Karnataka 1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

1st PUC Biology Digestion and Absorption One Marks Questions and Answers

Question 1.
What is succus entericus?
Answer:
It is the intestinal juice.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 2.
What is hyperacidity?
Answer:
Hyperacidity is a condition where there is an over-secretion of HCl in the stomach.

Question 3.
Name any two associated glands of the human alimentary canal.
Answer:
Salivary gland, Liver / Pancreas.

Question 4.
What is Chyme?
Answer:
The acidic semisolid food entering into the intestine from stomach, is called as chyme.

Question 5.
Mention the function of steapsin.
Answer:
Steapsin hydrolyses fat emulsion, into fatty acids, and glycerol.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 6.
What is the function of caecum in the human body?
Answer:
Caecum is present at the junction of small and large intestines, and it connects the small and large intestines.

Question 7.
What is mastication?
Answer:
Mastication is the process of chewing of food. Teeth plays an important role.

Question 8.
What is bolus?
Answer:
Bolus is the soft mass of the semi – masticated food along with the addition of saliva in the mouth.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 9.
Where is the bile stored?
Answer:
In the gall bladder.

Question 10.
Mention the position of the liver.
Answer:
It is located below the diaphragm towards the right side of the abdominal cavity.

Question 11.
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 rennin.
Answer:
(i) pepsin, lipase and rennin.

(b) Succus entericus is the name given to,
(i) a junction between the ileum and large intestine.
(ii) intestinal juice.
(iii) swelling in the gut.
(iv) appendix.
Answer:
(ii) intestinal juice.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

1st PUC Biology Digestion and Absorption Two Marks Questions and Answers

Question 1.
Explain the role of saliva indigestion.
Answer:
Salivary amylase acts on starch and glycogen and converts them into maltose units.
\(\text { Starch, Glycogen + Water } \frac{\text { Salivary amylase }}{\mathrm{pH} 6.8 \mathrm{to} 7.2}{\longrightarrow} \text { Maltose units. }\)
The water and mucin soften the food particles. The lysozyme destroys the bacteria.

Question 2.
Distinguish between mechanical digestion from chemical digestion.
Answer:

Mechanical digestion Chemical digestion
1.   It is a process in which there is cutting, chewing by teeth, and churning of food in alimentary canal.
2.  Enzymes are not involved.
1.   It is a process in which hydrolysis of the enzymes takes part in the breaking of the food molecules.
2.   Enzymes are involved.

Question 3.
What is Dentition? Write the dental formula of human beings.
Answer:
Dentition is the arrangement of teeth in the oral cavity. The human dentition is defined as.
Thecodont : Teeth are located within the sockets of jaw bone.
Diphyodont: Humans develop two sets of teeth in his life time, i.e., milk teeth, and permanent teeth set.
Heterodont: Teeth are of different types like incisors, canines, molars, and premolars.
The dental formula of man is
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption.1

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 4.
What is Jaundice? Mention the types.
Answer:
Jaundice is the yellowing of the skin and sclera of the eyes, due to excess bilirubin in the blood. The different types of jaundice are:
a. Haemolytic jaundice
b. Obstructive jaundice
c. Viral jaundice

Question 5.
Mention the role of HCl in digestion.
Answer:
a. It activates inactive pepsinogen into active pepsin.
b. It converts inactive prorenin into active renin.
c. It provides acidic medium (pH 1.5 – 2.5) for the action of both pepsin, and renin.
d. HCl kills harmful bacteria, and loosens fibrous food.
e. It inactivates the ptyalin.

Question 6.
Name the various parts of human alimentary canal in the proper sequence.
Answer:
The various parts of human alimentary canal are mouth buccal cavity, pharynx, oesophagus, stomach, small intestine, large intestine and anus.

Question 7.
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
Answer:
(a) (ii), (b) (iv), (c) (iii), (d) (i).

Question 8.
Give the dental formula of human beings.
Answer:
The dental formula of human
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 3

Question 9.
Bile juice contains no digestive enzymes, yet it is important for digestion. Why?
Answer:
Bile salts help in the emulsification of fats.

Question 10.
Describe the digestive role of chymotrypsin. Which two other digestive enzymes of the same category are secreted by its source gland?
Answer:
Intestinal Glands :
These are present in the inner mucosa of small intestine. There are 4 types of intestinal glands.
they are:
1. Glands of crypts of lieberkuhn.
2. Payer’s glands.
3. Brunner’s glands.
4. Solitaiy. glands.
Out of these glands, crypts of lieberkuhn secretes intestinal juice (Succus entericus), While others secrete an alkaline secretion which protects the intestinal lining from bacterial infection.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Components of Food (Concept of Balanced Diet):
A balanced diet is one which contains the right proportion of the seven nutrients namely carbohydrates, fats, proteins, vitamins, minerals, water, and roughage (Fibrous component)
required to maintain good health.

Carbohydrates and lipids (fats) provide energy for the body. Proteins are required for growth, maintenance and repair of worn out tissues. Water, minerals, and vitamins are essential for
maintaining normal metabolism.

The correct and recommended proportion of balanced diet is represented as follows.
Carbohydrates – 64%, Proteins – 14%, Lipids-2 1%, Vitamins, and minerals -. 1%.
In addition, large amount of roughage consisting of mainly fibrous cellulose is also important.

