Important Questions Class 12 Biology Chapter 10

Important Questions for CBSE Class 12 Biology Chapter 10 – Microbes in Human Welfare

These Class 12 Biology Chapter 10 Important Questions are based on CBSE NCERT books. Students appearing for Class 12 exams can take a quick revision from these questions, which will be helpful to the students in scoring good marks and passing with flying colours.

CBSE Class 12 Biology Chapter 10 Important Questions

Access NCERT Solutions for Class 12 Biology Chapter 10 – Microbes in Human Welfare

Very Short Answer Questions

1. When a small amount of curd is added to milk, it converts into curd. How? What is the nutritional quality that’s added to the curd?

Ans. Lactic acid bacteria are detected in a small amount of curd. The lactic acid bacteria increase and turn the milk into curd. Vitamin B12 enhances nutritional quality.

2. In sewage treatment plants, the secondary treatment is called biological treatment. Why?

Ans. In this treatment, the organic wastes are digested by particular bacteria in the presence of microorganisms and water.

3. During World War II, Wonder Drug, an antibiotic, was used to treat the soldiers of America. Name the scientist who discovered it and the drug name.

Ans. Alexander Fleming discovered penicillin.

4. Why are the fruit juices in bottles brought from the market clearer than those made at home?

Ans. To clarify bottle juices, proteases and pectinase are used.

5. Alexander Fleming discovered penicillin, but other scientists did not know its potential as an effective antibiotic. Name the two scientists.

Ans. Ernest Chain and Howard Florey.

6. In making toddy which plant’s sap is used? What is the process involved in making this?

Ans. Palm tree sap is used in making toddy, and the fermentation process is involved in making this.

7. What is the clinical usage of cyclosporin, a composition?

Ans. Cyclosporin is a composition that is used as an immunosuppressive drug during organ transplantation for any human being.

8. What are the pests that ladybirds & dragonflies help to get rid of?

Ans. Aphids control ladybird beetles, and mosquitoes control dragonflies.

9. Prove with an example that microbes release gases during metabolism.

Ans. Puffed dough and bread are perfect examples of bacteria releasing gases during metabolism.

10. Describe Interferons.

Ans. Interferons are proteins released by the cells concerning the viral infection, which help fight against viral infection.

11. Which is the enzyme used as a clot buster for removing a blood clot from patients’ blood vessels?

Ans. Streptokinase is the enzyme used as a clot buster for removing a blood clot from patients’ blood vessels.

12. What is LAB in biology?

Ans. Lactic Acid Bacteria are known as LAB in biology.

13. Name two free-living nitrogen-fixing bacteria.

Ans. Two free-living nitrogen bacteria are Azotobacter and Azospirillum.

14. What are the gases produced during the secondary treatment of sewage?

Ans. Hydrogen sulphide, methane, and carbon dioxide are the gases produced during the secondary treatment of sewage.

15. Which is the organism used in dough while making bread?

Ans. Saccharomyces cerevisiae is the organism used in dough while making bread.

These are references to CBSE additional questions, CBSE revision notes, and CBSE sample papers from the CBSE syllabus. Students can also refer to CBSE’s past years’ question papers.

Short Answer Questions

1. Which are the two alcoholic drinks produced in these ways? (i) By distillation and (ii) Without distillation.

Ans. (i) Whiskey, Brandy and Rum are produced by distillation. (ii) Without distillation, wine and beer are produced.

2. Lactic Acid Bacteria is used for the conversion of milk into curd. What are the two other functions of Lactic Acid Bacteria useful to humans?

Ans. (i) In the human gut, vitamin B12 is synthesised by Lactic Acid Bacteria. (ii) When Lactic Acid Bacteria is present in the human stomach, it inhibits the growth of dangerous microorganisms.

3. Explain how mycorrhizae function as biofertilizers.

Ans. The fungi connected with plant roots are known as mycorrhizae. Many species of the Glomus genus form mycorrhizae. These fungal symbionts collect water and minerals from the soil and pass them to the plant.

These are Class 12 Biology Chapter 10 Important Questions. The important questions in Class 12 Biology Chapter 10 are very important for students. Formulas are to be remembered by students for scoring good marks. Class 12 Biology Chapter 10 Important Questions are discussed in this article.

Short Answer Questions

1. Explain the Biochemical Oxygen Demand (BOD) test. This test is performed at what stage of sewage treatment? The Biochemical Oxygen Demand level of three samples of water labelled A, B, and C are 30 mg/L, 10 mg/L, and 500 mg/L, respectively. Out of these, which sample of water is most polluted?

