CBSE Class 12 Biology HOTs Microbes In Human Welfare

Question. Given below is the diagram of a bacteriophage. In which one of the option, all the six parts A, B, C, D, E and F are correct? (Image 4)
(a) A–Head, B–Tail, C–Collar, D–Pins, E–Plate, F–Prongs
(b) A–Head, B–Collar, C–Tail, D–Plate, E–Pins, F–Prongs
(c) A–Head, B–Tail, C–Collar, D–Plate, E–Prongs, F–Pins
(d) A–Head, B–Collar, C–Tail, D–Pins, E–Plate, F–Prongs
5 Which of the following bacteria convert milk into curd?
(a) Propionibacterium shermanii
(b) Saccharomyces cerevisiae
(c) Lactobacillus
(d) Thermophilic bacteria
Answer : B

Question. Microorganisms such as Lactobacillus are commonly called
(a) Citric Acid Bacteria (CAB)
(b) Lactic Acid Bacteria (LAB)
(c) Tartaric Acid Bacteria (TAB)
(d) Formic Acid Bacteria (FAB)
Answer : C

Question. Which of the following food items are produced through fermentation by the microorganisms?
I. Idli II. Dosa
III. Toddy IV. Cheese
Choose the correct option.
(a) I, II and III
(b) I, III and IV
(c) II, III and IV
(d) All of these
Answer : B

Question. Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes?
(a) Sludge digester
(b) Industrial oven
(c) Bioreactor
(d) BOD incubator
Answer : C

Question. The most abundant prokaryotes helpful to human in making curd from milk and in the production of antibiotics are the ones categorised as
(a) cyanobacteria 
(b) archaebacteria
(c) chemosynthetic autotrophs
(d) heterotrophic bacteria
Answer : B

Question. The starter or inoculum is added to the fresh milk in order to convert milk into curd and improves its nutritional quality by increasing
(a) vitamin-B12
(b) protein
(c) calcium
(d) All of these
Answer : A

Question. Study the following flowchart that shows curd formation from milk and select the correct option for A and B. (Image 9)
(a) A–citric acid, B–vitamin-B12
(b) A–lactic acid, B–vitamin-B12
(c) A–lactic acid, B–vitamin-C
(d) A–citric acid, B–vitamin-B2
Answer : B

Question. Which gas is released during the process of fermentation that gives the puffy appearance to dough for making bread?
(a) CO2
(b) CO
(c) O2
(d) H2
Answer : A

Question. Toddy, a traditional drink of Southern India is made by ...A... of sap from …B… tree. Here, A and B refer to
(a) A–fermentation, B–palm
(b) A–fermentation, B–bamboo
(c) A–distillation, B–palm
(d) A–distillation, B–bamboo
Answer : A

Question. Swiss cheese is formed by the bacterium
(a) Aspergillus niger
(b) Lactobacillus
(c) Propionibacterium shemanii
(d) Penicillium roqueforti
Answer : C

Question. Roquefort cheese is formed by ripening with ...A...for a particular flavour. Here A refers to
(a) yeast
(b) fungi
(c) bacteria
(d) None of these
Answer : B 

Question. The alcoholic beverages produced by the distillation of the fermented broth are
(a) wine and beer
(b) wine, whisky and brandy
(c) whisky, brandy and rum
(d) whisky, beer and brandy
Answer : C

Question. Which of the following organisms is used in the production of beverages like wine, beer, whisky brandy or rum?
(a) Clostridium butylicum
(b) Aspergillus niger
(c) Saccharomyces cerevisiae
(d) Penicillium notatum
Answer : C

Question. Microorganisms or microbes are found in
(a) soil, air, water and inside the bodies of living organisms
(b) thermal vents deep in soil
(c) under snow and in highly acidic environments
(d) All of the above
Answer : C

Question. The microscopic proteinaceous infectious agents are
(a) viroids
(b) prions
(c) protozoans
(d) bacteria
Answer : B

Question. Identify the blank spaces A, B, C and D given in the following table and select the correct answer.  (Image 29)
(a) A–Trichoderma polysporum, B–As an immunosuppressive agent in organ transplant patients, C–Yeast, D–As blood-cholesterol lowering agent
(b) A–Trichoderma polysporum, B–As blood-cholesterol lowering agent, C–Protozoa, D–As an immunosuppressive agent in organ transplant patients
(c) A–Clostridium butylicum, B–Used as a clot-buster, C–Yeast, D–As blood- cholesterol lowering agent
(d) A–Clostridium butylicum, B–As blood-cholesterol lowering agent, C–Yeast, D–Used as a clot-buster
Answer : A

