Samacheer Kalvi Class 12 Bio Zoology Solutions Chapter 8 Microbes in Human Welfare

 

Question 1. Which of the following microorganism is used for production of citric acid in industries?
(a) Lactobacillus bulgaris
(b) Penicillium citrinum
(c) Aspergillus niger
(d) Rhizopus nigricans
Answer: (c) Aspergillus niger
In simple words: The fungus Aspergillus niger is commonly used to make citric acid in factories. It helps turn sugar into this important acid.

🎯 Exam Tip: Remember specific microbes and the industrial products they help create, as this is a common topic in microbiology.

 

Question 2. Which of the following pair is correctly matched for the product produced by them?
(a) Acetobacter aceti - Antibiotics
(b) Methanobacterium - Lactic acid
(c) Penicilium notatum - Acetic acid
(d) Saccharomyces cerevisiae - Ethanol
Answer: (d) Saccharomyces cerevisiae - Ethanol
In simple words: Saccharomyces cerevisiae, which is a type of yeast, is correctly matched with ethanol because it produces ethanol through fermentation. This yeast is important in brewing and alcohol production.

🎯 Exam Tip: Pay close attention to the specific microorganisms and their corresponding products, as small differences can lead to incorrect answers in matching questions.

 

Question 3. The most common substrate used in distilleries for the production of ethanol is
(a) Soyameal
(b) Groundgram
(c) Molasses
(d) Corn meal
Answer: (c) Molasses
In simple words: Molasses is often used in places where alcohol is made because it is a cheap and sugary raw material. This sugary liquid, a byproduct of sugar refining, is perfect for yeast to ferment into ethanol.

🎯 Exam Tip: Knowing the common raw materials (substrates) for industrial fermentation processes is key to understanding microbial applications.

 

Question 4. Cry toxins obtained from Bacillus thuringiensis are effective against for ...........
(a) Mosquitoes
(b) Flies
(c) Nematodes
(d) Bollworms
Answer: (d) Bollworms
In simple words: The natural poisons made by the Bacillus thuringiensis bacteria are very good at killing bollworms. These toxins are used in some crops to protect them from insects, acting as a natural pest control.

🎯 Exam Tip: Understand that Bt toxins are specific to certain insect pests, making them valuable in targeted biological pest control.

 

Question 5. Cyclosporin - A is an immunosuppressive drug produced from ............
(a) Aspergillus niger
(b) Manascus purpureus
(c) Penicillium notatum
(d) Trichoderma polysporum
Answer: (d) Trichoderma polysporum
In simple words: Cyclosporin-A, a medicine that lowers the body's immune response, comes from a fungus called Trichoderma polysporum. This drug is often used to stop the body from rejecting new organs after a transplant.

🎯 Exam Tip: Identify the source organisms for important bioactive molecules, especially those with medical applications like immunosuppressants.

 

Question 6. Which of the following bacteria is used extensively as a bio-pesticide?
(a) Bacillus thuringiensis
(b) Bacillus subtilis
(c) Lactobacillus acidophilus
(d) Streptococcus lactis
Answer: (a) Bacillus thuringiensis
In simple words: Bacillus thuringiensis is a type of bacteria widely used as a natural pesticide. It creates toxins that specifically harm certain insects, helping to protect crops without using harsh chemicals.

🎯 Exam Tip: Bacillus thuringiensis (Bt) is a key example of a microbe used for biological control, so remember its name and function.

 

Question 7. Which of the following is not involved in nitrogen fixation?
(a) Pseudomonas
(b) Azotobacter
(c) Anabaena
(d) Nostoc
Answer: (a) Pseudomonas
In simple words: Pseudomonas bacteria do many things, but they are not known for fixing nitrogen, which is the process of turning nitrogen gas from the air into forms plants can use. Other bacteria like Azotobacter, Anabaena, and Nostoc are known nitrogen fixers that help enrich soil.

