VBQs Class 12 Biology Microbes in Human Welfare
Very Short Answer Type Questions
Question. Why do we add an inoculum of curd to milk for curdling it ?
Answer : Inoculum contains Lactobacilli which curdles milk into curd with lactic acid. Lactobacillus converts lactose sugar of milk into lactic acid which causes coagulation and partial digestion of milk protein casein. As a result, milk gets changed into curd.
Question. Give the scientific name of the source organism from which the first antibiotic was produced.
Answer : Penicillium notatum.
Question. Name the metabolic pathway associated with the rising of dough in making bread. What makes the dough rise ?
Answer : Metabolic pathway : Alcoholic fermentation by yeast. CO2 produced in this process is responsible for rising of dough.
Question. Milk start to coagulate when lactic acid bacteria are added to warm milk as a starter. Mention any other two benefits LAB provide.
Answer : Besides curdling of milk the lactic acid bacteria are beneficial to us in following ways :
(i) They improve the nutritional quality of curd by producing Vitamin B12.
(ii) They help in inhibiting the development of disease causing microorganism in the gut.
Question. Name the group of organisms and the substrate that act to produce biogas.
Answer : Name of the group of organisms-Methanogens Substrate-Cellulosic material, cow dung and agricultural waste.
Short Answer Type Questions
Question. List the events that lead to biogas production from waste water whose BOD has been reduced significantly.
Answer : Sedimentation of flocs to form activated sludge, sludge pumped to anaerobic sludge digester, growth of anaerobic bacteria, digestion of sludge by bacteria to release biogas.
Detailed Answer :
Events that lead to biogas production from waste water with reduced BOD are:
(i) Once the BOD of waste water is significantly reduced, the effluent is passed into a settling tank for sedimentation.
(ii) From settling tank, the major part of sedimented material called activated sludge (bacterial flocs) is pumped into large tanks called anaerobic sludge digester and a small part is pumped back into aeration tank to serve as inoculum.
(iii) In these tanks, the sludge is anaerobically digested by bacteria and fungi, biogas is produced which is a mixture of methane, hydrogen sulphide and CO2. The biogas can be used as a source of energy as it is inflammable.
Question. Explain the different steps involved during primary treatment phase of sewage.
Answer : Physical removal of particles (large and small), by filtration and sedimentation, forming primary sludge / sedimented solids, forming effluent (supernatant) for secondary treatment.
Detailed Answer :
Primary treatment : The primary phase of sewage treatment involves physical removal of particles by filtration and sedimentation. Different steps involved during the primary treatment are as follows :
Initially, floating debris of sewage water is removed by sequential filtration through many screens.
Then, grit (soil + small pebbles) is removed by sedimentation in large settling tanks. The remaining solid particles, which have settled down form the sludge while the supernatant forms the effluent.
Effluent is then taken for secondary treatment.
Question. Explain the function of ‘‘anaerobic sludge digester’’ in a sewage treatment plant.
Answer : In anaerobic sludge digester, the anaerobic bacteriathe methanogen digest the flocs of bacteria and fungi in activated sludge and produce methane along with H2S and CO2 i.e. biogas which is a source of energy as it is inflammable.
Question. Distinguish between the roles of flocs and anaerobic sludge digesters in sewage treatments.
|S.No.||Flocs||Anaerobic Sludge Digester|
|(i)||Breakdown organic matter aerobically.||Breakdown organic matter anaerobically.|
|(ii)||Breaks down organic matter present in primary effluent.||Breaks down organic matter present in secondary effluent.|
|(iii)||They do not produce biogas.||They produce biogas (mixture of methane,|
H2S and CO2).
Detailed Answer :
Flocs are the mixtures of heterotrophic aerobic microbes that grow in aeration tank during secondary treatment of effluent. They consume a major part of the organic matter of the effluent. In anaerobic sludge digesters, anaerobic bacteria grow and digest the rest of the organic compounds and produce biogas.
Question. Name the source of cyclosporin-A. How does this bioactive molecules function in our body ?