Question. Monascus purpureus is a yeast used commercially in the production of 
(a) ethanol
(b) streptokinase for removing clots from the blood vessels
(c) citric acid
(d) blood cholesterol lowering agent, statins
Answer : D

Question. The nutritive medium for growing bacteria and many fungi in the laboratory is called
(a) culture media
(b) fermentation media
(c) baking media
(d) None of the above 
Answer : A

Question. Yeast is used in the production of
(a) citric acid and lactic acid
(b) lipase and pectinase
(c) bread and beer
(d) cheese and butter
Answer : C

Question. Choose the incorrect pair.
(a) Lipases – Used in detergents for removing oil stains
(b) Pectinases and proteases – Used in clarifying bottled juices
(c) Statins – Competitively inhibit the enzyme responsible for cholesterol synthesis
(d) None of the above
Answer : D

Question. Which of the following is used as ‘clot buster’ for removing clots from blood vessels of patient who have undergone myocardial infarction?
(a) Ethanol
(b) Statins
(c) Cyclosporin-A
(d) Streptokinase
Answer : D

Question. Brewer’s yeast is
(a) Penicillium notatum
(b) Trichoderma polysporum
(c) Propionibacterium shermanii
(d) Saccharomyces cerevisiae
Answer : D

Question. Who observed a mould growing in unwashed culture plate while working on Staphylococcus bacterium?
(a) Ernst Chain
(b) Alexander Fleming
(c) Lamarck
(d) Florey
Answer : B 

Question. Antibiotics are used to treat diseases like
(a) diphtheria, whooping cough
(b) plague
(c) leprosy
(d) All of the above
Answer : D

Question. Identify the blank spaces A, B, C and D given in the following table and select the correct answer. (Image 24)
(a) A–Lactobacillus, B–Aspergillus niger, C–Bacterium, D–Penicillin
(b) A–Staphylococcus, B–Clostridium, C–Yeast, D–Penicillin
(c) A–Lactobacillus, B–Microsporum, C–Yeast, D–Penicillin
(d) A–Staphylococcus, B–Microsporum, C–Agaricus, D–Penicillin
Answer : A

Question. Who got Nobel Prize in 1945 for the discovery of penicillin as an antibiotic?
(a) Alexander Fleming
(b) Ernst Chain
(c) Howard Florey
(d) All of these
Answer : D

Question. Which one of the following in sewage treatment removes suspended solids? 
(a) Tertiary treatment
(b) Secondary treatment
(c) Primary treatment
(d) Sludge treatment
Answer : C

Question. Which one of these microbes is used in the commercial production of butyric acid?
(a) Clostridium butylicum
(b) Streptococcus butylicum
(c) Trichoderma polysporum
(d) Saccharomyces cerevisiae
Answer : A

Question. Which of the following is correctly matched for the product produced by them? 
(a) Acetobacter aceti – Antibiotics
(b) Methanobacterium – Lactic acid
(c) Penicillium notatum – Acetic acid
(d) Saccharomyces cerevisiae – Ethanol
Answer : D

Question. Which of the following is a commercial blood cholesterol lowering agent? 
(a) Statin
(b) Streptokinase
(c) Lipases
(d) Cyclosporin-A
Answer : A

Question. Yeast is used in the production of
(a) bread and beer
(b) cheese and butter
(c) citric acid and lactic acid
(d) lipase and pectinase.
Answer : A

Question. A person admitted to hospital as he had myocardial infarction. A cardiologist injected him ‘streptokinase’, why?
(a) It stimulates heart beat.
(b) It reduces hypertension.
(c) It acts as clot buster.
(d) It reduces the level of blood cholesterol.
Answer : C

Question. Ernst Chain and Howard Florey’s contribution was
(a) establishing the potential of penicillin as an effective antibiotic
(b) discovery of streptokinase
(c) production of genetically engineered insulin
(d) discovery of DNA sequence.
Answer : A