Question 11.
How are polysaccharides, and disaccharides digested?
Answer:
(a) Digestion in the mouth : The salivary amylase or ptyalin converts starch and glycogen into maltose units.
\(\text { Starch the Glycogen }+\text { Water } \frac{\text { Salivary amylase }}{\mathrm{pH} 6.8 \mathrm{to} 7.2}{\longrightarrow} \text { Maltose units }\)

b. Digestion in intestine :
Pancreatic juice : Carbohydrase secreted by pancreas is called pancreatic amylase. It converts starch and glycogen into maltose units.
\(\text { Starch Glycogen } \frac{\text { Pancreaticamylase }}{\mathrm{pH} 7.1-8.2} \rightarrow \text { Maltose units. }\)

Intestinal juice : It consists of three types of carbohydrases.
Maltase : Maltase catalyses hydrolysis of maltose (disaccharide) into glucose units (monosaccharides).
\(\text { Maltose } \frac{\text { Maltase }}{\mathrm{pH} 7 . \mathrm{to8} .2} \text { Glucose }+\text { Glucose. }\)

Sucrase : Sucrase catalyses the splitting of sucrose (disaccharide) into glucose, and fructose units (monosaccharides).
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 35

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Lactase : Lactase acts on milk sugar lactose (disaccharide), and splits lactose into galactose, and glucose units (monosaccharides).
\(\text { Lactose } \frac{\text { Lactase }}{p H^{7.11082}} \text { Glucose }+\text { Galactose. }\)

Question 12.
What would happen if HCl were not secreted in the stomach?
Answer:
Non-secretion of HCl in the stomach will result in the following.
(i) Food will not become soft, and so it will not be easily broken in stomach.
(ii) Microbes will grow in stomach, and cause fermentation.
(iii) Milk will not be curdled.
(iv) Pepsinogen will not be changed into pepsin.
(v) Pepsin will not be able to bring about digestion of proteins.

Question 13.
How does butter in your food get digested and absorbed in the body?
Answer:
First emulsification takes place by bile juice and digestion by steapsin to are absorbed by.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 14.
Explain the term the codont and diphyodont.
Answer:
The human teeth are Diphyodont because 2 sets of teeth (Milk teeth, and Permanent teeth) are formed during the life time. Human teeth are thecodont because all the teeth are inserted in the sockets. The arrangement of teeth on the jaws is called Dentition. The dental formula of human
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 3

Question 15.
Name different types of teeth and their number in an adult human.
Answer:
The tongue is attached to the buccal cavity by a soft ligamentous structure called Frenum or Frenulum. Tongue helps in ingestion of food substance, mixing the food with saliva, tasting, and also for speech. Both upper and lower jaw contain teeth. In Humans, teeth are heterodont because 4 different types of teeth are present. They are.
(1) Incisors (Cutting teeth)
(2) Canines (Tearing teeth)
(3) Premolars and
(4) Molars (Grinders).

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 16.
What are the functions of liver?
Answer:
It is an accessory gland that is situated outside the Alimentary canal. It is situated just below the diaphragm and attached slightly towards the right side partly covering the stomach. Liver
is the largest gland in the human body, weighing about 1.5 Kg (in adults).
It consists of 4 lobes namely:
1. Right lobe (largest lobe).
2. Left lobe (Smallest lobe).
3. Caudale lobe and
4. Quadrate tobe.
Liver is an exocrine gland because it secretes. Its secretion called bile juice is passed through the bile duct. The bile juice is stored in gall blabber.

Question 17.
Describe the enzymatic action on fats in the duodenum.
Answer:
In duodenum, pancreatic lipase or steapsin is available for digestion of fats. However, digestion is incomplete due to the brief stay of food.

1st PUC Biology Digestion and Absorption Three Marks Questions and Answers

Question 1.
Describe how carbohydrates are digested in the human alimentary canal.
Answer:

(a) Digestion in the mouth : The salivary amylase or ptyalin converts starch and glycogen into maltose units.
\(\text { Starch the Glycogen }+\text { Water } \frac{\text { Salivary amylase }}{\mathrm{pH} 6.8 \mathrm{to} 7.2}{\longrightarrow} \text { Maltose units }\)

b. Digestion in intestine :
Pancreatic juice : Carbohydrase secreted by pancreas is called pancreatic amylase. It converts starch and glycogen into maltose units.
\(\text { Starch Glycogen } \frac{\text { Pancreaticamylase }}{\mathrm{pH} 7.1-8.2} \rightarrow \text { Maltose units. }\)

Intestinal juice : It consists of three types of carbohydrases.
Maltase : Maltase catalyses hydrolysis of maltose (disaccharide) into glucose units (monosaccharides).
\(\text { Maltose } \frac{\text { Maltase }}{\mathrm{pH} 7 . \mathrm{to8} .2} \text { Glucose }+\text { Glucose. }\)

Sucrase : Sucrase catalyses the splitting of sucrose (disaccharide) into glucose, and fructose units (monosaccharides).
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 35

Lactase : Lactase acts on milk sugar lactose (disaccharide), and splits lactose into galactose, and glucose units (monosaccharides).
\(\text { Lactose } \frac{\text { Lactase }}{p H^{7.11082}} \text { Glucose }+\text { Galactose. }\)

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 2.
Answer briefly:
(a) Why are villi present in the intestine, and not in the stomach?
(b) How does pepsinogen changes into its active form?
(c) What are the basic layers the wall of the alimentary canal?
(d) How does bile help in the digestion of fats?
Answer:
(a) To increase surface area for absorption
(b) By HCl action
(c) Serosa, muscular is external, Sub mucosa and mucosa
(d) By the emulsification of fats

Question 3.
State the role of pancreatic juice in digestion of proteins.
Answer:
The Pancreatic juice is secreted from acinar cells (Exocrine part) of the pancreas. it contains the following digestive enzymes namely Trypsin, Carboxypeptidase, Chymotrypsin, Amylopsin (Pancreatic amylase), Steapsin etc.

Trypsin:
It is secreted in an inactive form called Trysinogen. It is activated by non-digestive intestinal enzyme called Enterokinase. Trypsin acts on whole proteins or semi digested, ones and convert them into polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 4

Chymotrypsin:
It is secreted in an inactive form called chymotrypsinogen. It is activated by an enzyme called trypsin. Chymotrypsinogen acts on peptones, proteoses, and convert them into polypeptides
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 5

Question 4.
What are the three major types of cells found in gastric glands? Name their secretions.
Answer:
(i) Peptic or Chief Cells: Pepsinogen, Prorennin and Gastric lipase (in infants).
(ii) Oxyntic or Parietal Cells: HCl.
(iii) Goblet Cells: Mucus.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

1st PUC Biology Digestion and Absorption Five Marks Questions and Answers

Question 1.
Explain the physiology of protein digestion in a human body.
Answer:
Digestion in Stomach:
Gastric juice: Pepsin, and Renin are the proteases present in gastric juice
(i) Pepsin : It is an enzyme produced in an inactive form called pepsinogen. Pepsinogen is activated by HCl. Pepsin is an endopeptidase and it breaks inner peptide bonds of the protein molecule to form proteoses, peptones, and polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 6

(ii) Renin : Renin is also secreted in an inactive form called prorenin. It is activated by HCl. Renin acts on the milk protein called casein, and converts it into paracasein. Paracasein in turn combines with calcium salts, and forms calcium paracaseinate (curdy precipitate).
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 7

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

This process of conversion into calcium paracaseinate is called curdling of milk.
Pancreatic juice : Trypsin, Chymotrypsin and Carboxypeptidase are the proteases secreted by the pancreas.