Answer : Cyclosporin-A is produced by the fungus Trichoderma polysporum. Cyclosporin-A is antifungal, antiinflamatory and used as an immunosuppressant.
It is able to suppress the immune system enough so that organs and tissues, not original to the body, can be transplanted.
Question. State the use of :
(i) Trichoderma with respect to organ transplant and
(ii) Nucleopolyhedrovirus with respect to pest management.
Answer : (i) Trichoderma : It produces a bioactive molecule called cyclosporin A, which is used as an immunosuppressive agent in organ transplant.
(ii) Nucleopolyhedrovirus : Belongs to the family baculoviruses which are used as biocontrol agents.
These viruses attack insects and they are excellent for species-specific, narrow-spectrum insecticidal applications. They are quite specific and therefore do not have any negative impact on non target organisms, thus making them useful in overall integrated pest management programme.
Question. Why are some molecules called bioactive molecules ? Give two examples of such molecules.
Give the scientific name of microbes from which cyclosporin-A and statin are obtained. Write one medical use of each one of these drugs.
Answer : Some molecules are produced by certain living organism and have ability to perform functions and modify metabolism in body of other living organims are known as bioactive molecule.
Examples of bioactive molecules are :
(i) Cyclosporin-A : It is used as an immunosuppressive agent in organ-transplant patients. It is produced by Trichoderma polysporum.
(ii) Statins : Statins are produced by the yeast Monascus purpureus and have been commercialized as cholesterol-lowering agents.
Question. Name the first antibiotic discovered and by whom.
Answer : Penicillin, Alexander Fleming.
Question. (i) A patient who had an organ transplant was given cyclosporin – A. Mention the microbial source and state the reason for administration of this bioactive molecule.
(ii) Bottled fruit juices bought from the market are clearer as compared to those made at home. Give reason.
Answer : (i) Source – Trichoderma polysporum.
Reason – Immuno suppressive agent.
(ii) They are clarified by pectinases and proteases.
Question. Name the microbes that help the production of the following products commercially :
(ii) Citric acid
(iv) Butyric acid
Answer : (i) Monascus purpureus
(ii) Aspergillus niger
(iii) Penicillium notatum
(iv) Clostridium butyricum
Question. Cow dung and water is mixed and this slurry is fed into the biogas plant for digestion by microbes.
The person performing the process shares that there is no need to provide inoculum for it, why?
What is the role of microbes at the source? Under which condition will they be most active and effective ?
Answer : Methanogens are present in cow dung.
Breakdown of cellulose.
Detailed Answer :
If the slurry of cow dung and water is fed into the biogas plant, there is no need to provide inoculum as the cow dung or excreta of cattle in itself contain a large number of anaerobic methanogenic bacteria.
Therefore, the slurry (cow dung and water) can be used for generation of biogas.
These bacteria breakdown the cellulosic material present in the rumen of cattle anaerobically and produce large amount of methane along with CO2 and H2S.
Question. Explain the changes that can be observed in the characteristics of river water when sewage is discharged into it and a few weeks after the discharge with respect to :
(i) level of dissolved oxygen
(ii) population of fresh water organisms.
|Criteria / Time of Sewage discharged||When sewage is discharged||Few weeks after discharge|
|(i) Level of dissolved oxygen||Microorganisms involved in biodegradation of organic matter consume a lot of oxygen, resulting in sharp decline in dissolved oxygen.||Level of dissolved oxygen \|
increases as sewage decreases.
|(ii) Population of fresh water|
|Decline in dissolved oxygen causes mortality of fresh water organisms.||Reappearance of population|
fresh water organisms.
Question. State the medicinal value and the bioactive molecules produced by Streptococcus, Monascus and Trichoderma.
Answer : Streptococcus : It produces Streptokinase enzyme that is used to dissolve clots formed in the blood vessels.
Monascus (Yeast) : It produces statins that help in lowering blood cholesterol levels.
Trichoderma (Fungus) : It produces cyclosporin A that is used as an immunosuppressant agent in organ transplantation. It inhibits activation of T-cells and thus prevents rejection of transplants.
Question. What are Methanogens ? Name the animals they are present in and the role they play there.