🎯 Exam Tip: Distinguish between microbes that perform nitrogen fixation and those that do not, as their roles in soil health are distinct.

 

Question 8. CO2 is not released during
(a) Alcoholic fermentation
(b) Lactate fermentation
(c) Aerobic respiration in animals
(d) Aerobic respiration in plants
Answer: (b) Lactate fermentation
In simple words: When cells make energy through lactate fermentation, like in your muscles during intense exercise, they do not release carbon dioxide. In contrast, alcoholic fermentation and aerobic respiration processes all produce carbon dioxide.

🎯 Exam Tip: Understand the byproducts of different types of respiration and fermentation to correctly identify when CO2 is produced and when it is not.

 

Question 9. The purpose of biological treatment of waste water is to ...........
(a) Reduce BOD
(b) Increase BOD
(c) Reduce sedimentation
(d) Increase sedimentation
Answer: (a) Reduce BOD
In simple words: The main goal of using living things like bacteria to clean wastewater is to lower its Biological Oxygen Demand (BOD). A lower BOD means there is less organic waste that needs oxygen to break down, which makes the water safer for the environment.

🎯 Exam Tip: Remember that reducing BOD is a primary objective in wastewater treatment, as it indicates cleaner water with less organic pollution.

 

Question 10. The gases produced in anaerobic sludge digesters are ...........
(a) Methane, oxygen and hydrogen sulphide.
(b) Hydrogen sulphide, methane and sulphur dioxide.
(c) Hydrogen sulphide, nitrogen and methane.
(d) Methane, hydrogen sulphide and CO2
Answer: (d) Methane, hydrogen sulphide and CO2
In simple words: When sludge is broken down without air in special tanks, the main gases produced are methane, which can be used as fuel, along with hydrogen sulfide and carbon dioxide. These gases are often called biogas and are a valuable energy source.

🎯 Exam Tip: Recall the key components of biogas (methane, CO2, H2S) which are formed during anaerobic digestion.

 

Question 11. How is milk converted into curd? Explain the process of curd formation?
Answer: Milk turns into curd because of special bacteria called LAB (Lactic Acid Bacteria). These bacteria grow in the milk and break down a milk protein called casein. When you add a tiny bit of old curd, known as a starter or inoculum, to fresh milk, it brings millions of these Lactobacilli bacteria. If kept at a warm temperature (below 40°C), these bacteria multiply fast and change the milk into curd. Curd is better for you than milk because it has more good organic acids and vitamins. This process improves the digestibility of milk proteins.
In simple words: Bacteria in milk digest its protein and turn it into curd. A small amount of old curd helps start this process by adding good bacteria that multiply and thicken the milk.

🎯 Exam Tip: When explaining biological processes, highlight the specific microorganisms involved, the chemical changes they cause, and the optimal conditions for the process.

 

Question 12. Give any two bioactive molecules produced by microbes and state their uses.
Answer:

Microbes produce many useful bioactive molecules, including enzymes and therapeutic agents. Lipases are enzymes that break down fats and are effective in removing grease and oil. Streptokinase is a powerful enzyme used in medicine to dissolve dangerous blood clots.
In simple words: Microbes make special things like lipases (which clean clothes by breaking down oils) and streptokinase (which doctors use to dissolve blood clots). These molecules are very helpful for daily life and medicine.

🎯 Exam Tip: Focus on linking specific microbial products to their practical applications, especially in medicine and industrial processes.

 

Question 13. What is biological oxygen demand?
Answer: Biological Oxygen Demand, or BOD, measures how much oxygen would be used up if all the organic material in one liter of water was broken down by bacteria. This means that a high BOD level in wastewater shows a lot of pollution. Sewage water is cleaned until its BOD level drops significantly. The higher the BOD of wastewater, the more harmful it is to the environment because it uses up a lot of oxygen that aquatic life needs. Thus, reducing BOD is a critical step in wastewater treatment.
In simple words: BOD tells us how much oxygen bacteria need to break down all the waste in water. High BOD means water is very polluted, so cleaning water aims to reduce its BOD.

