converts DNA into Deoxyribonucleotides, Ranse Convert RNA into ribonucleotides, Nucleotidase converts the nucleotides into nucleosides and phosphate and finally nucleoside phosphorylase converts nucleosides into nitrogenous bases and pentose phosphate.
10. Describe protein digestion in the human.
Answer
Digestion of proteins in humans:
There is no digestion of protein in the oral cavity because protein digestive enzymes are absent in the saliva.
(a) Digestion of protein in the stomach:
Gastric juice contains HCl and two proenzyme, pepsinogen and prorennin. HCl maintains a pH of 2-3.7 and kills bacteria and other pathogen. Gastirc juice mixed with food until it becomes semi-solid mass called chyme.
Proenzymes become activated as below:
Theses enzymes act as follows:
(b) Digestion of protein the small intestine
Action of pancreatic juice.. It contains proenzymes trypsinogen, chymotry-psinogen and proocarboxy peptidase.
Action of intestinal juice. Intestinal juice contains endokinase, aminopeptidase and dipeptidase. Actions of these enzymes are summarized below:
11. Describe the following:
(a) Coagulation of milk in the digestive system.
(b) Emulsification.
(c) Digestion of fat in the intestine.
(d) Digestion of nucleic gland.
(a) Coagulation of milk in the digestive system.
(b) Emulsification.
(c) Digestion of fat in the intestine.
(d) Digestion of nucleic gland.
Answer
(a) Rennin is produced by the stomach in an inactive form, called prorennin. After milk is consumed, the gastric acids present in stomach activate the inactive prorennin to active rennin which acts upon casein and converts it into paracasein. Paracasein with the help of calcium ions form calcium paracasin ate or forms coagulated milk. This coagulated milk turns into peptones in the presence of pepsin.
(a) Rennin is produced by the stomach in an inactive form, called prorennin. After milk is consumed, the gastric acids present in stomach activate the inactive prorennin to active rennin which acts upon casein and converts it into paracasein. Paracasein with the help of calcium ions form calcium paracasin ate or forms coagulated milk. This coagulated milk turns into peptones in the presence of pepsin.
These enzymes act as follows:
Paracasein + Ca → Calcium Paracasin ate (Curd)
If milk were not coagulated, it would rapidly flow through the stomach and the digestion of proteins will not take place.
(b) Emulsification: Digestion of fats occurs in small intestine and reactions occur as below:
(c) Digestion of Fats:
Digestion of fats occurs in small intestine and reactions occur as below:
(d) Digestion of Nucleoc Acids:
The enzyme Dnase converts DNA into Deoxyribonucletides, Rnase converts RNA into ribonucleotides, nuckeotidase converts the nucleotides into nucleosides and phosphate and finally nucleoside phosphorylase converts nucleosides and phosphate and finally nucleoside phosphorylase converts nucleosides into nitrogenous bases and pentose phosphate.
Nucleic acids are digested in the small intestine as below:
12. Describe the human salivary gland.
Answer
Salivary Glands - Three pairs in man and secrete 1000 to 1500 cc saliva per day.
Saliva is slightly acidic and its pH is 6.8.
There are three types of salivary glands:
(a) Parotid glands: It is the largest salivary gland and situated near the ears. It opens into oral cavity by Stenoson’s duct.
There are three types of salivary glands:
(a) Parotid glands: It is the largest salivary gland and situated near the ears. It opens into oral cavity by Stenoson’s duct.
(b) Sublingual glands: It is located beneath the tongue. It opens into the floor of oral cavity by duct of Rivinus.
(c) Submadibular or sub-maxillary glands: It is situated at the angles of the lower jaws. It opens inot oral cavity by Whartson’s duct.
Each gland secret secretes saliva which is transported to the mouth cavity. At the
time secrete saliva.
Each gland secret secretes saliva which is transported to the mouth cavity. At the
time secrete saliva.