Question. Which one of the following is a bacterial biofertiliser?
(a) Anabaena
(b) Nostoc
(c) Rhizobium
(d) Oscillatoria
Answer : C

Question. Select the correct statement from the following.
(a) Biogas is produced by the activity of aerobic bacteria on animal waste.
(b) Methanobacterium is an aerobic bacterium found in rumen of cattle.
(c) Biogas, commonly called gobar gas, is pure methane.
(d) Activated sludge-sediment in settlement tanks of sewage treatment plant is a rich source of aerobic bacteria.
Answer : D

Question. An organism used as a biofertiliser for raising soyabean crop is
(a) Azotobacter
(b) Azospirillum
(c) Rhizobium
(d) Nostoc.
Answer : C

Question. A nitrogen-fixing microbe associated with Azolla in rice fields is
(a) Spirulina
(b) Anabaena
(c) Frankia
(d) Tolypothrix.
Answer : B

Question. Match column I with column II and select the correct option using the codes given below.
Column-I Column-II
A. Citric acid          (i) Trichoderma
B. Cyclosporin A    (ii) Clostridium
C. Statins             (iii) Aspergillus
D. Butyric acid      (iv) Monascus
(a) A-(iii), B-(i), C-(ii), D-(iv)
(b) A-(iii), B-(i), C-(iv), D-(ii)
(c) A-(i), B-(iv), C-(ii), D-(iii)
(d) A-(iii), B-(iv), C-(i), D-(ii)
Answer : B

Question. Select the incorrect match.
(a) Citric acid – Aspergillus niger
(b) Streptokinase – Streptococcus
(c) Butyric acid – Clostridium acetobutylicum
(d) Cyclosporin-A – Monascus purpureus
Answer : D

Question. Match the following organisms with the products they produce.
(A) Lactobacillus         (i) Cheese
(B) Saccharomyces     (ii) Curd cerevisiae
(C) Aspergillus niger   (iii) Citric acid
(D) Acetobacter aceti  (iv) Bread
(v) Acetic acid
Select the correct option.
(A) (B) (C) (D)
(a) (ii) (i) (iii) (v)
(b) (ii) (iv) (v) (iii)
(c) (ii) (iv) (iii) (v)
(d) (iii) (iv) (v) (i)
Answer : C

Question. Which of the following microbes is used for the commercial production of ethanol?
(a) Clostridium butylicum
(b) Trichoderma polysporum
(c) Monascus purpureus
(d) Saccharomyces cerevisiae
Answer : B

Question. Conversion of milk to curd improves its nutritional value by increasing the amount of
(a) vitamin D
(b) vitamin A
(c) vitamin B12
(d) vitamin E.
Answer : C

Question. The primary treatment of sewage water involves
(a) anaerobic bacterial activity
(b) sludge digestion
(c) filtration and sedimentation
(d) aerobic bacterial activity.
Answer : C

Question. Identify the organism shown in the given diagram.
(a) Bacteria
(b) Bacteriophage
(c) TMV
(d) HIV
Answer : C

Question. Viruses of the genus Nucleopolyhedrovirus are employed as
(a) gobar gas producers
(b) biological control agents
(c) anaerobic sludge digesters
(d) atmospheric nitrogen fixing agents.
Answer : B

Question. Select the correct pair of microorganism and the product obtained from it.
(a) Monascus purpureus - produces large holes in Swiss cheese.
(b) Saccharomyces cerevisiae - used for making wine and beer after distillation.
(c) Streptococcus - produces streptokinase which is used to remove clots.
(d) Aspergillus niger - produces citric acid and butyric acid.
Answer : C

Question. Microbe used for biocontrol of pest butterfly caterpillars is
(a) Saccharomyces cerevisiae
(b) Bacillus thuringiensis
(c) Streptococcus sp.
(d) Trichoderma sp.
Answer : B

Question. Select the mismatch.
(a) Rhodospirillum – Mycorrhiza
(b) Anabaena – Nitrogen fixer
(c) Rhizobium – Alfalfa
(d) Frankia – Alnus
Answer : A

Question. Refer to the given figure and select the correct match.

(a) A-Fungal colony, B-Bacterial colony
(b) A-Viral colony, B-Bacterial colony
(c) A-Bacterial colony, B-Viral colony
(d) A-Bacterial colony, B-Fungal colony
Answer : D

Chapter 10. MICROBES IN HUMAN WELFARE

Question. Drinks like Whisky and Rum are more intoxicating than wine. Why? 
Answer. produced without distillation and whisky and rum are produced by distillation of the fermented broth.