🎯 Exam Tip: Define BOD precisely and explain its significance as an indicator of water pollution and the effectiveness of wastewater treatment.

 

Question 14. Explain the role of cry-genes in genetically modified crops.
Answer: Cry-genes come from a soil bacteria called Bacillus thuringiensis. This bacteria naturally produces a poison known as cry toxin, which is harmful to certain insects. Scientists have taken these cry-genes and put them into crops like cotton. This genetic engineering makes the cotton plants produce their own cry toxin, so they become resistant to insects, like bollworms. When insects eat these genetically modified cotton plants, the cry toxin in the plant becomes active in the insect's alkaline gut. The toxin then creates holes in the insect's gut lining, which paralyzes its digestive system and causes the insect to stop eating and die. This is an environmentally friendly way to protect crops from pests. The toxins are very specific and do not harm humans or other beneficial insects.
In simple words: Cry-genes from bacteria are put into crops to make them produce a natural insect poison. This helps the crops fight off pests like bollworms on their own, reducing the need for chemical sprays.

🎯 Exam Tip: Emphasize that cry-genes provide built-in pest resistance in genetically modified crops, reducing insecticide use and improving yield.

 

Question 15. Write the key features of organic farming.
Answer: The key features of organic farming include:

• Protecting soil quality by using natural materials and encouraging healthy biological activity in the soil.
• Providing nutrients to crops indirectly through the work of helpful soil microorganisms.
• Fixing nitrogen in the soil using legume plants, which naturally add nitrogen.
• Controlling weeds and pests by using methods like rotating crops, increasing biodiversity, using natural predators, applying organic fertilizers, and employing suitable physical, heat, or biological methods. Organic farming avoids synthetic pesticides and fertilizers, focusing on ecological balance.

In simple words: Organic farming focuses on keeping soil healthy with natural materials, using microbes to feed plants, and controlling pests and weeds naturally. It avoids artificial chemicals to grow food.

🎯 Exam Tip: List the main principles of organic farming, such as soil health, biological control, and nutrient cycling, to show a comprehensive understanding.

 

Question 16. Justify the role of microbes as a bio-fertilizer.
Answer: Biofertilisers are special products that contain living microorganisms. When these are put into the soil, they make the soil richer in nutrients. They also improve the soil's physical and chemical properties, like its structure, how well it holds water, and its pH. This is because they add many nutrients and organic matter. Key biofertilisers include bacteria, fungi, and cyanobacteria. For example, Rhizobium bacteria live in the roots of legume plants and help them turn nitrogen gas from the air into forms plants can use. Other bacteria, like Azospirillum and Azotobacter, live freely in the soil and also fix atmospheric nitrogen, increasing the soil's nitrogen content. Fungi also form a symbiotic partnership with plant roots, called mycorrhiza. These fungi help plants absorb phosphorus from the soil. Plants with mycorrhizal associations grow better, are stronger against root diseases, and can handle salty or dry conditions more easily. Cyanobacteria, also known as blue-green algae, are another group of prokaryotic organisms that can fix nitrogen, especially in waterlogged paddy fields. They also release substances that help plants grow. All these roles show how important microbes are for plant growth and soil health.
In simple words: Microbes act as bio-fertilisers by adding nutrients to the soil and making it healthier. They help plants get nitrogen and phosphorus, making them grow stronger and more resistant to stress.

🎯 Exam Tip: When explaining bio-fertilisers, give specific examples of microbes (e.g., Rhizobium, Azotobacter, mycorrhiza, cyanobacteria) and describe their distinct mechanisms of enhancing soil fertility and plant growth.

