Q.The bioactive molecule used as an immunosuppressive agent during organ transplant is (A) Tetracyclin (B) Cyclosporin-A (C) Statin (D) Streptomycin
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🔒 Start your 14-day free trial to unlock the full solution →Part (a)Concept understanding — Antibiotic Producing Fungi
Imagine you have a wound that gets infected. Before the 20th century, that infection could easily kill you. Today, we have a weapon against such bacterial infections: antibiotics. The most famous antibiotic, penicillin, comes from a humble source — a fungus.
The intuition is simple: in nature, fungi and bacteria are rivals. They compete for the same food and space. To win this battle, some fungi have evolved a chemical weapon. They produce a substance that kills bacteria or stops them from growing. That substance is an antibiotic. So, an antibiotic-producing fungus is simply a fungus that manufactures a natural chemical to destroy or weaken bacteria.
The precise meaning is this: certain species of fungi (like Penicillium notatum or Cephalosporium acremonium) secrete secondary metabolites — chemicals not essential for their own growth — that are toxic to bacteria. These chemicals interfere with a bacterium's cell wall, its protein-making machinery, or its DNA replication. Because bacterial cells are structurally different from human cells, the antibiotic can often kill the invader without harming us.
Why does this matter? It is the foundation of modern medicine. The discovery of penicillin by Alexander Fleming in 1928 was a turning point. Before antibiotics, a simple scratch could lead to sepsis. Today, antibiotics from fungi save millions of lives every year. They are used to treat pneumonia, tuberculosis, wound infections, and many other bacterial diseases.
Antibiotics are effective only against bacteria, not against viruses (like the common cold or flu). Taking an antibiotic for a viral infection is useless and contributes to a serious problem called antibiotic resistance — where bacteria evolve to become immune to the drug.
Here are the key points to remember:
- Source: The most famous antibiotic-producing fungus is Penicillium, which gives us penicillin. Another is Cephalosporium, which produces cephalosporins. …
Part (b)Concept understanding — Microbial Fermentation Foods
Let’s begin with something you already know. Think of a pot of milk left out in warm weather. After a few hours, it turns sour and thickens into curd. That change is not spoilage in the usual sense — it is a controlled transformation caused by tiny living organisms called microbes. This is the heart of microbial fermentation.
Fermentation is a process in which microorganisms — bacteria, yeast, or moulds — break down organic substances (like sugars) in the absence of oxygen, producing energy for themselves and, as a by‑product, substances that change the food. When we deliberately use this process to make food, we call the result microbial fermented foods.
You have eaten many of them without thinking twice: curd (yogurt), idli and dosa batter, bread, cheese, pickles, vinegar, and even the dark chocolate you might enjoy. Each of these relies on specific microbes doing their work.
The NCERT textbook (Class XII, Biology, Chapter 10: Microbes in Human Welfare) introduces fermented foods under the topic “Microbes in Household Products.” It lists curd, cheese, idli, dosa, and bread as common examples. The key point is that these are not modern inventions — they have been part of Indian and global diets for centuries.
Why does this matter? Because fermentation does three things that are valuable for us:
- Preserves food — The acids or alcohol produced by microbes prevent spoilage by harmful bacteria. Pickles stay edible for months because of lactic acid from fermentation.
- Improves digestibility — Microbes break down complex molecules. Lactose in milk becomes easier to digest in curd; the proteins in soy become more digestible in tempeh.
- Enhances flavour and texture — The tang of yogurt, the airy holes in bread, the umami of soy sauce — all come from fermentation.
Let’s look at a few examples from your daily life, as the NCERT would describe them:
- Curd (yogurt): Milk is boiled and cooled, then a small amount of previous curd (containing Lactobacillus bacteria) is added. The bacteria convert lactose into lactic acid, which thickens the milk and gives it a sour taste.
- Idli and dosa batter: Rice and urad dal are soaked, ground, and left to ferment overnight. Naturally occurring Leuconostoc and other bacteria produce carbon dioxide gas, which makes the batter rise and gives idlis their spongy texture.
- Bread: Baker’s yeast (Saccharomyces cerevisiae) ferments the sugars in dough, releasing carbon dioxide that makes the dough rise. The alcohol produced evaporates during baking.