(i) Trypsin : It is secreted as an inactive trypsinogen. Later gets activated by enterokinase of the intestinal juice. Trypsin is a endopeptidase. It acts on proteins and converts them into Proteoses, Peptones and Polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 8

(ii) Chymotrypsin : It is secreted as an inactive chymotrypsin and later gets activated by trypsin. Chymotrypsin is also an endopeptidase and converts Protein into Polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 9

(iii) Carboxypeptidase: It converts polypeptides into Tripeptides, Dipeptides and Amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 10

Intestinal juice : The four proteases forming the intenstinal juice are Aminopeptidase. Dipeptidase, Tripeptidase and Erepsin.
(i) Aminopeptidase: It is a exopeptidase which acts on the terminal ends of the polypeptides and convert them into Tripeptides, Dipeptides and Amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 11

(ii) Tripeptidase : It acts on the Tripeptide units and converts them into amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 12

(iii) Dipeptidase : It acts on Dipeptide units and converts them into Amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 13

(iv) Erepsin : It is a powerful protease of the intestine. It convert polypeptides, and other short chain Amino acids into free Amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 14

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 2.
Describe the process of digestion of protein in the stomach.
Answer:
Process of Digestion :
During this process, the complex food. molecules such as proteins, carbohydrates, and lipids are converted into smaller molecules such as ammo acid, monosaccharide, fatty acids, and
glycerol respectively.

Digestion in Buccal Cavity:
As soon as the food enters into the buccal cavity, both mechanical and chemical digestion takes place. Mechanical digestion is brought about by the cutting and chewing action of the
teeth. During this pròcess the complex food molecules are converted into smaller molecules. In the mean time, saliva is secreted and mixes with the food.

Question 3.
Discuss the main steps in the digestion of proteins as the food passes through different parts of the alimentary canal.
Answer:

Digestion in Stomach:
Gastric juice: Pepsin, and Renin are the proteases present in gastric juice
(i) Pepsin : It is an enzyme produced in an inactive form called pepsinogen. Pepsinogen is activated by HCl. Pepsin is an endopeptidase and it breaks inner peptide bonds of the protein molecule to form proteoses, peptones, and polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 6

(ii) Renin : Renin is also secreted in an inactive form called prorenin. It is activated by HCl. Renin acts on the milk protein called casein, and converts it into paracasein. Paracasein in turn combines with calcium salts, and forms calcium paracaseinate (curdy precipitate).
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 7

This process of conversion into calcium paracaseinate is called curdling of milk.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Question 4.
Draw a neat labelled diagram of the digestive system of the human body.
Answer:
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption.3

Question 5.
Explain the role of pancreatic juice in digestion.
Answer:
Pancreatic juice :
The exocrine part of pancreas (acini) secretes an alkaline fluid called pancreatic juice. Pancreatic juice contains water, mineral salts and a variety of enzymes, such as one carbohydrase, three types of proteases, one lipase and one nuclease.

a. Carbohydrase : Carbohydrase acts on the carbohydrate molecules. Carbohydrase secreted by pancreas is called pancreatic amylase (amylopsin). It is a powerful enzyme, due to which polysaccharides are converted into disaccharides.

b. Proteases : Proteases are enzymes which act on proteins. Trypsin, Chymotrypsin and Carboxypeptidase are the proteases secreted by the pancreas.

(i) Trypsin : It is secreted as the inactive Trypsinogen. Later gets activated by enterokinase of the intestinal juice. Trypsin is a endopeptidase. It acts on proteins and convert them into Proteoses, Peptones and Polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 16

(ii) Chymotrypsin : It is secreted as the inactive chymotrypsin and later gets activated by Trypsin. Chymotrypsin is also an endopeptidase and converts Protein into Polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 17

(iii) Carboxypeptidase : It is an exopeptidase, acting on the terminal peptide bonds of the polypeptide chain. It converts Polypeptides into Tripeptides, Dipeptides and Amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 18

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

c. Lipase : It is an enzyme which acts on lipids. Lipase secreted by pancreas is called pancreatic lipase or steapsin. It is secreted in an inactive form, and is activated by enterokinase. Pancreatic Lipase is a powerful enzyme and it hydrolyses fat emulsion into Fatty acids and Glycerol.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 19

d. Nuclease : Nuclease splits Nucleic acids into Nucleotides
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 20

1st PUC Biology Digestion and Absorption Text Book Questions and Answers

Definition:
The physiological process of breaking up of complex insoluble food materials into simple, soluble substances is called Digestion.
or
Digestion is a catabolic process involving the enzymatic hydrolysis of food materials.

Human Digestive System:
The human digestive system can be distinguished into two components:

  • The Alimentary canal
  • Associated organs (Glands)

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Alimentary canal
The Alimentary canal is a hollow tube of about 9 meters length with two openings. An anterior mouth and a posterior Anus. There are several organs in between these regions, which perform specialized functions. The different regions are.

(a) Oral cavity: It is also called the Buccal cavity. It is totally bound by the muscular cheeks. The anterior portion terminates into a pair of fleshy lobes called lips. Internally it is lined by stratified squamous epithelium.

The roof of the buccal cavity is formed by a hard structure called Palate. The anterior part is known as hard palate and the posterior part is called soft palate. The fleshy projection seen at the full end, which prevents the entry of food into the nasal cavity is called Uvula.

The tongue is present on the floor of the buccal cavity. Its upper surface is covered by papillae with taste buds. There are 3 types of papillae present on the tongue namely:

  • Filiform.
  • Fungiform.
  • Circumvallate.