 

Question 17. Write short notes on the following.
(a) Brewer's yeast
(b) Ideonella sakaiensis
(c) Microbial fuel cells
Answer:
(a) Brewer's yeast: This is a type of fungus called Saccharomyces cerevisiae. It is widely used to make bakery items like dough soft and fluffy, and also for preparing various fermented alcoholic beverages. It helps dough rise by producing carbon dioxide.
(b) Ideonella sakaiensis: This is a special type of bacterium that helps recycle PET plastics. It makes enzymes called PETase and MHETase, which break down PET plastics into simpler chemicals like terephthalic acid and ethylene glycol. This makes it a potential solution for plastic pollution.
(c) Microbial fuel cells: A microbial fuel cell is like a battery that uses bacteria to make electricity. It is a bio-electrochemical system that uses bacteria to oxidize and reduce organic molecules, creating an electric current. Inside the cell, microbes at one end (anode) break down organic fuel, producing protons and electrons. The protons pass through a special membrane, while the electrons travel through an external circuit to the other end (cathode), generating power. This technology has the potential to convert waste into electricity.

In simple words: Brewer's yeast makes bread soft and alcohol. Ideonella sakaiensis bacteria can break down plastic. Microbial fuel cells use bacteria to make electricity from organic matter.

🎯 Exam Tip: For short notes, provide a clear definition and one or two key applications or functions for each term, using precise scientific language.

 

Question 18. List the advantages of biogas plants in rural areas.
Answer: Biogas plants offer several advantages in rural areas. Biogas is a valuable fuel that can be used for both cooking and lighting, providing clean energy for households. The technology for producing biogas was developed in India through the dedicated efforts of organizations like the Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC). Besides energy, the leftover slurry from biogas production is an excellent organic fertilizer, enriching soil and boosting crop yields. This makes biogas plants a sustainable solution for waste management and rural development.
In simple words: Biogas plants in villages provide clean gas for cooking and light. They also create good fertilizer for farms, making them useful for energy and agriculture.

🎯 Exam Tip: When listing advantages, consider multiple aspects like energy, waste management, and agricultural benefits to show a holistic understanding of the technology.

 

Question 19. When does antibiotic resistance develop?
Answer: Antibiotic resistance happens when bacteria learn to fight off the drugs that are supposed to kill them or stop their growth. This is a very serious danger to public health. The problem gets worse when antibiotics are misused or overused, and when people do not follow good hygiene to prevent infections. Antibiotics should only be taken when a doctor prescribes them. When bacteria become resistant, antibiotics no longer work, and the bacteria keep multiplying, making infections harder to treat. Using narrow-spectrum antibiotics, which target specific germs, is better than broad-spectrum ones, as it reduces the chances of resistance. This careful approach helps preserve the effectiveness of existing antibiotics.
In simple words: Antibiotic resistance develops when bacteria change and can no longer be killed by medicines. This often happens because antibiotics are used too much or incorrectly.

🎯 Exam Tip: Emphasize that antibiotic resistance is an evolutionary process driven by misuse, highlighting the importance of proper antibiotic stewardship and infection control.

 

Question 20. What is the key difference between primary and secondary sewage treatment?
Answer: The key differences between primary and secondary sewage treatment are as follows:
Primary Treatment:
1. This stage physically removes large particles and floating debris from the wastewater.
2. Solid materials, along with organic and inorganic particles, are taken out.
3. The main methods used are screening, sedimentation (where heavier particles settle down), and filtration. This stage mainly aims to remove suspended solids.
Secondary Treatment:
1. This stage uses biological methods, primarily microorganisms, to further clean the water.
2. Organic matter that is dissolved or finely suspended is removed by microbes.
3. The key processes involve aeration (adding air) and aerobic microbial degradation, where bacteria break down organic pollutants. This significantly reduces the Biological Oxygen Demand (BOD) of the water.
In simple words: Primary sewage treatment removes big and heavy solid waste by physical filtering and settling. Secondary treatment then uses bacteria to break down the smaller, dissolved organic waste.