13. Mark odd one in each series:
(a) Pepsin, lipase, Trypsin, rennin.
(b) Oesophagus, stomach, intestine, lungs.
(c) Bile salts, bile pigment, gall bladder, rectum.
Answer
(a) Pepsin, lipase, Trypsin, rennin.
(b) Oesophagus, stomach, intestine, lungs.
(c) Bile salts, bile pigment, gall bladder, rectum.
Answer
(a) Lipase
(b) Lungs
(c) Rectum
(b) Lungs
(c) Rectum
14. Name the enzymes of pancreatic juice, the substrates they digest and the end products.
Answer
The pancreatic juice contains proenzymes trypsinogen, chymotry-psinogen, procarboxy peptidase, pancreatic amylase and pancreatic lipase.
(a) Digestion of proteins by pancreatic juice: Trysinogen converts into trypsin in the presence of enterokinase. Trypsin converts chymotrypsinogen into chymotrypsin; procarboxypeptidase into carboxy-peptidase; and peptones into peptides. trypsin chymotrypsin and carboxy-peptidase acts upon proteins. Chymotrypsin also converts peptones into peptides. Peptides gets converted into smaller peptides and amino acids in the presence of carboxypeptidase.
(b) Digestion of carbohydrates by pancreatic juice: Pancreatic amylase acts upon starch in the presence of chloride ions and converts it to maltose, isomaltose and dextrin.
(c) Digestion of fats: Pancreatic juice contains pancreatic lipase which emulsifies the fats into fatty acids and glycerol.
15. Match items in column A with the appropriate items in column B:
|
Column A |
Column B |
|
HCl |
Lactose |
|
Rennin |
Pellagra |
|
Enteropeptidase |
Rumen |
|
Cellulose |
Pepsin |
|
Ptyalin |
Starch |
|
Vitamin |
Pernicious anaemia |
|
Intestinal juice |
Trypsin |
|
Bile salt |
Casein |
|
Vitamin A |
Micelle |
|
Goitre |
Night-blindness |
|
Iodine |
Iodine |
Answer
|
Column A |
Column B |
|
HCl |
Pepsin |
|
Rennin |
Casein |
|
Enteropeptidase |
Trypsin |
|
Cellulose |
Rumen |
|
Ptyalin |
Starch |
|
Vitamin |
Pernicious anaemia |
|
Intestinal juice |
Lactose |
|
Bile salt |
Night-blindness |
|
Vitamin A |
Micelle |
|
Goitre |
Iodine |
16. Describe the digestion of starch.
Answer
Digestion of starch
(a) Digestion of starch in the oral cavity: Food is mixed with saliva and salivary amylase or ptyalin converts starch into maltose, isomaltose and limit dextrins.
(b) Digestion of starch in stomach: Gastirc juice does not contain carbohydrate digestive enzyme, hence no digestion of starch takes place in the stomach.
(c) Digestion of starch in small intestine: 40% strch is partially digested by ptyalin while remaining 60% starch indigested by pancreatic amylase.
The enzymes of intestinal juice act as below:
The humans cannot digest the cellulose due to the absence of cellulose enzyme
17. Correct the spellings:
(a) Carboxytipepdase
(b) Reninne
(c) Caceum
(d) HLC
(e) Pespin
(f) Disegion
(g) Ptorein
(h) Bilirubin
(a) Carboxytipepdase
(b) Reninne
(c) Caceum
(d) HLC
(e) Pespin
(f) Disegion
(g) Ptorein
(h) Bilirubin
Answer
(a) Carboxypeptidase
(b) Rennin
(c) Caecum
(d) HCl
(e) Pepsin
(f) Digestion
(g) Protein
(h) Bilirubin
(b) Rennin
(c) Caecum
(d) HCl
(e) Pepsin
(f) Digestion
(g) Protein
(h) Bilirubin
18. Describe the process of digestion in human beings.
Answer
Answer
Digestion of proteins in humans:
There is no digestion of protein in the oral cavity because protein digestive enzymes are absent in the saliva.