- Cheese: Milk is curdled using rennet (an enzyme) or acid, then specific bacteria and moulds are added to ripen it. Different microbes give different cheeses their distinct flavours — for example, Penicillium roqueforti gives blue cheese its veins and sharp taste. …
Part (a)
The immunosuppressant used to prevent rejection during organ transplants is Cyclosporin-A, a bioactive molecule produced by the fungus Trichoderma polysporum. (Tetracyclin and Streptomycin are antibiotics; Statin lowers blood cholesterol.) …
Part (a): The immunosuppressive agent used during organ transplants is Cyclosporin-A, made by a fungus — option (B).
Part (b): The Blue revolution means a large increase in fish production — option (B).
Part (a)
After an organ transplant the recipient's immune system tries to reject the foreign organ, so it must be suppressed. The microbial bioactive molecule used for this is Cyclosporin-A, produced by the fungus Trichoderma polysporum. It selectively suppresses the immune response, allowing the graft to survive.
The other options are unrelated:
- (A) Tetracyclin — a broad-spectrum antibiotic.
- (C) Statin — a blood-cholesterol-lowering agent (from Monascus purpureus). …
Showing the 12 most recent of 63 on this concept.
- CBSE 2026Set 57/2/11 markMCQQ.Assertion (A) : Microbes are used for commercial production of alcohol and beverages. Reason (R) : Yeast converts glucose into ethanol and carbon dioxide during fermentation. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation for Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not correct explanation for Assertion (A). (C) Assertion (A) is true, Reason (R) is false. (D) Assertion (A) is false, Reason (R) is true.
›Reveal solutionSolution
Microbes, particularly yeast, are essential for the commercial production of alcohol and beverages because yeast ferments sugars into ethanol and carbon dioxide.
The assertion that microbes are employed in the commercial production of alcohol and beverages is fundamentally correct. For centuries, various microorganisms have been harnessed by humanity for a wide array of industrial processes, and the brewing and distilling industries stand as prime examples. These industries rely heavily on the metabolic activities of specific microbes to transform raw materials into desirable products like beer, wine, whisky, and other alcoholic drinks.
Among these beneficial microbes, yeast holds a paramount position. Yeast, a single-celled fungus, is the primary agent responsible for alcoholic fermentation. This biological process is the cornerstone of alcohol production. Without the action of yeast, the sugars present in grains, fruits, or other plant materials would not be converted into ethanol, the alcohol found in these beverages.
ImportantThe specific species of yeast most commonly used in brewing and distilling is Saccharomyces cerevisiae, often referred to as "brewer's yeast" or "baker's yeast."
The reason provided, stating that yeast converts glucose into ethanol and carbon dioxide during fermentation, accurately describes the biochemical mechanism at play. Fermentation is an anaerobic process, meaning it occurs in the absence of oxygen. In this process, yeast enzymes break down glucose (a simple sugar) into two main products: ethanol (alcohol) and carbon dioxide gas.
- Glucose (a sugar, typically derived from malted barley for beer, grapes for wine, or other carbohydrate sources)
- Yeast enzymes (biological catalysts within the yeast cells) …
- CBSE 2026Set V11 markQ.A small amount of curd added to the fresh milk as ___________.
›Reveal solutionSolution
The small amount of curd added to fresh milk acts as an inoculum/starter of lactic acid bacteria.
A small amount of curd added to fresh milk acts as an inoculum (starter). It contains millions of lactic acid bacteria (LAB), such as Lactobacillus, which multiply at suitable temperatures and convert the milk into curd. During this process the LAB also produce acids that coagulate and partia …
- CBSE 2026Set A1 markMCQQ.Which vitamin content increases due to conversion of milk into curd?(a) Vitamin A(b) Vitamin B2(c) Vitamin C(d) Vitamin B12
›Reveal solutionSolution
Curdling by Lactobacillus increases vitamin B12; the correct option is (d).
When milk is converted into curd, lactic acid bacteria (LAB) such as Lactobacillus grow and multiply, coagulating the milk protein. Besides improving taste and nutritional quality, these bacteria also increase the vitamin B12 content of …
- CBSE 2026Set ANNUAL1 markQ.Fill in the blank: The dough, which is used to make bread, is fermented by yeast called as ______.
›Reveal solutionSolution
Bread dough is leavened by fermentation with the yeast Saccharomyces cerevisiae, whose CO2 production makes the dough rise.
Saccharomyces cerevisiae, commonly called baker's/brewer's yeast, ferments sugars in the dough, releasing carbon dioxide that causes the dough to rise (leavening) and gives bread its …
- CBSE 2026Set ANNUAL1 markQ.What is the botanical name of baker's yeast ?