🎯 Exam Tip: Clearly differentiate between the physical removal in primary treatment and the biological degradation in secondary treatment, noting the role of microbes in the latter.

 

Additional Important Questions and Answers

 

Question 1. The leavening of the dough during fermentation is due to
(a) Formation of ethyl alcohol
(b) Formation of CO2
(c) Formation of oxygen
(d) Action of zymase enzyme
Answer: (b) Formation of CO2
In simple words: Dough rises because yeast produces carbon dioxide gas during fermentation. This gas gets trapped in the dough, making it expand and become light.

🎯 Exam Tip: Remember that carbon dioxide gas is the primary cause of dough leavening, not alcohol, even though both are products of yeast fermentation.

 

Question 2. Match list I with list II
Answer:

The correct match is a-iv, b-iii, c-ii, d-i. Each raw material is fermented by microbes to produce a specific alcoholic beverage. For example, barley is used for beer, sugarcane for rum, palm sap for toddy, and grape juice for wine.
In simple words: Different starting ingredients are used to make different types of alcohol. For example, grapes make wine, and sugarcane makes rum.

🎯 Exam Tip: Memorize the common raw materials and the alcoholic beverages produced from them through microbial fermentation.

 

Question 3. Name the person who was the first to use the term antibiotic.
(a) Selman Waksman
(b) Alexander Flemming
(c) Earnest Chain
(d) Howard Florey
Answer: (a) Selman Waksman
In simple words: Selman Waksman was the scientist who first used the word "antibiotic" to describe substances that kill harmful microbes. He also discovered streptomycin.

🎯 Exam Tip: Distinguish between the discoverer of penicillin (Fleming) and the person who coined the term "antibiotic" (Waksman), as this is a common point of confusion.

 

Question 4. ........... is commonly referred as the Queen of drugs.
Answer: Penicillin is commonly referred as the Queen of drugs. Penicillin was the first true antibiotic discovered, and it revolutionized medicine by saving countless lives from bacterial infections. Its broad impact on public health earned it this esteemed title.
In simple words: Penicillin is called the "Queen of drugs" because it was the first antibiotic and changed how we treat infections forever.

🎯 Exam Tip: Recognize important historical facts and common nicknames in biology, such as "Queen of drugs" for penicillin, which highlight their significance.

 

Question 5. Tetracycline is a ...........
(i) bactericidal antibiotic
(ii) bacteriastatic antibiotic
(iii) narrow spectrum antibiotic
(iv) Broad spectrum antibiotic
(a) i and iii
(b) ii and iii
(c) i and iv
(d) ii and iv
Answer: (d) ii and iv
In simple words: Tetracycline is an antibiotic that stops bacteria from growing, rather than killing them (bacteriostatic). It also works against a wide range of different bacteria, meaning it is a broad-spectrum antibiotic.

🎯 Exam Tip: Understand the difference between bacteriostatic (stops growth) and bactericidal (kills bacteria) antibiotics, as well as narrow-spectrum (specific targets) and broad-spectrum (wide range) antibiotics.

 

Question 6. Chlortetracycline was isolated from the culture ...........
(a) Streptomyces aureofaciens
(b) Streptomyces griseus
(c) Streptococcus lactis
(d) Aspergillus niger
Answer: (a) Streptomyces aureofaciens
In simple words: Chlortetracycline, an important antibiotic, was first found and taken from a special type of bacteria called Streptomyces aureofaciens. This shows how microbes can be a source of useful medicines.

🎯 Exam Tip: Connect specific antibiotics with the microbial species from which they were originally isolated, as this highlights the role of microbes in drug discovery.

 

Question 7. Identify the name and the formula of industrial alcohol.
(a) Butanol, C4H9OH
(b) Propanol, C3H7OH
(c) Ethanol, C2H5OH
(d) Methanol, CH3OH
Answer: (c) Ethanol, C2H5OH
In simple words: Ethanol, which has the chemical formula \( C_2H_5OH \), is commonly known as industrial alcohol. It is widely used in various industries for many purposes.