Question. Can we imagine a world without antibiotics? Explain briefly. 
Answer. No, because, Antibiotics are needed to kill millions of microbes which cause many deadly diseases like plague, whooping cough, dysphasia etc.

Question. Bottled juices are clearer compared to homemade juice. Give reason.
Answer. Bottled juices are clarified by the use of pectinases and proteases.

Question. Which one of these is a proteinaceous infecting agent? 
Answer. Prions are proteinaceous infecting agents.
a) Viroids, b) prions, c) protern, d) wat.

Question. An organic farmer requires a bio control agent which is species specific and has no negative impact on non-target organism. Suggest the name of such a bio control agent.
Answer. Nucleopolyhedrovirus

Question. Scientists have succeeded in introducing toxin gene of Bacillus thuringiensis into plants like cotton. What purpose is achieved through this action? 
Answer. Pest resistant cotton plant.

Question. A small amount of curd was added to cold milk for converting it into curd. But milk did not get curdled. Why? 
Answer. Optimum temperature is needed for the action of lacto bacillus and to convert milk to curd. Bacteria becomes inactive at low temperature

Question. Consuming curd keeps the gastro-intestinal tract in tact. Give reason. 
Answer. Curd contains lactic acid bacteria which checks the growth of disease causing microbes and protects the gastro intestinal tract

Question. On fermentation the dough of idli and dosa puffs up. Which metabolic pathway is responsible for this process? 
Answer. Cellular respiration/anaerobic respiration in bacteria produces CO2 gas which puffs up the dough

Question. How do lactic acid bacteria help in increasing the nutritional quality of curd?
Answer. The nutritional quality of curd is improved by Lactic acid bacteria by increasing vitamin B12

Question. The excreta of cattle do not contain any cellulose but human excreta may contain cellulose. Why? 
Answer. The rumen of cattle contains methanogens which help in the digestion of cellulose but these bacteria are not present in human stomach

Question. Antibiotics are always sold in combination with lactobacillus. Why? 
Answer. Antibiotics may kill even the useful bacteria present in the digestive tract LAB will protect some microbes in the digestive tract and enhance the production of vitamin B12.

Question. Why are some microbes useful in detergent formulation? 
Answer. Some microbes produce enzymes like lipases which help in removing oil stain when used in detergent formulation.

Question. Microbes release gases during metabolism. How will it help in the production of energy? 
Answer. Some microbes mainly methanogens release large quantities of methane along with CO2 and H2S during metabolism and these gases are used for the production of biogas which is a good source of energy

Question. Why does 'Swiss-cheese' contain large holes?. 
Answer. The large holes on 'Swiss cheese' are due to production of large amount of CO2 during fermentation by the bacteria Propionibacterium sharmani.

Question. In what way the relationship between BOD and organic matter in Sewage will be useful in ecology?
Answer. To determine pollution it helps. More organic waste BOD increases. 

Question. Why do bottled fruit juices appear clearer than the home made ones?
Answer. Bottle fruit juices are treated with the yeast Saccharomyces cervisiae. 

Question. What is the principle behind the conversion of milk into curd and partial digestion of milk protein performed by Lactic Acid Bacteria?
Answer. i) Coagulation
ii) Lactic acid produced by LAB coagulate and partially digest the milk protein.

Question. Wine and beer are different from whisky and brandy though they are all alcoholic beverages. What is the name of the process that brings out this difference?
Answer. Wine & Beer is produced without distillation. Whisky & brandy are produced by distilliation.

Question. Name the group of bacteria that are capable of living at high temperature above 1000C. How does it become possible by these bacteria?
Answer. Thermoacidophils. This bacterial Enzyme is resistant to high tem.

Question. Why do doctors prescribe Streptokinases for brain hemorrhage patients? Mention the source of industrial production of this biomolecule.
Answer. streptokinase is a‘clot buster’ for removing the blood clots from blood vessels.Bio molecules are produced from Steptococcus Bacteria.