The tongue is attached to the buccal cavity by a soft ligamentous structure called Fremim or Frenulum. Tongue helps in ingestion of food substance, mixing the food with saliva, tasting, and also for speech. Both upper and lower jaw contains teeth. In Humans, teeth are heterodont because 4 different types of teeth are present. They are.

  • Incisors (Cutting teeth)
  • Canines (Tearing teeth)
  • Premolars and
  • Molars (Grinders).

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

The human teeth are Diphyodont because 2 sets of teeth (Milk teeth, and Permanent teeth) are formed during the life time. Human teeth are thecodont because all the teeth are inserted in the sockets. The arrangement of teeth on the jaws is called Dentition. The dental formula This formula indicates half of the upper jaw and half of the lower jaw.

(b) Pharynx : It is a short narrow passage common for both digestive and respiratory systems. It is divisible into anterior nasopharynx, a middle oropharynx and a lower laryngo pharynx. A small cartilage flap called epiglottis is present, which prevents the food from entering the trachea while it is swallowed.

(c) Oesophagus : It is commonly called as food pipe. It is about 25 cm in length. It opens into stomach. It helps in pushing the food to the stomach by the peristaltic contractions of the body wall. The place where Oesophagus enters the diaphragm is called as Oesophageal Hiatus.

(d) Stomach : It is a “J” shaped muscular sac like organ present below the slightly towards the side. It can be distinguished into four regions. They are cardiac, fundus, body, and pylorus. Stomach is the organ of storage and digestion. Pylorus stomach is the digestive organ, and leads info small intestine.

Small intestine :
It is the longest part of the Alimentary canal. It is about 7 meters in length. It can be distinguished into a Duodenum, jejunum and ileum, with a length of 1 meter, 2.5 meter, and 3.5 meter respectively. The small intestine is characterized by the presence of small finger shaped projections called villi, which help in the absorption of food. Duodenum is involved in digestion and absorption whereas jejunum and ileum are involved only in absorption.

Large intestine :
It is about 2 meters long, and broader than small intestine! The large intestine can be distinguished into colon, and Rectum. The large intestine shows ascending colon, transverse colon, descending colon and sigmoid colon.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Rectum is the terminal part, about 20 cm in length. It opens out through the Anus. At the junction of ileum and colon, there is a blind pouch called caecum. A attached to this is a finger shaped structure called vermiform appendix, which is a vestigial organ. Large intestine helps in absorption of water, vitamins and elimination of faeces. Faeces becomes semisolid due to the absorption of water, and also gets coated with mucous.

Salivary Glands :
These are exocrine glands present in buccal cavity. There are 3 pairs of salivary glands opening into the buccal cavity through their respective ducts (Tube like structures). The 3 pairs of salivary glands are:
(1) A pair of parotid glands : Present in front of the ears and opens into the buccal cavity through the cheeks.
(2) A pair of sub-maxillary glands : Present below the lower jaw on either side at the angles of the jaw.
(3) A pair of Sub-lingual glands : Present below the tongue.
All these glands secrete saliva. The saliva contains water, mucin lyzozyme and an enzyme called Salivary amylase or Ptyalin.

Functions of Saliva :
(1) It moistens the dry food and helps in swallowing by a lubricating action.
(2) The salivary amylase or ptyalin acts on starch, and converts it into maltose.
(3) It dissolves soluble substances like salts and sugar and helps in tasting.
(4) It helps in the movement of tongue and lips, by keeping them moist.

Gastric Glands :
These are present in the inner wall of the stomach. There are 3 types of Gastric glands.
(1) Cardiac glands : Present in the cardiac region of the stomach, and they secrete mucus.
(2) Fundic glands : Present in the fimdus region of the stomach. They contain 3 types of cells.
(a) Oxyntic cells or Parietal cells – Secrete HCl.
(b) Chief cells or peptic cells – Secretes pepsinogen, pro rennin and Gastric lipase enzyme.
(c) Mucus cells-Secrete Mucus.
(3) Pyloric glands : Present in the pyloric region of stomach and secrete mucus. All these glands secrete gastric juice. It contains HCl, Mucus, and enzymes like pepsin, rennin, and gastric lipase, the pH of gastric juice is 1.5-2.0.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Functions of Gastric juice :
(1) HCl present in the gastric juice gives acidic PH for the action of enzymes and also kills harmful bacteria.
(2) HCl activates and converts pepsinogen into pepsin, and prorennin into rennin.
(3) Pepsin acts on proteins, and converts them into Peptones, and proteoses.
(4) Rennin acts on the milk protein casein, and converts it into solid casein or curd.

Liver:
It is an accessory gland that is situated outside the Alimentary canal. It is situated just below the diaphragm and attached slightly towards the right side partly covering the stomach. Liver is the largest gland in the human body, weighing about 1.5 Kg (in adults).
It consists of 4 lobes namely:
1. Right lobe (largest lobe).
2. Left lobe (Smallest lobe).
3. Caudate lobe and
4. Quadrate lobe.

Liver is an exocrine gland because it secretes. Its secretion called bile juice is passed through the bile duct. The bile juice is stored in gall blabber.

Bile juice contains bile salts sodium glycocholate and sodium taurocholate, and pigments such as bilirubin, and biliviridin. Each liver lobe is made up of large number of hexagonal shaped units called Hepatic lobules.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Functions :
1. ft is a store house for glycogen, and some vitamins.
2. It secrets bile juice, which helps in emulsification of fats.
3. It is responsible for detoxification of the digested food.
4. It provides proteins like fibrinogen and prothrombin, that are involved in clotting of blood.
5. It is responsible for the maturation of RBC’s.
6. It converts ammonia, the nitrogenous waste, into a less toxic form called urea.
7. Breaking down of worn out RBC’s.
8. It is a site of alcohol metabolism.
9. Kupffer cells helps in phagocytosis.
10. It stores blood, and regulates blood volume in the body.

Pancrease :
It is the second largest gland in human beings. It is a heterocrine gland since it contains both exo and endocrine parts. It is present below the stomach at the region of Duodenum. It is a pale yellowish compound tubular gland and measures about 12.5 cm long, and 2.5 cm in diameter. The exocrine part of pancreas is known as pancreatic acini which secretes pancreatic juice into the duodenum through pancreatic duct (Wrsung duct).  The endocrine part of the pancreas is known as Islets of Langerhans which secretes the hormones called insulin (P cells) and glucagon (cells).

