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NCERT Exemplar · Class 12 · Biology

Chapter 10: Microbes in Human Welfare

Practice each question, then open the answer or worked solution.

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Multiple Choice Questions

18 questions
Q1Multiple choice

The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is 

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Correct option: C
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Ans: Option (c) is the answer. Lactic acid bacteria are used to transform milk into curd. Lactic acid bacteria and casein combine to produce this reaction. The bacteria employ enzymes to manufacture energy from ATP during this process, which also boosts the nutritional value of the food by raising vitamin B12 concentration.


Q2Multiple choice

Wastewater treatment generates a large quantity of sludge, which can be treated by:

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Correct option: A
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Ans: Option (a) is the answer. During secondary treatment, a large amount of activated sludge is generated, which is utilized as an inoculum. A small portion of this sludge is piped back to the massive aeration tanks, while the rest is treated anaerobically using anaerobic sludge digesters. Bacteria generate a combination of gases known as biogas during this digestion.


Q3Multiple choice

Methanogenic bacteria are not found in:

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Correct option: D
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Worked solution

Ans: Option (d) is the answer. Inactivated sludge, methanogenic bacteria (bacteria that create methane) are not detected. Microorganisms that produce methane are anaerobic bacteria. Aerobic bacteria that proliferate quickly are seen in activated sludge microorganisms.


Q4Written answer

Match the following list of bacteria and their commercially important products:

Bacterium

Product

A. Aspergillus niger

i. Lactic acid

B. Acetobacter acetic

ii. Butyric acid

C. Clostridium bretylium

iii. Acetic acid

D. Lactobacillus

iv. Citric acid


Choose the correct match:

a. A-ii, B-iii, C-iv, D-i

b. A-ii, B-iv, C-iii, D-i

c. A-iv, B-iii, C-ii, D-i

d. A-iv, B-i, C-iii, D-ii

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Worked solution

Ans:  Option (c) is the answer.

Bacterium 

Product

(i) Aspergillus niger

(D) Citric acid 

(ii) Acetobacter aceti

(C) Acetic acid

(iii) Clostridium butylicum

(B) Butyric acid

(iv) Lactobacillus

(A) Lactic acid


Q5Written answer

Match the following list of bioactive substances and their roles:

Bioactive Substance

Role

A. Statin

i. Removal of oil stains

B. Cyclosporin A

ii. Removal of clots from blood vessels

C. Streptokinase

iii. Lowering of blood cholesterol

D. Lipase

iv. Immuno-suppressive agent

Choose the correct match:

a. A-ii, B-iii, C-i, D-iv

b. A-iv, B-ii, C-i, D-iii

c. A-iv, B-i, C-ii, D-iii

d. A-iii, B-iv, C-ii, D-i

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Worked solution

Ans: Option (d) is the answer

Bioactive Substance

Role

(i) Statin

(C) Statins produced by yeast Monascus purpureus and used as a blood cholesterol lowering agents.

(ii) Cyclosporin A

(D) It is used as an immunosuppressive agents produced by fungus Trichoderma polysporum.

(iii) Streptokinase

(B) It is produced by bacteria Streptococcus and used as clot bluster for removing clots from blood vessels of patients which undergo myocardial infarction leading to heart attack.

(iv) Lipase

(A) used in detergent formulations and remove oil stains from the laundry.


Q6Multiple choice

The primary treatment of wastewater involves the removal of:

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Correct option: B
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Worked solution

Ans: Option (b) is the answer. Filtration and sedimentation are used in the initial treatment to physically remove particles from the sewage. These are removed first by sequential filtering, which eliminates floating debris, and then by sedimentation, which removes grit.


Q7Multiple choice

BOD of wastewater is estimated by measuring the amount of:

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Correct option: D
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Worked solution

Ans: Option (d) is the answer. The quantity of oxygen consumed when all the organic matter in one litre is oxidized by bacteria is known as biological oxygen demand (BOD). Thus, the quantity of oxygen used is used to calculate the BOD of wastewater.


Q8Multiple choice

Which one of the following alcoholic drinks are produced without distillation?

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Correct option: A
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Ans: Option (a) is the answer. Wine is an alcoholic drink produced without distillation whereas whisky, rum, and brandy are produced by the distillation of the fermented broth. The alcoholic drinks are formed either by distillation or without distillation depending on the type of raw material used for fermentation.


Q9Multiple choice

The technology of biogas production from cow dung was developed in India largely due to the efforts of:

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Correct option: C
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Ans: Option (c) is the answer. The technology of biogas production from cow dung was developed in India largely due to the efforts of the Indian Agricultural Research Institute (IARI) and Khadi & Village Industries Commission (KVIC).


Q10Multiple choice

The free-living fungus Trichoderma can be used for:

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Correct option: B
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Worked solution

Ans: Option (b) is the answer. The fungus Trichoderma is a biological control being developed for use in the treatment of plant disease. Trichoderma fungi are free-living fungi found in abundance in root habitats.