2 marks

Question. A farmer was suggested to apply certain microbial culture in his field to increase the yield. Suggest the types of microbes he could use in his paddy field and how do they help in increasing the yield. 
Answer. The microbial culture containing anabaena, Oscillatoria or Nostoc. They act as biofertilizer by fixing the atmospheric nitrogen in the soil and thereby increasing the soil fertility

Question. It was observed that certain plant roots are infected by fungus. in spite of this infection the plant showed increased growth and development. Give reason.
Answer. The plant roots which are infected by fungi form symbiotic association with them and the fungi help the plant to absorb phosphorus from the soil and the plant becomes resistant to salinity and drought thus this symbiotic association called mycorrhiza help in the development of the plant.

Question. Arrange the steps in sewage treatment in proper sequence. 
a) Anaerobic sludge digestion
b) 'Floc' formation
c) Primary effluent in aeration tank
d) Formation of biogas
e) Constant agitation in presence of oxygen.
f)Digestion by anaerobic bacteria
Answer. The proper sequence is c-e-b-a-f-d

Question. Bacteria that convert effluent into activated sludge play one more beneficial side.Mention the role.
Answer. A small portion of the activated sludge containing bacteria is pumped back into the aeration tank to act as inoculums.

 

Question. In the given figure label X & Y and explain the functioning of the below plant.
Answer. x-gas holder, y-Digester.

Question. How does Monascus help in lowering blood-cholesterol? 

Answer. Statin produced by Monascus purpureus competitively inhibit the enzyme responsible for synthesizing cholesterol

 

Question. Complete the given table

 

Answer. i) Citric acid 

ii) saccharomyces cerevisiae 

iii) Trichoderma Polysporum 

iv) Acetobacter aceti 

v) Statin 

vi)Streptokinas

 

 

3 marks

Question. Drinks like Whisky and Rum are more intoxicating than wine. Why? 
Answer. produced without distillation and whisky and rum are produced by distillation of the fermented broth.

Question. For what significant properties the Baculoviruses are considered as best Biological control agent?. Mention its importance in organic farming. 

Answer. I) Baculo viruses attack the specific insects & arthropods. They have no negative impact on plants, birds, mammals or even other non-target insects. The desirable aspect is conservation of beneficial insects. Organic farming uses biopesticides & biofertilizers. Baculo viruses are used as good biopesricides.

 

Question. Give one example and one use of the following:- 

     i) Free living fungi 

     ii) Symbiotic fungi 

     iii) Free living bacteria

 

Answer. I) Free living fugi – Trichoderma – used as biocontrol agent. 

ii) Symbolic fungi – Glomus – helps in absorbtion of nutrients from soil. 

iii) Freeliving bacteria – Azotobactor – helps in increasing yield by fixing atmospheric N2 & making it available to the plants.

 

5 Marks

 

Question. Why is organic farming favoured these days? Describe the methods employed in the process. 

Answer. I) Chemical fertilizers causes environmental pollution. 

ii) It decreases the fertility and productivity of the soil. 

iii) Framing with chemical fertilizers is expensive.

 

Organic farming uses biopesticides and biofertilizers.

 

i)Biopesticides – a) Baculo viruses – attack harmful insects.

                        b) Bacillus thuringiensis – introduced in crop field. (These bacteria are available sackets as dried spores) which are mixed with water & spread over vulnerable plants.

 

ii) Biofertilizers – a) Cyano bacteria are used in crop field to increase the fertility of soil.

                         b) Azolla is used in crop field which is decomposed & increases the fertility of soil.

 

Question. (i) Three water samples namely river water, untreated sewage water and secondary effluent discharge from a sewage treatment plan were subjected to BOD test. The samples were labeled A, B and C but the lab attendant did not note which BOD is for which water. The BOD values of three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L respectively. Which sample of the water is most polluted? Can you assign the correct label to each, assuming that the river water is relatively clean.

Answer. (1)

(ii) Which is not a tool of Recombinant DNA technology. 

a) Restriction enzyme

b) Vector

c) Bioreactor

 

(iii) Label the following diagram & Identify the selectable markers 

 

 

Answer. I) A- 20 mg /L  Secondary effluent

B – 8 mg/L River water

C – 400 mg/L  Untreated sewage water

ii) Bioreactor

iii)

iv) Role of polymerase – DNA – polymerase is an enzyme used to make copies of DNA making use of the genomic template DNA and the primer.