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Functions of Pancreas :
1. Pancreas secretes pancreatic juice. It is rich in bicarbonates, and neutralizes the acidic food.
2. Pancreatic juice contains several enzymes such as Trypsin, Chymotrypsin etc., which help indigestion.
3. The hormones secreted by the islets of Langerhans play an important role in glucose metabolism.
4. Insulin converts excess of blood sugar into glycogen, and glucagon converts stored glycogen into glucose when there is a scarcity of blood sugar.

1st PUC Biology Digestion and Absorption Text Book Questions and Answers

Definition:
The physiological process of breaking up of complex insoluble food materials into simple , soluble substances is called Digestion.
or
Digestion is a catabolic process involving the enzymatic hydrolysis of food materials.
Human Digestive System
The human digestive system can be distinguished into two components:
1. The Alimentary canal
2. Associated organs (Glands)

Alimentary canal
The Alimentary canal is a hollow tube of about 9 meters length with two openings. An anterior mouth and a posterior Anus. There are several organs in between these regions, which perform specialized functions. The different regions are.

(a) Oral cavity: It is also called Buccal cavity. It is totally bound by the muscular cheeks. The anterior portion terminates into a pair of fleshy lobes called lips. Internally it is lined by stratified squamous epithelium.
The roof of the buccal cavity is formed by a hard structure called Palate. The anterior part is known as hard palate and the posterior part is called soft palate. The fleshy projection seen at the full end, which prevents the entry of food into the nasal cavity is called Uvula.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

The tongue is present on the floor of the buccal cavity. Its upper surface is covered by papillae with taste buds. There are 3 types of papillae present on the tongue namely:
(1) Filiform.
(2) Fungiform.
(3) Circumvallate.

The tongue is attached to the buccal cavity by a soft ligamentous structure called Fremim or Frenulum. Tongue helps in ingestion of food substance, mixing the food with saliva, tasting, and also for speech. Both upper and lower jaw contain teeth. In Humans, teeth are heterodont because 4 different types of teeth are present. They are.
(1) Incisors (Cutting teeth)
(2) Canines (Tearing teeth)
(3) Premolars and
(4) Molars (Grinders).

(a) The human teeth are Diphyodont because 2 sets of teeth (Milk teeth, and Permanent teeth) are formed during the life time. Human teeth are thecodont because all the teeth are inserted in the sockets. The arrangement of teeth on the jaws is called Dentition. The dental formula
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 3
This formula indicates half of the upper jaw and half of the lower jaw.

(b) Pharynx : It is a short narrow passage common for both digestive and respiratory systems. It is divisible into anterior nasopharynx, a middle oropharynx and a lower laryngo pharynx. A small cartilage flap called epiglottis is present, which prevents the food from entering the trachea while it is swallowed.

(c) Oesophagus : It is commonly called as food pipe. It is about 25 cm in length. It opens into stomach. It helps in pushing the food to the stomach by the peristaltic contractions of the body wall. The place where Oesophagus enters the diaphragm is called as Oesophageal Hiatus.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

(d) Stomach : It is a “J” shaped muscular sac like organ present below the slightly towards the side. It can be distinguished into four regions. They are cardiac, fundus, body, and pylorus. Stomach is the organ of storage and digestion. Pylorus stomach is the digestive organ, and leads info small intestine.

Small intestine :
It is the longest part of the Alimentary canal. It is about 7 meters in length. It can be distinguished into a Duodenum, jejunum and ileum, with a length of 1 meter, 2.5 meter, and 3.5 meter respectively. The small intestine is characterized by the presence of small finger shaped projections called villi, which help in the absorption of food. Duodenum is involved in digestion and absorption whereas the jejunum and ileum are involved only in absorption.

Large intestine :
It is about 2 meters long, and broader than small intestine! The large intestine can be distinguished into colon, and Rectum. The large intestine shows ascending colon, transverse colon, descending colon and sigmoid colon.

Rectum is the terminal part, about 20 cm in length. It opens out through the Anus.

At the junction of ileum and colon, there is a blind pouch called caecum. A attached to this is a finger shaped structure called vermiform appendix, which is a vestigial organ. Large intestine helps in absorption of water, vitamins and elimination of faeces. Faeces becomes semisolid due to the absorption of water, and also gets coated with mucous.

Salivary Glands :
These are exocrine glands present in buccal cavity. There are 3 pairs of salivary glands opening into the buccal cavity through their respective ducts (Tube like structures). The 3 pairs of salivary glands are:

  • A pair of parotid glands : Present in front of the ears and opens into the buccal cavity through the cheeks.
  • A pair of sub-maxillary glands : Present below the lower jaw on either side at the angles of the jaw.
  • A pair of Sub-lingual glands : Present below the tongue.

All these glands secrete saliva. The saliva contains water, mucin lyzozyme and an enzyme called Salivary amylase or Ptyalin.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Functions of Saliva :
(1) It moistens the dry food and helps in swallowing by a lubricating action.
(2) The salivary amylase or ptyalin acts on starch, and converts it into maltose.
(3) It dissolves soluble substances like salts and sugar and helps in tasting.
(4) It helps in the movement of tongue and lips, by keeping them moist.

Gastric Glands :
These are present in the inner wall of the stomach. There are 3 types of Gastric glands.
(1) Cardiac glands : Present in the cardiac region of the stomach, and they secrete mucus.
(2) Fundic glands : Present in the famous region of the stomach. They contain 3 types of cells.
(a) Oxyntic cells or Parietal cells – Secrete HCl.
(b) Chief cells or peptic cells – Secretes pepsinogen, pro rennin and Gastric lipase enzyme.
(c) Mucus cells-Secrete Mucus.
(3) Pyloric glands : Present in the pyloric region of stomach and secrete mucus. All these glands secrete gastric juice. It contains HCl, Mucus, and enzymes like pepsin, rennin, and gastric lipase, the pH of gastric juice is 1.5-2.0.