🎯 Exam Tip: Know the common name and chemical formula for ethanol, especially its significance as an industrial alcohol and biofuel.

 

Question 8. Pick the bacterial species which is not used in ethanol formation.
(a) Zymomonas mobilis
(b) Sarcina ventriculi
(c) Saccharomyces cerevisiae
(d) Streptomyces aureofaciens
Answer: (d) Streptomyces aureofaciens
In simple words: Streptomyces aureofaciens is a bacterium that makes antibiotics, not ethanol. Other microbes like Zymomonas mobilis, Sarcina ventriculi, and Saccharomyces cerevisiae (yeast) are known for their ability to produce ethanol.

🎯 Exam Tip: Be able to identify which microorganisms are involved in specific industrial processes like ethanol production and which are not.

 

Question 9. Match the Microbes with the respective organic acids
Answer:

The correct match is a-ii, b-i, c-iv, d-iii. This table pairs common microbes with the specific organic acids they produce. For instance, Aspergillus makes citric acid, Acetobacter makes acetic acid, Rhizopus makes fumaric acid, and Clostridium makes butyric acid.
In simple words: Different types of microbes create different natural acids. For example, a microbe called Aspergillus makes citric acid, while Acetobacter makes acetic acid.

🎯 Exam Tip: Familiarize yourself with the industrial production of organic acids and the specific microorganisms responsible for each acid, as this is frequently tested.

 

Question 10. Human insulin is being commercially produced from a transgenic species of...........
(a) Escherichia
(b) Mycobacterium
(c) Streptococcus
(d) Penicillin
Answer: (a) Escherichia
In simple words: Human insulin, which is used to treat diabetes, is made in large amounts by genetically modified Escherichia coli (E. coli) bacteria. Scientists put the human insulin gene into E. coli to make it produce this important medicine.

🎯 Exam Tip: Remember Escherichia coli as the primary transgenic organism used for the commercial production of human insulin, showcasing biotechnology's impact.

 

Question 11. Select the correct statement from the following.
(a) Primary treatment of sewage involves biological oxidation
(b) Excreta of cattle is commonly called Gobur
(c) Delta endotoxin of Bacillus thuringiensis is encoded by pen-genes.
(d) Trichoderma is a free-timing bacteria very common in root ecosystem.
Answer: (b) Excreta of cattle is commonly called Gobur
In simple words: The correct statement is that cattle waste is often called Gobur. Primary sewage treatment is about physical removal, not biological oxidation. Delta endotoxin genes are 'cry' genes, not 'pen' genes. Trichoderma is a fungus, not a bacterium.

🎯 Exam Tip: Carefully evaluate each option based on your knowledge of sewage treatment, biotechnology, and microbiology to identify the single correct statement.

 

Question 12. Oil strains in laundry can be removed using ....................
(a) Peptidane
(b) Protease
(c) Amylase
(d) Lipase
Answer: (d) Lipase
In simple words: Lipase is an enzyme that helps clean oily stains from clothes.

🎯 Exam Tip: Remember that different enzymes break down different substances – proteases break down proteins, amylases break down starches, and lipases break down fats.

 

Question 13. Find the odd sentence out.
(i) Biogas primarily consists of methane with CO2 and hydrogen
(ii) The greater the BOD of wastewater the more its polluting potential
(iii) World biofuel day is observed on 10th August
(iv) Cyclosporin A is obtained from Trichoderma polysporum.
(a) i and iii
(b) ii and iv
(c) i and iv
(d) None of the options
Answer: (d) None of the options
In simple words: All the sentences given are true. So, there is no odd one out among them.

🎯 Exam Tip: When asked to find the 'odd one out', carefully evaluate the factual accuracy of each statement to determine which, if any, is incorrect.