Ans. (i) Biochemical Oxygen Demand test determines how quickly microorganisms in a water sample absorb oxygen. (ii) Biological treatment or secondary treatment (iii) Sample C is the most polluted of the three water samples, as it has the greatest Biochemical Oxygen Demand level.

2. Describe the scientific name of the bacterium that ferments malted grains and fruit juices.

Ans. Saccharomyces cerevisiae, usually known as brewer’s yeast, is the bacterium responsible for the fermentation of malted cereals and fruit juices.

3. What are statins? Which microorganism produces this substance? Why is it medically important?

Ans. Statins are produced by Monascupurpureus, which are cholesterol-lowering drugs. They completely block the enzymes involved in cholesterol production.

4. State the process involved in sewage treatment.

Ans. The technique performed for the treatment of sewage waste is as follows.

(i) Primary Treatment: In this stage, the suspended materials are physically separated in settling tanks to reduce BOD. The raw sewage is routed out into big open tanks concerning anaerobic digestion to remove the solid fraction.

(ii) Secondary Treatment: The second stage of secondary treatment relies on microbial activity, which is either anaerobic or aerobic. The techniques involved in this treatment are as follows:

• Aeration process
• Sand filters for filtration
• Application of oxidation ponds

After drying, the sludge collected after secondary treatment is disposed of, and the efferent is used for tertiary treatment.

(iii) Tertiary Treatment: The third tertiary treatment stage comprises chemical treatment, which eliminates inorganic chemicals and pathogenic microorganisms. The most common disinfection procedure is chlorination.

5. Explain biogas. How is biogas produced and which are microbes invaded in biogas production?

Ans. Gas produced by anaerobic fermentation of waste biomass is known as biogas. Biogas comprises methane, CO2, hydrogen, nitrogen, oxygen, and hydrogen sulphide. There are microbes involved in the production of biogas, such as:

• Hydrolytic bacteria such as clostridium, cellulosomes, etc.
• Bacteria which produce hydrogen sulphide, such as  wolfei
• A methanogenic bacteria example is methanobacterium omelianskii

A concrete tank is used for feeding Biogas plants. The biogas slurry is covered with a floating cover, which rises when the gas is created in the tank. Output in a biogas plant connects to a pipe that distributes biogas to surrounding residences. Microbes transform the part of biodegradable organic solid waste into energy in the form of biogas and humus while producing biogas.

CO + H2O -> CO2 + H2

CO2 + 4H2 -> CH4 + 2H2O

CH3OH -> CH4 + 02

6. To decrease the use of chemical fertilisers and pesticides, microbes are used. How is this done? Explain.

Ans. In modern society, to combat plant diseases, chemicals are used. The chemicals used are poisonous and harmful to humans and the environment. In farming, a pest control method depends on natural predation, like controlling butterflies, caterpillars, and other insects. Bacillus thuringiensis is a bacteria provided as dried spores in sachets to be mixed with water and then sprayed onto sensitive plants such as brassicas, where larvae are consumed. The toxin is then released in the intestines of larvae by killing them. The bacterial sickness will kill the caterpillar but does not harm other insects.

7. Biofertilizers enrich the fertility of the soil. How? How do cyanobacteria act as a biofertilizer?

Ans. Microorganisms engage biological channels to improve the fertility of the soil for optimal crop development, and they are known as Biofertilizers. These microorganisms boost crop output in many ways, which are mentioned below:

(i) Through the absorption of phosphorus

(ii) Removal of nitrogen from the atmosphere

(iii) Insoluble fertiliser solubilization

(iv) The growth of plants is promoted

(v) By allowing plant remnants to decompose

A cyanobacterium known as Anabaena, found in the cavity of the fern leaf, Azolla, fixes nitrogen from the air we breathe and excretes nitrogenous compounds into the cavity.

8. What is the difference between primary sludge and activated sludge? What changes in the sludge are carried out in an anaerobic sludge disaster? What is the composition of biogas in the sewage treatment plant?

Ans. Primary sludge is made of solids, such as soil and small stones that settle in the tank during sewage treatment. Activated sludge is the sediment of bacterial flocs in the settling tank following biological treatment. Slime and fungal filaments bind bacteria together to form flocs. From the activated sludge, a portion is used as inoculum in the aeration tank, and the remaining is sent to the anaerobic sludge disaster, a big tank. Other than this, the bacteria that grow anaerobically in this tank consume the bacteria and fungus in the sludge.

Biogas is the mixture of methane, hydrogen, and carbon dioxide created in sewage treatment plants.