Functions of Gastric juice :
(1) HCl present in the gastric juice gives acidic PH for the action of enzymes and also kills harmful bacteria.
(2) HCl activates and converts pepsinogen into pepsin, and prorennin into rennin.
(3) Pepsin acts on proteins, and converts them into Peptones, and proteoses.
(4) Rennin acts on the milk protein casein, and converts it into solid casein or curd.

Liver:
It is an accessory gland that is situated outside the Alimentary canal. It is situated just below the diaphragm and attached slightly towards the right side partly covering the stomach. Liver is the largest gland in the human body, weighing about 1.5 Kg (in adults).
It consists of 4 lobes namely:
1. Right lobe (largest lobe).
2. Left lobe (Smallest lobe).
3. Caudate lobe and
4. Quadrate lobe.

Liver is an exocrine gland because it secretes. Its secretion called bile juice is passed through the bile duct. The bile juice is stored in gall blabber.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Bile juice contains bile salts sodium glycocholate and sodium taurocholate, and pigments such as bilirubin, and biliviridin. Each liver lobe is made up of large number of hexagonal shaped units called Hepatic lobules.

Functions :
1. ft is a store house for glycogen, and some vitamins.
2. It secrets bile juice, which helps in emulsification of fats.
3. It is responsible for detoxification of the digested food.
4. It provides proteins like fibrinogen and prothrombin, that are involved in clotting of blood.
5. It is responsible for the maturation of RBC’s.
6. It converts ammonia, the nitrogenous waste, into a less toxic form called urea.
7. Breaking down of worn out RBC’s.
8. It is a site of alcohol metabolism.
9. Kupffer cells helps in phagocytosis.
10. It stores blood, and regulates blood volume in the body.

Pancrease :
It is the second largest gland in human beings. It is a heterocrine gland since it contains both exo and endocrine parts. It is present below the stomach at the region of Duodenum. It is a pale yellowish compound tubular gland and measures about 12.5 cm long, and 2.5 cm in diameter. The exocrine part of pancreas is known as pancreatic acini which secretes pancreatic juice into the duodenum through pancreatic duct (Wrsung duct).
The endocrine part of the pancreas is known as Islets of Langerhans which secretes the hormones called insulin (P cells) and glucagon (a cells).

Functions of Pancreas :
1. Pancreas secretes pancreatic juice. It is rich in bicarbonates, and neutralizes the acidic food.
2. Pancreatic juice contains several enzymes stich as Trypsin, Chymotrypsin etc., which help in digestion.
3. The hormones secreted by the islets of Langerhans play an important role in glucose metabolism.
4. Insulin converts excess of blood sugar into glycogen, and glucagon converts stored glycogen into glucose when there is a scarcity of blood sugar.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Intestinal Glands :
These are present in the inner mucosa of small intestine. There are 4 types of intestinal glands, they are:-
1. Glands of crypts of lieberkuhn.
2. Payer’s glands.
3. Brunner’s glands.
4. Solitary glands.

Out of these glands, crypts of lieberkuhn secretes intestinal juice (Succus entericus), While others secrete an alkaline secretion which protects the intestinal lining from bacterial infection. Components of Food (Concept of Balanced Diet):

A balanced diet is one which contains the right proportion of the seven nutrients namely carbohydrates, fats, proteins, vitamins, minerals, water, and roughage (Fibrous component) required to maintain good health.
Carbohydrates and lipids (fats) provide energy for the body. Proteins are required for growth, maintenance and repair of worn-out tissues. Water, minerals, and vitamins are essential for maintaining normal metabolism.

The correct and recommended proportion of balanced diet is represented as follows. Carbohydrates – 64%, Proteins – 14%, Lipids-21%, Vitamins, and minerals – 1%.
In addition, large amount of roughage consisting of mainly fibrous cellulose is also important.

Process of Digestion :
During this process, the complex food molecules such as proteins, carbohydrates, and lipids are converted into smaller molecules such as amino acid, monosaccharide, fatty acids, and glycerol respectively.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Digestion in Buccal Cavity :
As soon as the food enters into the buccal cavity, both mechanical and chemical digestion takes place. Mechanical digestion is brought about by the cutting and chewing action of the teeth. During this process the complex food molecules are converted into smaller molecules. In the mean time, saliva is secreted and mixes with the food.

Role of Saliva :
Saliva is an alkaline digestive juice containing water, mucin, lysozyme, and an enzyme salivary amylase (Ptyalin). Water dissolves the soluble food substances, mucin lubricates the food, and ptyalin acts on the starch part of food and finally converts it into maltose.
\(\text { Starch } \frac{\text { Ptyalin,pH6:7 }}{\longrightarrow} \text { Soluble starch } \stackrel{+\mathrm{H}_{2} \mathrm{O}}{\longrightarrow} \text { Dextrin } \stackrel{+\mathrm{H}_{2} \mathrm{O}}{\longrightarrow} \text { Maltose }\)

The process of grinding the food with the help of the teeth is called as mastication. After the partial digestion of food in the buccal cavity, the food is shaped into a spherical mass called Bolus. The bolus is swallowed into the stomach through the Oesophagus.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Digestion in Stomach :
As soon as the food Bolus enters the stomach, the gastric mucosa secretes a hormone called gastrin. It stimulates the gastric glands to secrete gastric juice.

Role of Gastric juice :
Gastric juice contains HCl, mucus, and enzymes like pepsin, Rennin, and Gastric lipase. HCl gives acidic pH, dissolves insoluble minerals, and fibrous proteins, and converts inactive form of pepsinogen, and prorennin into active form of pepsin, and rennin respectively.

Role of Pepsin :
It is secreted in an inactive form called Pepsinogen. It is converted into active form of Pepsin by HCl.
\(\text { Pepsinogen } \stackrel{\mathrm{HCl}}{\longrightarrow} \text { Pepsin }\)
Pepsin acts on proteins, and converts them into peptones, proteoses and polypeptides.
\(\text { Proteins } \stackrel{\text { pepsin }^{\circ}}{\longrightarrow} \text { Peptones }+\text { Proteoses }+\text { Polypeptides }\)

Role of Rennin :
It is secreted in an inactive form called prorennin. It is activated into rennin by HCl.
\(\text { Prorennin } \stackrel{\mathrm{HCl}}{\longrightarrow} \text { Rennin }\)

Rennin acts on the milk protein casein, and converts it into Para casein.
\(\text { Casein } \stackrel{\text { Rennin }}{\longrightarrow} \text { Para casein }\)

Para casein combines with calcium ions to form solid casein or curd.
Para casein +Ca2+→ Calcium paracaseinate (Solid Casein).

