NEET Biology Microbes in Human Welfare Important Questions Set 01

These Class 12 NEET Biology important questions on Microbes in Human Welfare give 45 questions with step-by-step answers, arranged as very short, short and long answer types, as asked in school and board examinations. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. What are microbes?
Answer: Microbes are very small organisms that not visible with naked eye. e.g., virus, viroids, prions.

Question 2. What is Baker's yeast?
Answer: Saccharomyces cerevisiae.

Question 3. Name the curd forming bacterium.
Answer: Lactic Acid Bacteria (LAB).

Question 4. Define fermentor.
Answer: Fermentors are large containers where microbes are provided with nutrient solution to produce desirable products.

Question 5. Who discovered antibiotic?
Answer: Alexander Fleming (1928).

Question 6. Name the microbe that yields lactic acid.
Answer: Lactic acid bacteria (LAB).

Question 7. Why are pectinase and proteases added to fruit juices?
Answer: Pectinases and proteases are used to clarify the fruit juices.

Question 8. Name the clot buster enzyme.
Answer: Streptokinase.

Question 9. What is activated sludge?
Answer: The effluent from primary treatment is passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called activated sludge.

Question 10. What is the major component of biogas?
Answer: Methane.

Short Answer Type Questions

Question 11. Name the various microbes that are devoid of cellular structure. Which one of them is made exclusively of protein, exclusively of nucleic acid and both [nucleic acid and protein].
Answer: Microbes devoid of cellular structure are virus, prions and viroids. Prions are exclusively made of Protein. Viroids are made exclusively of Nucleic acid. Virus is made of both protein and nucleic acid.

Question 12. How is Idli prepared?
Answer: The dough of Idli is fermented by bacteria, the puffed-up appearance of dough is due to production of CO₂.

Question 13. What is the reason of large holes in Swiss cheese? Name the fungus used in ripening of Roquefort cheese.
Answer: Large holes in Swiss cheese is due to production of large amount of CO₂ by bacterium Propionibacterium sharmanii. Fungus used in ripening of roquefort cheese is Penicillium roquefortii.

Question 14. Name four fermented beverages.
Answer: (i) Wine
(ii) Beer
(iii) Rum
(iv) Whisky

Question 15. Name two antibiotics that are able to prevent growth of microbes.
Answer: Penicillin and Tetracycline

Question 16. What are the uses of statins? Give their source.
Answer: Statins are produced by yeast Monascus purpureus and is used as blood cholesterol lowering agent.

Question 17. What is the use of cyclosporin A? Give its source.
Answer: Cyclosporin A is used as an Immunosuppressive agent in organ transplant patients. It is produced by fungus Trichoderma polysporum.

Question 18. Explain the scientific reason for growing a leguminous crop like groundnut prior to a cereal crop.
Answer: The root nodules of leguminous plants contain Rhizobium (Symbiotic association) that fixes the atmospheric nitrogen into ammonia in soil. Which is used by cereal crop as nutrient.

Question 19. What is biogas? Give its composition and use.
Answer: Biogas is mixture of gases produced by microbial activity. Composition of biogas - Methane, CO₂, H₂, H₂S etc. It is used for cooking and lighting.

Question 20. Name two cyanobacteria. Explain how they serve as main source of biofertilizers.
Answer: Anabaena and Nostoc. Cyanobacteria fixes atmospheric nitrogen in the soil and replenish soil nutrients.

Question 21. What are biofertilizers? Why are they preferred over chemical fertilizers?
Answer: Biofertilizers are organisms that enrich the nutrient quality of the soil. They are preferred over chemical fertilizers because biofertilizers are non-polluting and replenish soil-nutrients.

Question 22. How has the fungus, Trichoderma polysporum, proved to be very essential to organ transplant patients.
Answer: Fungus, Trichoderma polysporum produces Cyclosporin A, a bioactive molecule, that is used as an immunosuppressive agent in organ-transplant patients.

Question 23. Baculoviruses are excellent candidates for Integrated Pest Management in an ecologically sensitive area. Explain giving two reasons.
Answer: Baculoviruses are pathogens that attack insects and other arthropods. They are excellent candidates for integrated pest management in an ecologically sensitive area because they are
(i) Species-specific
(ii) Have no negative impact on plants, birds, mammals, fish or on non-target insects.