 

Question 14. Match with correct pair
(a) Biofertilizer (i) Bacillus thuringiensis
(b) Bioremediation (ii) Rhizobium
(c) Biopesticide (iii) Pseudomonas
(d) Bioherbicide (iv) Phytophthora palmivora
Answer: a – ii, b – iii, c-i, d-iv
In simple words: We need to match each item with its correct partner. Biofertilizers use Rhizobium, bioremediation uses Pseudomonas, biopesticides use Bacillus thuringiensis, and bioherbicides use Phytophthora palmivora.

🎯 Exam Tip: Familiarize yourself with examples of microorganisms and their specific applications in different biotechnological fields to score well on matching questions.

 

12th Bio Zoology Guide Microbes in Human Welfare Additional Important Questions and Answers

 

Question 15. Name the genus of virus which are used as effective Biocontrol agent.
Answer: Nucleopolyhedrovirus is a type of virus that acts as an effective biocontrol agent. These viruses are often used to control insect pests in an environmentally friendly way.
In simple words: Viruses called Nucleopolyhedrovirus are good at controlling pests naturally.

🎯 Exam Tip: When naming specific biological agents, ensure correct spelling and capitalization (genus capitalized, species lowercase) for accuracy.

 

Question 16. Statement 1: Prebiotics are the compounds in food that induce the growth of beneficial microbes
Statement 2: LAB is a probiotic
(a) Statement 1 is correct. Statement 2 is incorrect.
(b) Statement 1 is incorrect. Statement 2 is correct.
(c) Both statements 1 and 2 are incorrect.
(d) Both statements 1 and 2 are correct.
Answer: (d) Both statements 1 and 2 are correct.
In simple words: The first statement says prebiotics help good microbes grow, which is true. The second statement says LAB is a probiotic, which is also true.

🎯 Exam Tip: Understand the difference between prebiotics (food for microbes) and probiotics (the microbes themselves) for clarity in such questions.

 

Question 17. Statement 1: Saccharomyces cerevisiae is commonly called as Baker's yeast.
Statement 2: Yogurt is produced by the fermentation of milk by saccharomyces cerevisiae
(a) Statement 1 is correct. Statement 2 is incorrect.
(b) Statement 1 is incorrect. Statement 2 is correct.
(c) Both statements 1 and 2 are incorrect.
(d) Both statements 1 and 2 are correct.
Answer: (a) Statement 1 is correct. Statement 2 is incorrect.
In simple words: Baker's yeast is Saccharomyces cerevisiae, so statement 1 is right. But yogurt is made by bacteria, not this yeast, so statement 2 is wrong.

🎯 Exam Tip: Be precise about which microorganisms are responsible for specific fermentation products; bacteria make yogurt, while yeast makes bread and alcohol.

 

Question 18. The flavour in the yogurt is due to ....................
(a) Formaldehyde
(b) Lactate
(c) Acetaldehyde
(d) Caesin
Answer: (c) Acetaldehyde
In simple words: The special taste of yogurt is caused by acetaldehyde, made when milk ferments.

🎯 Exam Tip: Remember key compounds responsible for distinct flavors in fermented foods, as these are often tested.

 

Question 19. Assertion (A): Streptomycin is an antibiotic.
Reason (R): Antibiotic are microbial chemicals inhibits the growth of pathogenic microbe.
(a) A is right R is wrong.
(b) R explains A.
(c) A and R are wrong.
(d) A and R are right. R cannot explain A.
Answer: (b) R explains A.
In simple words: Streptomycin is an antibiotic (A is true). Antibiotics stop bad microbes from growing (R is true). R explains A because that's how streptomycin works.

🎯 Exam Tip: In assertion-reason questions, first check if both statements are true, then determine if the reason directly explains the assertion.

