Exams › NEET › Biology › Microbes in Human Welfare
84 questions with worked solutions.
Q1. Which of the following is put into Anaerobic sludge digester for further sewage treatment?
Answer: Activated sludge
Activated sludge is the microbial biomass collected after secondary treatment and is commonly sent to an anaerobic sludge digester for stabilization. Floating debris and primary sludge are removed earlier, while effluents of primary treatment are not the sludge fed to the digester.
Answer: (b) (ii) (iv) (iii) (v)
Lactobacillus converts milk into curd, Saccharomyces cerevisiae is baker’s yeast used in bread making, Aspergillus niger is used to produce citric acid, and Acetobacter aceti produces acetic acid (vinegar). These pairings give (b) → (ii), (iv), (iii), (v).
Q3. Which of the following in sewage treatment removes suspended solids?
Answer: Primary treatment
Primary treatment is the initial physical stage of sewage treatment, where screening and sedimentation remove suspended solids. Secondary treatment mainly breaks down dissolved organic matter biologically, while tertiary treatment is for advanced polishing.
Q4. Which of the following is a commercial blood cholesterol lowering agent?
Answer: Statin
Statins are the standard commercial drugs used to lower blood cholesterol by inhibiting HMG-CoA reductase, a key enzyme in cholesterol synthesis. The other options have different roles: cyclosporin A is an immunosuppressant, streptokinase dissolves clots, and lipases digest fats.
Q5. What gases are produced in anaerobic sludge digesters?
Answer: Methane, Hydrogen Sulphide and CO2
In anaerobic sludge digesters, microorganisms break down organic matter without oxygen, producing biogas. This biogas commonly contains methane, carbon dioxide, and hydrogen sulphide, which matches the correct option.
Q6. The guts of cow and buffalo possess:
Answer: Methanogens
Cow and buffalo are ruminants with anaerobic gut compartments where methane-producing archaea thrive. These organisms are methanogens, which help digest cellulose-rich food by fermenting in the absence of oxygen.
Q7. Which of the following is correctly matched for the product produced by them?
Answer: Saccharomyces cerevisiae : Ethanol
Saccharomyces cerevisiae is yeast used in alcoholic fermentation, where it converts sugars into ethanol and carbon dioxide. The other pairs are mismatched because those organisms are associated with different products.
Q8. During sewage treatment, biogases are produced which include:
Answer: methane, hydrogen sulphide, carbon dioxide
Sewage sludge breaks down anaerobically, producing biogas mainly composed of methane and carbon dioxide, with hydrogen sulphide as a common impurity. Oxygen and nitrogen are not typical major products of this process.
Q9. Curing of tea leaves is brought about by the activity of
Answer: bacteria
Curing of tea leaves involves microbial action that helps bring about the desired chemical changes during processing. Among the options, bacteria are the organisms associated with this curing process.
Q10. Monascus purpureus is a yeast used commercially in the production of:
Answer: blood cholesterol lowering statins
Monascus purpureus produces monacolins, especially lovastatin-like compounds, which are used as blood cholesterol-lowering statins. It is not mainly used for ethanol, streptokinase, or citric acid production.
Q11. Yeast is used in the production of:
Answer: Bread and beer
Yeast ferments sugars, producing carbon dioxide and alcohol. Carbon dioxide makes dough rise in bread, and alcohol fermentation is essential in beer production.
Q12. A good producer of citric acid is:
Answer: Aspergillus
Aspergillus, especially Aspergillus niger, is widely used industrially to produce citric acid because it secretes large amounts during fermentation. The other options are better known for different products or metabolic roles.
Answer: Trichoderma sp. against certain plant pathogens
Trichoderma species are beneficial fungi used as biocontrol agents against several plant pathogens, so this is an example of microbial biological control. The other options involve a virus against the wrong target, a genetically modified crop, or an insect predator.
Q14. Which bacteria is utilized in gobar gas plant?
Answer: Methanogens
Gobar gas plants work by anaerobic decomposition of organic waste, and methane is produced by methanogenic microorganisms. These methanogens are the key bacteria used in biogas formation.
Q15. A good green manure in rice fields is:
Answer: (b) Azolla
Azolla is a floating aquatic fern that forms a symbiotic association with nitrogen-fixing Anabaena, so it adds nitrogen to paddy fields. That makes it a well-known green manure for rice cultivation.
Q16. Which fish can be used in biological control of mosquitoes/Larvicidal fish is
Answer: Gambusia
Gambusia, especially Gambusia affinis, is widely used in biological control because it feeds on mosquito larvae in water bodies. The other options are not standard larvicidal fish for mosquito control.
Answer: Lignin
Lignin is a complex aromatic polymer that most anaerobic microorganisms cannot efficiently degrade. In biogas production, carbohydrates, proteins, and fats are digested much more readily, while lignin largely remains undegraded.
Q18. Which steroid is used for microbial transformation?
Answer: Progesterone
Progesterone is a standard substrate for microbial transformation because many microorganisms can selectively oxidize, reduce, or hydroxylate it. It is widely used in biotransformation research to produce useful steroid intermediates.
Q19. Pasteurization of milk involve heating for
Answer: 30 minutes at about 65°C
Pasteurization uses controlled heating to destroy harmful microbes while preserving milk quality. The classic method is heating milk to about 63–65°C for around 30 minutes, which matches option C.
Q20. Which of the following plant species you would select for the production of bioethanol?
Answer: Zea mays
Zea mays (maize/corn) is a starch-rich crop widely used as a feedstock for bioethanol production because its carbohydrates can be converted into sugars and fermented. The other options are mainly oilseed plants better suited for biodiesel.