Question 24. What is organic farming? Why is it suggested to switch over to organic farming?
Answer: Organic farming is raising of crops through the use of biofertilizers that provide optimum nutrients to crop plants. There are many problems like environmental pollution associated with over use of chemical fertilizer, so need to switch to organic farming.

Question 25. How does biofertilizers enrich the fertility of soil?
Answer: Biofertilizers like bacteria and Cyanobacteria fix atmospheric nitrogen into ammonia which is used by plant as nutrient. Fungi symbiotically absorb phosphorus from soil and passes it to the plant. Thus enriching the fertility of soil.

Question 26. What are flocs? Explain their role.
Answer: FLOCS - flocs are the masses of bacteria associated with fungal filaments to form mesh like structures. Role - While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces BOD (Bio-chemical oxygen demand).

Question 27. What are antibiotics? How first antibiotic penicillin was discovered?
Answer: Antibiotics are chemical substances, which are produced by some microbes and kill or retard growth of other (disease causing) microbes. The first antibiotic Penicillin was discovered by Alexander Fleming, while working on Staphylococci bacteria, he observed a mould growing in one of his unwashed culture plates, around which Staphylococci could not grow. He found that the chemical was produced by fungi and named it Penicillin after the mould Penicillium notatum.

Question 28. How do Ladybird beetles and Dragonflies act as biocontrol agents?
Answer: Ladybird, a beetle with red and black markings is useful in controlling aphids. Dragonflies, are useful to get rid of the mosquitoes.

Question 29. How do plants benefit from having mycorrhizal symbiotic association?
Answer: Plants having mycorrhizal symbiotic association show-resistance to root-borne pathogens, tolerance to salinity and drought, and overall increase in plant growth and development.

Question 30. How does addition of small amount of curd to fresh milk help in formation of curd? Mention a nutritional quality that gets added to the curd.
Answer: A small amount of curd added to fresh milk as inoculum or starter contains millions of LAB, which at suitable temperature multiply and digest milk proteins converting milk into curd. Vitamin B₁₂ is nutritional quality that gets added to the curd.

Long Answer Type Questions

Question 31. Describe the use of microbes in household products.
Answer: Microbes in household products :
(i) Curd - Micro-organisms such as Lactobacillus and others commonly called Lactic acid bacteria (LAB) grow in milk and convert it into curd.
(1) During growth, the LAB produce acids that coagulate and partially digest the milk proteins.
(2) The starter or inoculum contains millions of LAB, which at suitable temperature multiply, thus converting milk to curd.
(3) Curd is more nutritious than milk as it contains a number of vitamins especially vit B₁₂.
(ii) Cheese - One of the oldest food items in which microbes were used is cheese. It is degraded concentrate of milk fat and casein.
(1) Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity determined by the microbes used.
(2) For example - Large holed Swiss cheese is ripened with the help of bacterium called Propionibacterium sharmanii. Roquefort cheese is ripened by fungus Penicillium roquefortii.
(iii) Bread - Bread is prepared from dough, which is fermented using Baker's yeast - Saccharomyces cerevisiae. Puffed - up appearance of dough is due to production of CO₂ during fermentation. CO₂ gas along with ethyl alcohol evaporates during baking, making bread porous and soft.
(iv) Dosa and Idli - The fermented preparation of rice and black gram, prepared by using bacteria.
(v) Toddy - A traditional drink in some parts of south India is made by fermenting sap from palm - Caryota urens. It contains 6% alcohol.
(vi) Other food microbes are used to ferment is soyabean and bamboo shoots to make foods.

Question 32. Why organic farmers do not recommend the eradication of insect pests? Explain giving reasons.
Answer: (i) The organic farmer believes that biodiversity furthers health. The more variety a landscape has, the more sustainable it is.
(ii) Organic farmer holds the view that the eradication of the creatures that are often described as pests is possible but is undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive.