Calcium paracaseinate is acted upon by pepsin, and converted into proteoses, peptones and polypeptides
\(\text { Calcium paracaseinate } \stackrel{\text { pepsin }}{\longrightarrow} \text { Peptones + Proteoses + Polypeptides }\)

Role of Gastric lipase :
It is inactive in the adult stomach because of more acidic pH, but in children it acts on butter fat. After the partial digestion of food in the stomach, it is converted into semisolid substance known as Chyme.

Digestion in Small Intestine:
When partially digested acidic chyme enters into the duodenum of small intestine, the intestinal mucosa secretes 4 types of gastro intestinal hormones.
1. Enterocrinin : Stimulates the secretion of intestinal juice from intestinal glands.
2. Secretin : Stimulates the secretion of pancreatic juice.
3. Cholecystokinin (CCK): Stimulates the contraction of gall bladder to secrete bile juice
4. Enterogastrin : Inhibits the secretion of gastric juice by gastric glands.

Role of Bile juice :
Bile juice is secreted by the hepatic cells of liver, and stored in the gall bladder. It is released into the duodenum through the bile duct. Bile juice doesn’t contain any digestive enzymes. But it contains the digestive components in the form of bile salts Sodium Glycocholate, and Sodium taurocholate, Bile salts emulsify the fats by lowering their surface tension, and convert them into numerous tiny droplets. Bile is rich in sodium bicarbonate; hence it neutralizes the acidic chyme. It also helps in absorption of fat soluble vitamin K.
\(\text { Fats } \stackrel{\text { Bile }}{\longrightarrow} \text { Emulsified fats. }\)

Role of Pancreatic juice :
The Pancreatic juice is secreted from acinar cells (Exocrine part) of the pancreas. It contains the following digestive enzymes namely Trypsin, Carboxypeptidase, Chymotrypsin, Amylopsin (Pancreatic amylase), Steapsin etc.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Trypsin :
It is secreted in an inactive form called Trysinogen. It is activated by non-digestive intestinal enzyme called Enterokinase. Trypsin acts on whole proteins or semi digested, ones and convert them into polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 21

Chymotrypsin :
It is secreted in an inactive form called chymotrypsinogen. It is activated by an enzyme called trypsin. Chymotrypsinogen acts on peptones, proteoses, and convert them into polypeptides.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 22

Carboxypeptidase :
It is secreted in an inactive form called procarboxypeptidase. It is activated by an enzyme called trypsin. Carboxypeptidase acts on whole are semi digested proteins, and hydrolyzes carboxyl terminal bonds. .The products are poly peptides, dipeptides, and amino acids.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 23

Amylopsin :
It is also known as pancreatic amylase. It acts on starch and glycogen, and converts them into maltose.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 24

Steapsin :
It is also known as pancreatic lipase. It acts on emulsified fats, and convert them into fatty acids, and glycerol.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Nucleic acids:
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 26

Role of Intestinal Juice :
Intestinal juice is secreted by the intestinal glands. It is also called succus entericus. It contains enzymes like- Enterokinase, amino peptidase and dipeptidase, Sucrase, Maltase, Lactase, Phospholipase, and nuclease.

Nucleases are of three types:
1. Nucleotidase.
2. Phosphotase.
3. Nucleosidase.

Enterokinase:
It is a non digestive intestinal enzyme and acts as an activator. It activates the inactive form trypsinogen of pancreatic juice into trypsin.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 27

Amino peptidase and Dipeptidase :
They generally act on fragments of protein, and not on whole proteins hence, they are commonly called peptidases.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 28

Sucrase:
It converts sucrose into glucose and fructose.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 29

Maltase :
It converts maltose into glucose and glucose.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 30

Lactase :
It converts Lactose into Glucose and Galactose.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 31

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Phospholipase:
If acts on Phospholipids and converts them into phosphoric acid, fatty acid and glycerol. Phospholipids 1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 32

Nucleases :
(a) Nucleotidase : It acts on nucleic acids and converts them into nucleotides.
DNA on Nuclear Tides.

(b) Phosphotase : It acts on Nucleotides, and converts them into Inorganic Phosphates
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 33

(c) Nucleosidase : It acts on Nucleosides and converts them into Nitrogen base and pentose Sugar.
1st PUC Biology Question Bank Chapter 16 Digestion and Absorption 34

Thus the intestinal juice plays an important role in the digestion of proteins’; carbohydrates, lipids and nucleic acids. As a result, the food in the small intestine is converted into a watery emulsion called Chyle.
After the digestion of all these components in the small intestine, the nutrient food substances such as amino acids, monosaccharides, fatty acids and glycerol are absorbed by the villi present in the wall of the small intestine, by active and passive mechanisms. After the absorption, the undigested food and the cellulose part of food enters into large intestine.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Digestion in large intestine [colon]:
There is not much digestion carried out in the large intestine. The intestiral contents are decomposed by symbiotic bacteria (E.coli). The cellulose part of the diet provides roughage for the movement of intestinal content. The wall of the large intestine also absorbs water and electrolytes.

Absorption of digestive food:
Small intestine is involved in absorption of major part of the nutrients through diffusion, osmosis, facilitated diffusion and active transport.

Carbohydrates are absorbed in the form of monosaccharides, lipids are mainly absorbed in the form of fatty acids, and monoglycerides proteins are absorbed in the form of amino acids.

Assimilation:
The amino acids and sugars are transported to the liver, the through hepatic portal vein. Amino acids are used for synthesis of cell organelles, enzymes and hormones. Glucose is utilised by the cells for obtaining energy by its breakdown. Excess glucose is converted into glycogen, and stored in the liver and muscles. A part of the excess glucose is converted into fats for storage in the adipose tissue. Ribose, and deoxyribose sugars are utilised for synthesis of ATP, RNA and DNA.

