Page 1 :
(Chapter — 10) (Microbes in Human Welfare), (Class - XII), , Question 1:, , Bacteria cannot be seen with the naked eyes, but these can be seen with the, help of a microscope. If you have to carry a sample from your home to your, biology laboratory to demonstrate the presence of microbes under a, microscope, which sample would you carry and why?, , Answer 1:, , Curd can be used as a sample for the study of microbes. Curd contains, numerous lactic acid bacteria (LAB) or Lactobacillus. These bacteria, produce acids that coagulate and digest milk proteins. A small drop of curd, contains millions of bacteria, which can be easily observed under a, microscope., , Question 2:, , Give examples to prove that microbes release gases during metabolism., Answer 2:, , The examples of bacteria that release gases during metabolism are:, , > Bacteria and fungi carry out the process of fermentation and during, this process, they release carbon dioxide. Fermentation is the process of, converting a complex organic substance into a simpler substance with the, action of bacteria or yeast. Fermentation of sugar produces alcohol with the, release of carbon dioxide and very little energy., , nithwwt, , Glucose —{ alcohol + energy +CO,, , > The dough used for making idli and dosa gives a puffed appearance., This is because of the action of bacteria which releases carbon dioxide. This, CO; released from the dough gets trapped in the dough, thereby giving it a, , puffed appearance., , Question 3:, , In which food would you find lactic acid bacteria? Mention some of their, useful applications., , Answer 3:, , Lactic acid bacteria can be found in curd. It is this bacterium that promotes, the formation of milk into curd. The bacterium multiplies and increases its, number, which converts the milk into curd. They also increase the content, of vitamin B,2 in curd., , Lactic acid bacteria are also found in our stomach where it keeps a check on, the disease-causing micro-organisms.
Page 2 :
Question 4:, Name some traditional Indian foods made of wheat, rice and Bengal gram, (or their products) which involve use of microbes., Answer 4:, > Wheat:, Product: Bread, cake, etc., > Rice:, Product: Idli, dosa, > Bengal gram:, Product: Dhokla, Khandvi, , Question 5:, , In which way have microbes played a major role in controlling diseases, caused by harmful bacteria?, , Answer 5:, , Several micro-organisms are used for preparing medicines. Antibiotics are, medicines produced by certain micro-organisms to kill other diseasecausing micro-organisms, These medicines are commonly obtained from, bacteria and fungi. They either kill or stop the growth of disease-causing, micro-organisms. Streptomycin, tetracycline, and penicillin are common, antibiotics, Penicillium notatum produces chemical penicillin, which checks, the growth of staphylococci bacteria in the body. Antibiotics are designed, to destroy bacteria by weakening their cell walls. As a result of this, weakening, certain immune cells such as the white blood cells enter the, bacterial cell and cause cell lysis. Cell lysis is the process of destroying cells, such as blood cells and bacteria., , Question 6:, , Name any two species of fungus, which are used in the production of the, antibiotics., , Answer 6:, , Antibiotics are medicines that are produced by certain micro-organisms to, kill other disease-causing micro-organisms. These medicines are commonly, obtained from bacteria and fungi., , The species of fungus used in the production of antibiotics are:
Page 3 :
Question 7:, , What is sewage? In which way can sewage be harmful to us?, , Answer 7:, , Sewage is the municipal waste matter that is carried away in sewers and, drains. It includes both liquid and solid wastes, rich in organic matter and, microbes. Many of these microbes are pathogenic and can cause several, water- borne diseases. Sewage water is a major cause of polluting drinking, water. Hence, it is essential that sewage water is properly collected, treated,, , and disposed., , Question 8:, What is the key difference between primary and secondary sewage, treatment?, , , , , , Answer 8:, , 1. It is a mechanical process 1. It is a biological process, involving the removal of coarse involving the action of, , ____ Solid materials. microbes., , |2. It is inexpensive and relatively 2. It is a very expensive and, less complicated. complicated process., , Question 9:, , Do you think microbes can also be used as source of energy? If yes, how?, Answer 9:, Yes, microbes can be used as a source of energy. Bacteria such as Methane, , bacterium is used for the generation of gobar gas or biogas., , The generation of biogas is an anaerobic process in a biogas plant, which, consists of a concrete tank (10-15 feet deep) with sufficient outlets and, inlets. The dung is mixed with water to form the slurry and thrown into the, tank. The digester of the tank is filled with numerous anaerobic methaneproducing bacteria, which produce biogas from the slurry. Biogas can be, removed through the pipe which is then used as a source of energy, while, the spent slurry is removed from the outlet and is used as a fertilizer.
