Biology MCQ, Class-12, Chapter-8, Microbes in Human Welfare

NCERT based Biology MCQ of Class 12th, Chapter-8, Microbes in Human Welfare with brief explanation for competitive exams like TGT HTET, KVS PGT, SSC and all other state competition exams. 

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Science MCQ, Class 10th, Chapter-9, Light: Reflection and Refraction

NCERT Based MCQ with Explanation:

1. Which bacteria are primarily responsible for converting milk into curd?

(a) Streptococcus

(b) Lactobacillus

(c) Propionibacterium

(d) Saccharomyces

Explanation: Lactobacillus, commonly known as lactic acid bacteria (LAB), grows in milk and produces acids that coagulate milk proteins, converting it into curd. This is explicitly stated in the chapter.

2. What gas is responsible for the puffed-up appearance of dough used in making dosa and idli?

(a) Oxygen

(b) Nitrogen

(c) Carbon dioxide

(d) Methane

Explanation: The chapter mentions that the fermentation of dough for dosa and idli by bacteria produces CO₂ gas, causing the dough to puff up.

3. Which microorganism is used to ferment the dough for bread-making?

(a) Lactobacillus

(b) Saccharomyces cerevisiae

(c) Propionibacterium sharmanii

(d) Aspergillus niger

Explanation: Saccharomyces cerevisiae, known as baker’s yeast, is used to ferment the dough for bread, as noted in the text.

NCERT Based MCQ, Science -10th

4. What causes the large holes in Swiss cheese?

(a) Production of methane

(b) Production of carbon dioxide

(c) Presence of fungi

(d) Action of lactic acid

Explanation: The large holes in Swiss cheese are due to the production of a large amount of CO₂ by Propionibacterium sharmanii, as described in the chapter.

5. Which traditional drink from southern India is made by fermenting palm sap?

(a) Wine

(b) Toddy

(c) Beer

(d) Rum

Explanation: The chapter identifies 'Toddy' as a traditional drink made by fermenting sap from palms in southern India.

6. What nutritional benefit does curd gain from fermentation by LAB?

(a) Increased protein content

(b) Increased vitamin B₁₂

(c) Increased sugar content

(d) Increased fat content

Explanation: The text states that curd’s nutritional quality improves due to an increase in vitamin B₁₂ during fermentation by LAB.

7. Which microbe gives Roquefort cheese its specific flavor?

(a) Bacteria

(b) Yeast

(c) Fungi

(d) Virus

Explanation: Roquefort cheese is ripened by growing a specific fungus on it, which imparts its characteristic flavor, as per the chapter.

8. What role do LAB play in the human stomach?

(a) Digest proteins

(b) Check disease-causing microbes

(c) Produce antibiotics

(d) Ferment sugars

Explanation: LAB in the stomach help prevent the growth of disease-causing microbes, as mentioned in the text.

9. Which metabolic pathway likely produces CO₂ in dough fermentation?

(a) Glycolysis

(b) Citric acid cycle

(c) Alcoholic fermentation

(d) Oxidative phosphorylation

Explanation: The production of CO₂ in dough fermentation suggests alcoholic fermentation, a process carried out by yeast or bacteria, as implied in the chapter.

10. What is the source of bacteria for fermenting dosa and idli dough?

(a) Soil

(b) Air

(c) Water

(d) All of the above

Explanation: The chapter asks where the bacteria come from and implies they are naturally present in the environment (soil, air, water), making "all of the above" plausible.

Biology MCQ, Class-11th, Chapter-10, Cell Cycle and Cell Division

11. What type of vessel is used for large-scale industrial microbial production?

(a) Incubator

(b) Fermentor

(c) Bioreactor

(d) Distiller

Explanation: The chapter specifies that industrial-scale production requires growing microbes in fermentors.