›Reveal solutionSolution
Baker's yeast, used to leaven bread dough by fermentation, is the fungus Saccharomyces cerevisiae.
Saccharomyces cerevisiae is a unicellular fungus (yeast) that ferments sugars in dough, releasing carbon dioxide gas which causes the dough to rise (leavening) and gives bread its porous texture. The same sp …
- CBSE 2026Set ANNUAL1 markQ.Give one reason how the condition of a patient suffering from myocardial infarction can be improved by administering the bioactive agent Streptokinase.
›Reveal solutionSolution
Streptokinase dissolves the clot blocking the coronary artery, so blood flow to the heart muscle is restored — improving the heart-attack patient.
Myocardial infarction (a heart attack) occurs when a blood clot blocks a coronary artery, cutting off oxygen supply to part of the heart muscle. Streptokinase, produced by the bacterium Streptococcus and modified by genetic engineering, is a clot-buster (thrombolytic agent): it activates plasminogen to plasmin, which digests the fibrin of the clot. By dissolving the clot it removes the b …
- CBSE 2026Set ANNUAL1 markQ.Why are there large holes in 'Swiss Cheese'?
›Reveal solutionSolution
Large holes in Swiss cheese are caused by CO₂ gas released by the bacterium Propionibacterium sharmanii.
Concept: Microbes are used in the processing and production of many dairy foods, including different types of cheese, whose texture, flavour and appearance depend on the specific microbes used. …
- CBSE 2026Set ANNUAL1 markQ.Alexander Fleming, Ernst Chain and Howard Florey were awarded the Nobel Prize in 1945 for the discovery of _________.
›Reveal solutionSolution
The blank is penicillin — the antibiotic from the mould Penicillium notatum whose discovery earned Fleming, Chain and Florey the 1945 Nobel Prize.
In the CBSE/NCERT Microbes in Human Welfare chapter, Alexander Fleming accidentally noticed that the mould Penicillium notatum killed Staphylococcus bacteria in a culture plate. Ernst Chain and Howard …
- CBSE 2026Set ANNUAL1 markQ.Write True or False. Saccharomyces cerevisiae is used in the production of alcohol and bread.
›Reveal solutionSolution
True — Saccharomyces cerevisiae is used both to produce alcohol (brewer's yeast) and to make bread rise (baker's yeast).
In the CBSE/NCERT Microbes in Human Welfare chapter, Saccharomyces cerevisiae carries out fermentation of sugars:
- In brewing/wine-making it produces ethanol (alcohol) and CO₂. …
- CBSE 2025Set A1 markMCQQ.First antibiotic is obtained from which micro organism?(a) Penicillium(b) Streptococcus(c) Salmonella typhimurium(d) Vibrio cholerae
›Reveal solutionSolution
Penicillin, the first antibiotic, was obtained from the fungus Penicillium.
In 1929, Alexander Fleming observed that a mould contaminating his bacterial culture plate (Staphylococcus) had inhibited bacterial growth around it. The mould was identified as Penicillium notatum, and the antibacterial substance it secreted was named penicillin — the world's first antibiotic. It was later mass-produced by Er …
- CBSE 2025Set A1 markQ.Match the correct pair and write the match for 'Toddy'. Column I:(i) Apomixis(ii) Darwin(iii) Toddy(iv) Agarose(v) Detritivorous. Column II:(a) Galapagos Islands(b) Southern India(c) Sea weeds(d) Earthworm(e) Grass family.
›Reveal solutionSolution
Toddy matches with (b) Southern India, where it is a traditional fermented drink.
Toddy is a mildly alcoholic traditional beverage of Southern India, prepared by natural fermentation of the sap (sugary exudate) tapped from palm trees, using naturally occurring yeasts. It is a classic NCERT example of microbes (yeast) being used by humans in the production of trad …
- CBSE 2025Set ANNUAL1 markQ.By increasing of which vitamin the nutritional quality of curd is improves as compared to milk?
›Reveal solutionSolution
Lactic acid bacteria that convert milk into curd increase the vitamin B12 content of curd compared to milk.
During curd (dahi) formation, lactic acid bacteria (LAB, e.g., Lactobacillus) multiply in milk and, besides lowering pH and improving its keeping quality/flavour, they also enhance its nutritional valu …
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