Answer : Methanogens are the bacteria which grow anaerobically on cellulosic material and produce large amount of methane along with CO2 and H2S.
(i) Present in cattle (rumen) a part of stomach.
(ii) They help in
(a) Breaking down of cellulose present in food of cattle.
(b) Nutrition of animal for digestion of cellulose.
The excreta of cattle is rich in these bacteria (methanogens) and therefore can be used for generation of biogas.
Question. Identify a, b, c, d, e and f in the following table :
Answer : (i) (a) Streptokinase.
(b) ‘Clot buster‘ for removing clots from the blood vessels (of patients who have undergone myocardial infarction leading to heart attack) / clot buster enzyme.
(ii) (c) Cyclosporin.
(d) Trichoderma polysporum.
(iii) (e) Monascus purpureus (yeast).
(f) Blood cholesterol lowering agent.
Question. Secondary treatment of the sewage is also called Biological treatment. Justify this statement and explain the process.
Answer : It involves biological organism such as aerobic microbes / bacteria and fungi to digest / consume organic waste.
Primary effluent is passed into aeration tank where vigorous growth of aerobic mircobes (flocs) take place, BOD reduced (microbes consume major part of organic matter), effluent is passed to settling tank where flocs sediment to produce activated sludge, sludge is pumped to anaerobic sludge digester to digest bacteria and fungi.
Question. The three microbes are listed below. Name the product produced by each one of them and mention their use.
(a) Aspergillus niger
(b) Trichoderma polysporum
(c) Monascus purpureus
Answer : (a) Aspergillus niger – Citric Acid, natural preservative / flavouring agent.
(b) Trichoderma polysporum – Cyclosporin A , immunosuppressive agent.
(c) Monascus purpureus – Statin, blood cholesterol lowering agent.
Question. Microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel. Write how this happens ?
Answer : Heterotrophic microbes naturally present in sewage are used. Vigorous growth of aerobic microbes as flocs uses organic matter in effluent and reduce BOD of waste water. Other kinds of bacteria grow in it anaerobically and digest the bacteria and fungi called flocs (masses of bacteria associated with fungal filaments). As they digest flocs, a mixture of CH4, H2S, and CO2 or biogas is evolved, which can be used as a fuel.
Question. Name the two different categories of aerobic microbes naturally occurring in sewage water.
Explain their role in cleaning sewage water into usable water.
Answer : The two different categories of aerobic microbes naturally occurring in sewage water are bacteria and fungi. The two together forms flocs a mesh like structure.
The following three treatments are carried out for purifying sewage water:
(i) Primary treatment :
(a) Separation of large debris.
(b) Sedimentation in tanks.
(ii) Secondary treatment :
(a) Waste water is pumped in shallow stabilization or oxidation ponds, where microbes oxidize its organic matter.
(b) The process results in release of CO2 and formation of sludge.
(c) Sludge is continuously aerated further for its oxidation.
(iii) Tertiary treatment :
(a) Removal of turbidity in waste water caused by the presence of nutrients (N2, P, etc.) in dissolved organic matter, metals or pathogens.
(b) It involves chemical oxidation by strong oxidising agents such as chlorine gas, perchlorate salts, ozone gas, UV radiations.
The diagram above is that of a typical biogas plant. Explain the sequence of events occurring in a biogas plant. Identify a, b and c.
Answer : Bio wastes are collected and a slurry of dung is fed.
A floating cover having gas outlet is placed over slurry which keeps on rising as the gas is produced in the tank, the spent slurry is removed through another outlet and may be used as fertilizer.
(a) sludge loader.
(b) gas holder / CH4 and CO2 .
(c) dung and water.
Question. Mention the product and its use produced by each of the microbes listed below :
(iii) Saccharomyces cerevisiae
Answer : (i) Streptokinase, clot buster / dissolves clot from blood vessels.
(ii) Lactic acid, coagulates milk / partial digestion of milk proteins casein.
(iii) Ethyl alcohol + CO2, ferments dough to make bread / idli.
Long Answer Type Questions
Question. Draw labelled sketch of a typical biogas plant.