12. Which yeast is used to produce ethanol in fermented beverages?

(a) Aspergillus niger

(b) Saccharomyces cerevisiae

(c) Trichoderma polysporum

(d) Monascus purpureus

Explanation: Saccharomyces cerevisiae, also called brewer’s yeast, is used for fermenting cereals and fruit juices to produce ethanol, as per the text.

13. Which beverage is produced without distillation?

(a) Whisky

(b) Beer

(c) Rum

(d) Brandy

Explanation: The chapter states that beer and wine are produced without distillation, unlike whisky, rum, and brandy.

14. Who discovered Penicillin?

(a) Ernest Chain

(b) Howard Florey

(c) Alexander Fleming

(d) Louis Pasteur

Explanation: Alexander Fleming discovered Penicillin by observing a mould inhibiting Staphylococci growth, as detailed in the chapter.

15. From which mould was Penicillin originally derived?

(a) Aspergillus niger

(b) Penicillium notatum

(c) Trichoderma polysporum

(d) Monascus purpureus

Explanation: The chapter states that Penicillin was named after the mould Penicillium notatum by Fleming.

16. Which antibiotic was extensively used during World War II?

(a) Streptomycin

(b) Penicillin

(c) Tetracycline

(d) Chloramphenicol

Explanation: The text notes that Penicillin was widely used to treat wounded American soldiers in World War II.

17. Which microbe produces citric acid industrially?

(a) Lactobacillus

(b) Aspergillus niger

(c) Acetobacter aceti

(d) Clostridium butylicum

Explanation: Aspergillus niger, a fungus, is listed in the chapter as a producer of citric acid.

18. What is the function of Streptokinase produced by Streptococcus?

(a) Antibiotic production

(b) Clot removal

(c) Cholesterol reduction

(d) Immunosuppression

Explanation: Streptokinase is described as a “clot buster” used to remove blood clots in heart attack patients.

19. Which microbe produces the immunosuppressive agent Cyclosporin A?

(a) Trichoderma polysporum

(b) Monascus purpureus

(c) Saccharomyces cerevisiae

(d) Bacillus thuringiensis

Explanation: The chapter identifies Trichoderma polysporum as the source of Cyclosporin A, used in organ transplants.

20. What do Statins, produced by Monascus purpureus, help reduce?

(a) Blood pressure

(b) Blood cholesterol

(c) Blood sugar

(d) Blood clots

Explanation: Statins are commercialized as blood-cholesterol-lowering agents, as stated in the text.

21. What is the main component of municipal wastewater?

(a) Industrial waste

(b) Human excreta

(c) Agricultural runoff

(d) Chemical pollutants

22. What is the purpose of sewage treatment plants (STPs)?

(a) Generate electricity

(b) Produce biogas

(c) Make sewage less polluting

(d) Recycle drinking water

23. Which process removes floating debris in primary sewage treatment?

(a) Sedimentation

(b) Filtration

(c) Aeration

(d) Digestion

24. What forms the primary sludge in sewage treatment?

(a) Floating debris

(b) Settled solids

(c) Effluent

(d) Aerobic bacteria

25. What is the role of aeration tanks in secondary sewage treatment?

(a) Remove large particles

(b) Grow aerobic microbes

(c) Produce biogas

(d) Filter effluent

26. What does BOD measure in sewage water?

(a) Bacterial population

(b) Organic matter content

(c) Oxygen levels

(d) pH value

27. What happens to the effluent after BOD is reduced in secondary treatment?

(a) Released into rivers

(b) Sent to anaerobic digesters

(c) Recycled as drinking water

(d) Used to produce biogas

28. Which gas is NOT produced by anaerobic sludge digestion?

(a) Methane

(b) Hydrogen sulphide

(c) Carbon dioxide

(d) Oxygen

29. What is the role of activated sludge in sewage treatment?

(a) Remove large debris

(b) Serve as inoculum

(c) Produce antibiotics

(d) Clarify water

30. Which initiative aims to reduce river pollution in India?

(a) Ganga Action Plan

(b) Clean India Mission

(c) Green Revolution

(d) Blue Revolution

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