Page 4 :
Question 10:, , Microbes can be used to decrease the use of chemical fertilisers and, pesticides. Explain how this can be accomplished., , Answer 10:, , Microbes play an important role in organic farming, which is done without, the use of chemical fertilizers and pesticides. Bio-fertilizers are living, organisms which help increase the fertility of soil. It involves the selection, of beneficial micro-organisms that help in improving plant growth through, the supply of plant nutrients. Biofertilizers are introduced in seeds, roots, or, soil to mobilize the availability of nutrients. Thus, they are extremely, beneficial in enriching the soil with organic nutrients. Many species of, bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen., Rhizobium is a symbiotic bacteria found in the root nodules of leguminous, plants. Azospirillium and Azotobocter are free living nitrogen-fixing, bacteria, whereas Anabena, Nostoc and Oscillitoria are examples of, nitrogen-fixing cyanobacteria. Bio-fertilizers are cost effective and ecofriendly., , Microbes can also act as bio-pesticides to control insect pests in plants. An, example of bio-pesticides is Bacillus thuringiensis, which produces a toxin, that kills the insect pests. Dried bacterial spores are mixed in water and, sprayed in agricultural fields. When larvae of insects feed on crops, these, bacterial spores enter the gut of the larvae and release toxins, thereby it., Similarly, Trichoderma are free living fungi. They live in the roots of higher, plants and protect them from various pathogens. Baculoviruses is another, bio-pesticide that is used as a biological control agent against insects and, , other arthropods., Question 11:, , Three water samples namely river water, untreated sewage water and, secondary effluent discharged from a sewage treatment plant were subjected, to BOD test. The samples were labelled A, B and C; but the laboratory, attendant did not note which was which. The BOD values of the 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 the river water is relatively clean?, Answer I1:, , Biological oxygen demand (BOD) is the method of determining the amount, of oxygen required by micro-organisms to decompose the waste present in
Page 5 :
the water supply. If the quantity of organic wastes in the water supply is, high, then the number of decomposing bacteria present in the water will also, be high. As a result, the BOD value will increase., , Therefore, it can be concluded that if the water supply is more polluted, then, it will have a higher BOD value. Out of the above three samples, sample C, is the most polluted since it has the maximum BOD value of 400 mg/L., After untreated sewage water, secondary effluent discharge from a sewage, treatment plant is most polluted. Thus, sample A is secondary effluent, discharge from a sewage treatment plant and has the BOD value of 20 mg/L,, while sample B is river water and has the BOD value of 8 mg/L., , Hence, the correct label for each sample is:, , , , f a 4 ees iat, 8 mg/L River water, 400 mg/L —_—_ Untreated sewage water, , Question 12:, Find out the name of the microbes from which Cyclosporin A (an, immunosuppressive drug) and Statins (blood cholesterol lowering agents), , are obtained., , Answer 12:, , , , , Blood cholesterol lowering Monascus purpureus, agent, , Question 13:, Find out the role of microbes in the following and discuss it with your, , teacher., , (a) Single cell protein (SCP), , (b) Soil, , Answer 13:, , (a) Single cell protein (SCP), , A single cell protein is a protein obtained from certain microbes, which, forms an alternate source of proteins in animal feeds. The microbes involved, , in the preparation of single cell proteins are algae, yeast, or bacteria. These