Question 33. Describe important enzymes obtained through microbial activity.
Answer: A number of enzymes are produced commercially for industrial and medical uses.
(i) Lipases - These are used in detergent formulation and are helpful in removing oily stains from laundry.
(ii) Pectinases and Proteases - They help in clarifying fruit juices making them clearer as compared to those made at home.
(iii) Streptokinase - It is produced by the bacterium Streptococcus and is modified by genetic engineering. It is used as 'Clot buster' for removing clots from the blood vessels of patients who have undergone myocardial infraction leading to heart attack.

Question 34. Describe Cyclosporin A, statins and important organic acids manufactured with the help of microbes.
Answer: (1) Cyclosporin A - It is used as an immunosuppressive agent in organ transplant patients, is produced by the fungus Trichoderma polysporum.
(2) Statins - These are produced by the yeast Monascus purpureus. Statins have been commercialised as blood-cholesterol lowering agents. It acts, competitively inhibiting the enzyme responsible for the synthesis of cholesterol.
(3) Certain microbes have ability to convert carbohydrates into organic acid. Organic acids produced through microbial activity are:
(a) Acetic acid - Produced by Acetobacter aceti
(b) Citric acid - Produced through fermentation activity of Aspergillus niger from the carbohydrate rich solution.
(c) Lactic acid - It is obtained from carbohydrate solutions with the help of Lactic acid bacteria. Lactic acid is also present in whey of cheese.
(d) Butyric acid - It is formed through fermentation carried out by Clostridium butylicum.

Question 35. How are microbes involved in production of biogas?
Answer: Biogas is a mixture of gases (containing predominantly methane) produced by microbial activity and which may be used as fuel. Microbes produce different types of gaseous end-products during growth and metabolism. Certain bacteria, which grow anaerobically on cellulosic material, produce large amount of Methane along with CO₂ and H₂. These bacteria are collectively called as methanogens and one such common bacterium is Methanobacterium.

Question 36. Describe biofertilisers.

Answer:

Biofertilisers are organisms that enrich the nutrient quality of soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria

(i) BACTERIA - Rhizobium forms symbiotic association with root nodules of leguminous plants. These bacteria fix atmospheric nitrogen into ammonia, which is used by plants as nutrients.

Bacteria like Azospirillum and Azotobacter can fix atmospheric nitrogen while free living in the soil, thus enriching the nitrogen content of soil.

(ii) FUNGI - Fungi also forms symbiotic association with roots of higher plants, known as Mycorrhiza. Many members of the genus Glomus form Mycorrhiza. The fungal symbiont absorbs phosphorus from soil and passes it to plants. Plants having such associations also show resistance to root borne pathogens, tolerance to salinity and drought, and overall increase in plant growth and development. In return fungi get shelter and food from this association.

(iii) CYANOBACTERIA - Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g., Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae (BGA) also adds organic matter to the soil and increases its fertility.

(iv) Currently a number of biofertilisers are available commercially in the market and farmers use these regularly in their fields to replenish soil nutrients and to reduce dependence on chemical fertilisers.

Question 37. Give an account of role of microbes in preparation of alcoholic beverages.

Answer:

(i) In industry, microbes are used to synthesise a number of products valuable to human beings like beverages. Production on an industrial scale, requires growing microbes in very large vessels called Fermentors.

Fermentors
(ii) Yeast species used in alcoholic fermentation are Saccharomyces cerevisiae, commonly called Brewer's yeast.

(iii) Malted cereals and fruit juices produce ethanol by fermentation.

(iv) Depending on the type of raw material used for fermentation and the type of processing [with or without distillation] different types of alcoholic drinks are obtained.

Wine and beer are produced without distillation [Low alcohol concentration] while whisky, brandy and rum are produced by distillation of fermented broth [High alcohol concentration].

Question 38. Draw well labelled diagram of biogas plant and describe it.

Answer:

A well-labelled diagram should show these parts: The Biogas plant consists of; Gas; Gas-holder; Digester; A typical biogas plant.

(i) A concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed.
(ii) A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to microbial activity. It has an outlet which is connected to a pipe to supply biogas to nearby houses.

