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NCERT Solutions for Class 12 Biology Chapter 10
Microbes in Human Welfare Class 12
Chapter 10 Microbes in Human Welfare Exercise Solutions
Exercise : Solutions of Questions on Page Number : 189
Q1 :
Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you
have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes
under a microscope, which sample would you carry and why?
Answer :
Curd can be used as a sample for the study of microbes. Curd contains numerous lactic acid bacteria (LAB)
orLactobacillus. These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd contains
millions of bacteria, which can be easily observed under a microscope.
Q2 :
Give examples to prove that microbes release gases during metabolism.
Answer :
The examples of bacteria that release gases during metabolism are:
(a) Bacteria and fungi carry out the process of fermentation and during this process, they release carbon dioxide.
Fermentation is the process of converting a complex organic substance into a simpler substance with the action of
bacteria or yeast. Fermentation of sugar produces alcohol with the release of carbon dioxide and very little energy.
(b) The dough used for making idli and dosa gives a puffed appearance. This is because of the action of bacteria
which releases carbon dioxide. This CO2 released from the dough gets trapped in the dough, thereby giving it a
puffed appearance.
Q3 :
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer :
Lactic acid bacteria can be found in curd. It is this bacterium that promotes the formation of milk into curd. The
bacterium multiplies and increases its number, which converts the milk into curd. They also increase the content of
vitamin B12 in curd.
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Lactic acid bacteria are also found in our stomach where it keeps a check on the disease-causing micro-organisms.
Q4 :
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve
use of microbes.
Answer :
(a) Wheat:
Product: Bread, cake, etc.
2. Rice:
Product: Idli, dosa
2. Bengal gram:
Product: Dhokla, Khandvi
Q5 :
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer :
Several micro-organisms are used for preparing medicines. Antibiotics are medicines produced by certain micro-
organisms to kill other disease-causing micro-organisms. These medicines are commonly obtained from bacteria and
fungi. They either kill or stop the growth of disease-causing micro-organisms. Streptomycin, tetracycline, and
penicillin are common antibiotics. Penicillium notatum produces chemical penicillin, which checks the growth
of staphylococci bacteria in the body. Antibiotics are designed to destroy bacteria by weakening their cell walls. As a
result of this weakening, certain immune cells such as the white blood cells enter the bacterial cell and cause cell
lysis. Cell lysis is the process of destroying cells such as blood cells and bacteria.
Q6 :
Name any two species of fungus, which are used in the production of the antibiotics.
Answer :
Antibiotics are medicines that are produced by certain micro-organisms to kill other disease-causing micro-
organisms. These medicines are commonly obtained from bacteria and fungi.
The species of fungus used in the production of antibiotics are:
Antibiotic Fungus source
www.ncrtsolutions.in
NCERT Solutions for Class 12 Biology Chapter 10
Microbes in Human Welfare Class 12
Chapter 10 Microbes in Human Welfare Exercise Solutions
Exercise : Solutions of Questions on Page Number : 189
Q1 :
Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you
have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes
under a microscope, which sample would you carry and why?
Answer :
Curd can be used as a sample for the study of microbes. Curd contains numerous lactic acid bacteria (LAB)
orLactobacillus. These bacteria produce acids that coagulate and digest milk proteins. A small drop of curd contains
millions of bacteria, which can be easily observed under a microscope.
Q2 :
Give examples to prove that microbes release gases during metabolism.
Answer :
The examples of bacteria that release gases during metabolism are:
(a) Bacteria and fungi carry out the process of fermentation and during this process, they release carbon dioxide.
Fermentation is the process of converting a complex organic substance into a simpler substance with the action of
bacteria or yeast. Fermentation of sugar produces alcohol with the release of carbon dioxide and very little energy.
(b) The dough used for making idli and dosa gives a puffed appearance. This is because of the action of bacteria
which releases carbon dioxide. This CO2 released from the dough gets trapped in the dough, thereby giving it a
puffed appearance.
Q3 :
In which food would you find lactic acid bacteria? Mention some of their useful applications.
Answer :
Lactic acid bacteria can be found in curd. It is this bacterium that promotes the formation of milk into curd. The
bacterium multiplies and increases its number, which converts the milk into curd. They also increase the content of
vitamin B12 in curd.
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, www.ncrtsolutions.in
Lactic acid bacteria are also found in our stomach where it keeps a check on the disease-causing micro-organisms.
Q4 :
Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve
use of microbes.
Answer :
(a) Wheat:
Product: Bread, cake, etc.
2. Rice:
Product: Idli, dosa
2. Bengal gram:
Product: Dhokla, Khandvi
Q5 :
In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
Answer :
Several micro-organisms are used for preparing medicines. Antibiotics are medicines produced by certain micro-
organisms to kill other disease-causing micro-organisms. These medicines are commonly obtained from bacteria and
fungi. They either kill or stop the growth of disease-causing micro-organisms. Streptomycin, tetracycline, and
penicillin are common antibiotics. Penicillium notatum produces chemical penicillin, which checks the growth
of staphylococci bacteria in the body. Antibiotics are designed to destroy bacteria by weakening their cell walls. As a
result of this weakening, certain immune cells such as the white blood cells enter the bacterial cell and cause cell
lysis. Cell lysis is the process of destroying cells such as blood cells and bacteria.
Q6 :
Name any two species of fungus, which are used in the production of the antibiotics.
Answer :
Antibiotics are medicines that are produced by certain micro-organisms to kill other disease-causing micro-
organisms. These medicines are commonly obtained from bacteria and fungi.
The species of fungus used in the production of antibiotics are:
Antibiotic Fungus source
www.ncrtsolutions.in