(a) Digestion of protein in the stomach: Gastric juice contains HCl and two proenzyme, pepsinogen and prorennin. HCl maintains a pH of 2-3.7 and kills bacteria and other pathogens. Gastric juice mixes with food until it becomes semi-soild mass called chyme proenzymes become activated as below:
These enzymes act as follows:
(b) Digestion of protein the small intestine
Action of pancreatic juice. It contains proenzymes trypsinogen, chymotry-psinogen and procarboxy peptidase.
Action of intestinal juice. Intestinal juice contains endokinase, aminopeptidase and dipeptidase. Actions of these enzymes are summarized below:
19. Name the enzymes secreted by the following:
(a) Stomach
(b) Salivary glands
(c) Pancreas
(d) Ileum
Answer
(a) Stomach - Pepsin
(b) Salivary glands - Salivary amylase/Ptyalin
(c) Pancreas - Trypsin, Chymotrypsin, Carboxy peptidase, Pancreatic amylase and Pancreatic lipase.
(d) Ileum - Enterokinase, Endokinase, Aminopeptidase and Dipeptidase.
(b) Salivary glands - Salivary amylase/Ptyalin
(c) Pancreas - Trypsin, Chymotrypsin, Carboxy peptidase, Pancreatic amylase and Pancreatic lipase.
(d) Ileum - Enterokinase, Endokinase, Aminopeptidase and Dipeptidase.
20. Every question has four options. Choose the correct answer:
(i) Uvila can close the opening of
(a) larynx
(b) gullet
(c) internal nares
(d) eustachian tubes
Answer
(a) Larynx
(ii) Ileum is characterized by
(a) Brunner's glands and leaf-like villi.
(b) Brunner's glands and club-shaped villi.
(c) club-shaped villi and peyer's patches.
(d) Peyer's patches and bunner's glands.
Answer
(c) club-shaped villi and peyer's patches
(iii) The amount of saliva produced per day in human is
(a) 200ml
(b) 500ml
(c) 750-1000ml
(d) liters
Answer
(c) 750-1000 ml
(iv) Liver performs the function of
(a) glycogenesis
(b) glycogenolysis
(c) deamination
(d) all the above
Answer
(d) all the above
(v) The organ that stores bile is
(a) pancreas
(b) glass bladder
(c) spleen
(d) liver
Answer
(b) Gall bladder
(vi) Trypsin is connected with digestion of
(a) proteins
(b) fats
(c) carbohydrates
(d) Vitamins
Answer
(a) Proteins
(vii) Parotid salivary glands occur
(a) below ears
(b) below tounge
(c) at the angle of jaws
(d) below orbits
Answer
(a) Below ears
(viii) vermiform appendix is a constituent of
(a) liver
(b) rectum
(c) stomach
(d) intestine
Answer
(d) Intestine
(ix) Stomach in vertebrates is the chief site of digestion of
(a) protein
(b) carbohydrates
(c) fats
(d) all
Answer
(a) Proteins
(x) Common passage for swallowing food and breathing is
(a) gullet
(b) pharynx
(c) glottis
(d) larynx
Answer
(b) pharynx
(xi) Monophyodont teeth occur in
(a) humans
(b) frog
(c) whale
(d) rat
Answer
(d) Rat
(xii) Teeth present in the upper molar of human beings are
(a) Four
(b) Three
(c) Two
(d) One
Answer
(a) Four
(xiii) Dental formula of human beings is
(a)
(b)
(c)
(d)
Answer
(b) 
(xiv) The hardest constituent of tooth is
(a) bone
(b) dentine
(c) enamel
(d) Pulp
Answer
(c) Enamel
(xv) The number of teeth that grow only once in human is
(a) 4
(b) 12
(c) 20
(d) 28
Answer
(a) 4