Dung Water (CH₄ + CO₂ + ------) Sludge

(iii) The spent slurry is removed through another outlet and may be used as fertiliser. Cattle dung is available in large quantities in rural areas where cattles are used for a variety of purposes. So biogas plants are more often build in rural areas. The biogas thus produced is used for cooking and lighting.

Question 39. Explain the physical process of sewage treatment.
Answer: It is a primary treatment which involves removal of large and small particles from sewage through filtration and sedimentation.
(i) Sequential filtration - Floating debris is removed by sequential filtration.
(ii) Sedimentation - The grit [soil and small pebbles] are removed by sedimentation. All solids that settle form the primary sludge, and the supernatant forms the primary effluent. The effluent from the primary settling tank is taken for biological or secondary treatment.

Question 40. Explain the biological process of sewage treatment.
Answer: (i) Primary effluent is passed into large aeration tanks, where it is constantly agitated mechanically and air is pumped into it.
(ii) Aeration tanks show vigorous growth of useful aerobic heterotrophic microbes into flocs. Flocs are masses of bacteria associated with fungal filaments to form mesh like structures.
(iii) While growing, these microbes consume the major part of the organic matter present in the effluent. This significantly reduces the BOD (Biochemical oxygen demand) of the effluent.
(iv) The sewage is treated till the BOD is reduced. Once the BOD of sewage or waste water is reduced significantly, the effluent is then passed into a settling tank where bacterial flocs are allowed to sediment. This sediment is called activated sludge.
(v) A small part of the activated sludge is pumped back into the aeration tank to serve as inoculum. The remaining major part of sludge is pumped into large tanks called anaerobic sludge digester.

Question 41. (a) What do you understand by biocontrol?
(b) Why biocontrol is preferred over conventional farming?
Answer: (a) Biocontrol - It refers to the use of biological methods for controlling plants diseases and pests.
(b) The chemicals like insecticides and pesticides are toxic and extremely harmful to human beings and animals alike, and have been polluting our environment (soil, ground water), fruits, vegetables and crop plants. Our soil is also polluted through use of weedicides to remove weeds. These conventional farming practices which often use chemical methods to kill both useful and harmful life forms indiscriminately, this is holistic approach that seeks to develop an understanding of the webs of interaction between the group of organisms that constitute the field fauna and flora.

Question 42. (a) Draw well labelled diagram of a Bacteriophage.
(b) Give examples of biocontrol agents.

Answer:

(a)

Head

Collar Tail Plate

Pins Prongs

Bacteriophage
(b) (i) Ladybird beetle controls aphids.
(ii) Dragonflies control mosquitoes.
(iii) Bacillus thuringiensis (Bt) controls butterfly caterpillars.
(iv) Fungus Trichoderma is effective against plant pathogens.
(v) Baculoviruses are pathogens that attack insects and other arthropods. These are species-specific, having narrow spectrum insecticidal applications.

Question 43. Fill in the blanks.
(a) ______ is the traditional drink of some parts of Southern India, made by fermenting sap from palms.
(b) Cyclosporin A is used as ________.
(c) Masses of bacteria associated with fungal filament to form mesh like structures are called _______.
(d) _______ bacteria are commonly found in the anaerobic sludge during sewage treatment.
(e) _______ are autotrophic microbes which can fix atmospheric nitrogen.
Answer: (a) Toddy
(b) Immunosuppressive agent in organ transplant
(c) Flocs
(d) Methanogenic
(e) Cyanobacteria

Question 44. Mark true or false in the following statements :
(a) Bacteria and Fungi are used to impart texture, taste and flavour to cheese.
(b) The first antibiotic was discovered in the culture plates of Streptococcus.
(c) Statins are competitive inhibitor of enzyme responsible for cholesterol synthesis.
(d) Greater the BOD of waste water, less is its polluting potential.
(e) Under river action plans, it is proposed to built a large number of sewage treatment plants.
Answer: (a) True
(b) False
(c) True
(d) False
(e) True

Question 45.

Identify the following.

Answer:

(a) Tobacco mosaic virus (TMV)
(b) Rod-shaped bacteria
(c) Colonies of bacteria
(d) Fungal colony
(e) Spherical bacteria
(f) Adenovirus