TEXTBOOK ANSWERS AND SOLUTIONS Chapter-16-Digestion and Absorption CBSE-CLASS-XI-BIOLOGY

1) Choose the correct answer among the
following:

a) Gastric juice contains

I) pepsin, lipase, rennin

ii) Trypsin, lipase, rennin

iii) Trypsin, pepsin, lipase

iv) Trypsin, pepsin, rennin

An- Pepsin, lipase, rennin

b) Succuss entericus is the name given to

I) a junction between ileum &
large Intestine

ii) Intestinal juice

iii) Swelling in the gut

iv) Appendix

Ans. – ii) Intestinal juice

2) Match the following

Column-I Column-II

A) Billirubin & Biliverdin I) Parotid

b) Hydrolysis of starch ii) Bill

c) Digestion of fat iii) Lipases

d) Salivary gland IV) Amylases

An- {a
– iii} {c – iii}

{b – Iv) {d
– i)

3)
A) Why are villi present in the intestine & not in stomach?

To increase the surface area of the
intestine for the efficient absorption of digested food villi are present in
intestine.

b) How does pepsinogen changes into its
active form?

Pepsin (inactive form) is first changed by
HCL into active enzyme pepsin. Then through autocatalysis more of pepsinogens
get activated to pepsin.

c) What are the basic layers of the wall of
the alimentary cannot?

The four main concentrate coats of
alimentary canals are

I) visceral peritoneum

ii) Muscular coat

iii) Sub – mucosa

iv) Mucosa

d) How does bile help in the digestion of
fats?

Fats are broken down by lipase with
the help of bill into di- and monoglycerydes

Fats is passes Diglycerides – monoglycerides

4)
Give the teeth formula of human beings

5)
Describe the digestive role of chymotrypsin. Which two others digestive enzymes
of the same category are secreted by its source gland?

Chymotrypsin converts; proteins into
large peptides, Trypsin & Elastase
are two other digestive enzymes of the same category are secreted by its source
gland.

6)
How are polysaccharides &
disaccharides digested?

Digestions of polysaccharides

Action of saliva starch

maltose
+ Isomaltose + alpha dextrin

Action of Pancreatic Juice

Starch

Maltose
+ Isomaltose + alpha-Dextrin

Digestion of Disaccharides

Action of Intestinal Juice

Maltose Maltose
Glucose + Glucose

Isomaltose Isomaltose Glucose + Glucose

Sucrose sucrase Glucose + fructose

Lactose lactase Glucose +
Galactose

Dextrin

Dixtrinose
Glucose

7)
What would happen if HCL is not secreted
in the stomach?

Pepsinogen (proenzyme) & prorenin
(pro-enzyme) will not be concentrated into pepsin & rein respectively. Hcl
provides acidic medium so that the enzyme can act on food in stomach. Hcl kills
bacteria & other harmful organism that may be present along with food.

8) Explain the term thecodont & diphyodont?

In human beings, teeth are embedded in
pits, the sockets of the jaw bones. Such teeth are called thecodont.

The teeth that appear in two sets i.e. milk
teeth which are latter replaced by permanent teeth. This condition is called
diphycodont.

9)
Name different types of teeth their no
in an adult human.

Upper jaw lower
jaw upper jaw lower
jaw

Incisors
4
4       Premolars
       4          4

Canines
2 2 molars
6 6

10)
State the role of pancreatic juice in
digestion of proteins

Action of pancreatic juice – pancreatic
juice contains pro-enzymes

Trypsinogen, chymotrypsinogen and
procarboxypeptase

And enzyme elastase

Tripsinogen

trypnin

(Proenzyme)

Chymotrypsin Trypsin Carboxypeptidase

(Pro-enzyme)

Pretium 1 peptones & proteases are
acted upon as given below

Proteins Trypsin Dipeptides

Peptones Chymotrypsin Dipeptides

Proteases Carboxypeptidases Dipeptides

Pro-elastase Typsin Elastase

(Pro-enzyme)

11)
Describe the process of digestion of protein in stomach.

The digestion of proteins in stomach is
caused by the actions of gastric juice. The stomach contains Hcl, proenzymes –
pepsinogen & prorenin. Hcl mainly maintains a strong ph balance of body
about 1.5 to 2.5 in the stomach. They kill the bacteria entering with food .hcl
converts pepsinogen and prorenin into pepsin and rennin. Once pepsin is formed
it changes pepsinogen into pepsin. Such activation is called autocatalytic
reaction. Pepsin and rennin are absent in invertebrates’. Gastric juice is
thoroughly mixed with food until it becomes a semi fluid mass called chyme

12)
Bite juice contains no digestive enzyme
yes it is important for digestion why?

Bite contains no digestive enzyme yet it is
important for digestion. Why?

1.
Neutrilises hcl

2.
Emulsification

3.
Activate lipase

4.
Absorption of fats and fat soluble vitamins

13)
How does butter in your food get digested
& absorbed in the body?

Term lipase is usually used as fat
digestive enzyme

Saliva contains no lipase. The stomach also
lacks much fat emulsifying agent. However the gastric juice contains small amount
of gastric lipase active some fat into mono glycerides & fatty acids. That
is largely digested on small intestine. But bile break down fat droplets into
may small ones by reducing the surface areas of fat droplets. This process is
called emulsification. & increase lipase action on fat. Pancreatic lipase
to the principal enzyme for the digestion of fat. In addition intestinal lipase
in also helpful in digestion of fat

Fat
Bite emulsified

(Triglyceride)

14)
Discuss the main steps in the digestion
of proteins as the food posses through different parts of canal.

Digestion of proteins occurs by

1) Digestion in the stomach

2) Digestion in the small intestine.

1) Action of pancreatic juice

2) Action of intestine Juice

15)
What are the functions of liver?

1) Production of bill ii) Deamination

iii) Excretion IV) Neutralization of Hcl.

v) Lymph formatives.

vi) Destruction of R.B.C

vii) Secretions of enzymes

viii) Glycogenesis.