Regulation Of Digestion:
The functioning of the digestive system is under the control of Nervous system and hormones.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Neural Control:
1. Sight, smell or taste of food can stimulate the secretion of saliva.
2. Neural signals control the gastric and intestinal secretions, and hormones.
3. Muscular activities of the different parts of the alimentary canal are regulated by nerves.

Mormonal Control:
The following hormones control the activities of alimentary canal:
(a) Gastric – controls secretion of gastric juice.
(b) Secreting – stimulates the secretion of water, and bicarbonate ions
(c) Chorley – stimulates pancreas to release pancreatic juice and gall bladder to release bile juice.

Digestive Disorers :
Jaundice [Icterus]:
It is the most common digestive disorder. Jaundice relates to the yellow appearance of skin, urine, nails and cornea of the eye due to an increased Bilirubin pigment (Bile pigment).

Jaundice is of three types:
1. Haemolytic Jaundice or Neonatal Jaundice or Prehepatic Jaundice : It is commonly found in newly born babies up to one week of age. It is due to the excessive haemolysis (Destruction of RBC’s).

2. Infective or Hepatocellular Jaundice : It is due to the infection of hepatitis virus of the liver. So, the liver becomes unable to process Bilirubin. It results in heavy accumulation of Bilirubin which leads to Hepatocellular Jaundice.

3. Obstructive Jaundice or Extra Hepatic jaundice : It occurs due to the obstruction in the Bile duct. The obstruction of Bile duct is due to gallstone formation. The bile duct is thus blocked, and bile juice cannot enter into duodenum.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Causes:
1. Liver damage due to viral infection, and consumption of alcohol.
2. Increased Bilirubin pigment in the body.
3. Excessive haemolysis.
4. Blockage of bile duct due to gallstone.
5. Presence of tumors in the bile duct.

Effects:
1. Yellow colouration of the skin, eyes and urine.
2. Fever, loss of appetite, nausea, vomiting and headache.
3. Infective jaundice leads to bleeding, and shrinkage of liver [Cirrhosis]
4. Unconsciousness and finally it may lead to death.

Prevention:
It can be prevented by avoiding the consumption of alcohol, and also by avoiding the consumption of contaminated food and water.
Treatment :
1. Vaccines, and anti-viral drugs are used against infective jaundice.
2. Obstructive jaundice can be treated by surgery.

Hepatitis :
Hepatitis is the inflammation of the liver. Here the cells are either damaged or destroyed. Types of Hepatitis
1. Viral hepatiti
2. Toxic hepatitis
3. Alcoholic hepatitis Viral hepatitis:
Occurs due to the infection of different strains of viruses namely A, B, C, D, and E.
Of these, Hepatitis A virus (HAV) is a DNA virus. Its infection is through contamination of food, and water.
Hepatitis B virus (HBV) is a RNA virus, and its transmission is through contact body fluids such as sexual contact, Blood transfusion, use of improperly sterilized ‘ surgical instruments, needles etc.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Toxic hepatitis:
It is caused by the toxic effect of drugs on the liver. Some of the drugs known to cause toxicity in susceptible individuals are Paracetamol, Aspirin, heavy metals, mushroom poisoning, etc.
Alcoholic hepatitis:
It is due to excessive consumption of alcohol over a period of time.

Symptoms:
The most common symptoms are : Loss of appetite, fatigue (tiredness), mild fever, muscle, and joint aches.
Prevention and Treatment:
1. Consumption of boiled water, and cooked food.
2. Using anti bacterial, and antiviral drugs as prescribed by a doctor.
3. Undergoing vaccination for Hepatitis – B.
4. Avoiding sexual contact with infected persons, and blood transfusion from infected persons.
5. Using disposable, and sterilized needles.

Vomiting:
Vomiting is a forceful expulsion of part or all the contents of the stomach through mouth. It is due to reverse peristalsis of stomach and oesophagus.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Causes:
1. Harmful food substances, certain drugs or chemicals.
2. Head injury.
3. Irritation of stomach and duodenum.
4. Morning sickness seen during early pregnancy.
5. Emotional factors like nauseating sights and odours may be.

Effects
Excessive vomiting can lead to loss of salts, and fluids from the body causing dehydration and low BP.

Diarrhoea :
It is a condition where the watery faeces move through the large intestine uncontrollably and rapidly.

Causes:
1. Viral, bacterial or protozoan infection.
2. Inflammation of colon.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Effects
Diarrhoea results in dehydration, and electrolyte imbalance. Severe diarrhoea is dangerous.

Constipation :
It is improper, infrequent or difficult defaecation. It arises when the contents are retained in the large intestine for a longer duration than the normal. More water is absorbed from the feces making it hard and dry.

Causes:
1. Ignoring the urge to defecate.
2. Decreased mobility in colon due to low bulk diet or aging.
3. Blockage due to tumour in the colon.
4. Injury to nerve pathway which relaxes the muscles for defaecation.

1st PUC Biology Question Bank Chapter 16 Digestion and Absorption

Effects:
It causes abdominal discomfort, dull headache, loss of appetite and mental depression. The symptoms may disappear after defaecation.

Indigestion.
Inability to digest food is called indigestion. Symptoms include feeling of fullness in the stomach, discomfort in the upper abdomen, burping, and heartburn.

Causes:
1. Insufficient production of digestive enzymes.
2. Overeating or eating fatty or fried foods.
3. Less likely causes include gallstones, ulcer of stomach or duodenum.
Loss of appetite and vomiting.

Protein Energy Malnutrition (Pem) :
Decreased intake of proteins in the food results in PEM. Clinically two types of PEM are recognised namely. Kwashiorkor, and Marasmus.

Kwashiorkor :
In this disease protein intake is inadequate but the calorie requirement of the body is met. It results in protein malnutrition characterised by edema of the abdomen, decreased blood pressure, loss of appetite, enlarged liver, excessive pigmentation of the skin and mental retardness.

Marasmus :
This disease is due to inadequate intake of proteins, and calories. It is characterised by low weight, wasting of muscles, dry skin and a thin body.

1st PUC Biology Question Bank with Answers