 

Question 20. Assertion (A): Oenology deals with study of wine and its preparation.
Reason (R): Zymology deals with the biochemical process of fermentation and its uses.
(a) A is right R is wrong.
(b) R explains A.
(c) A and R are wrong.
(d) A and R are right. R cannot explain A.
Answer: (d) A and R are right. R cannot explain A.
In simple words: Both statements are true. Oenology is about wine, and Zymology is about fermentation. But Zymology doesn't explain Oenology; they are different topics.

🎯 Exam Tip: Be careful not to confuse related but distinct fields of study; ensure the reason logically connects to and explains the assertion.

 

Question 21. In primary sewage treatment, the floating debris are removed by....................
(a) Distillation
(b) Sedimentation
(c) Sequential filtration
(d) Biological oxidation
Answer: (c) Sequential filtration
In simple words: Floating trash in sewage is taken out by filtering it many times, which is called sequential filtration.

🎯 Exam Tip: Understand the order and purpose of each step in sewage treatment, starting with physical removal of large impurities.

 

Question 22. Yamuna Action Plan was a bilateral project signed between
(a) India and Pakistan Government
(b) India and Japan Government
(c) India and China Government
(d) India and Srilanka Government
Answer: (b) India and Japan Government
In simple words: The Yamuna Action Plan was a project where India and Japan worked together.

🎯 Exam Tip: For environmental initiatives, be aware of the involved countries or organizations.

 

Question 23. Select the correct option denoting the proper sequence of sewage tratment.
(a) Filtration, Sedimentation, Aeration, Biological oxidation and UV radiation
(b) Sedimentation, Filtration, Biological oxidation, Aeration and UV radiation.
(c) Filtration, Aeration, Biological oxidation, Sedimentation and UV radiation.
(d) UV radiation, Sedimentation, Filtration, Biological oxidation and Aeration.
Answer: (a) Filtration, Sedimentation, Aeration, Biological oxidation and UV radiation
In simple words: Sewage treatment starts with filtering, then letting solids sink, then using air and microbes to clean, and finally UV light to kill germs.

🎯 Exam Tip: Memorize the correct sequential steps of wastewater treatment, from primary physical methods to secondary biological and tertiary disinfection.

 

Question 24. The Ganga action plan was launched on .....................
Answer: The Ganga Action Plan was officially launched on January 14, 1986. This plan was a major government effort to reduce pollution in the Ganga River.
In simple words: The Ganga Action Plan began on January 14, 1986, to clean up the Ganga River.

🎯 Exam Tip: Key dates for important national projects are often asked in exams; remember both the day, month, and year.

 

Question 25. Which of the following plant species is the most suitable oilseed for biodirect production?
(a) Ground nut
(b) Areca nut
(c) Jatropha curcas
(d) Phyllanthus anarus
Answer: (c) Jatropha curcas
In simple words: Jatropha curcas is the best plant to grow for making biodiesel fuel.

🎯 Exam Tip: Focus on specific examples of plants or organisms mentioned in relation to biotechnological applications like biofuel production.

 

Question 26. Match the following medicinal products with their microbial source.
(a) Humulin (z) Streptococcus
(b) Statins (ii) Trichoderma polysporum
(c) Cyclosporin A (z'z'z) Monascus purpureus
(d) Streptokinase (z'v) E-coli
Answer: a – iv, b – iii, c – ii, d-i
In simple words: Humulin comes from E-coli, Statins from Monascus purpureus, Cyclosporin A from Trichoderma polysporum, and Streptokinase from Streptococcus.

🎯 Exam Tip: Create flashcards for important microbial products and their specific microbial sources to master these matching questions.

 

12th Bio Zoology Guide Microbes in Human Welfare Two Marks Questions and Answers

 

Question 1. What does LAB stands for? Give two examples.
Answer: LAB stands for Lactic Acid Bacteria. Two examples are Lactobacillus lactis and Streptococcus lactis. These bacteria are important in making fermented foods.
In simple words: LAB means Lactic Acid Bacteria. Lactobacillus lactis and Streptococcus lactis are two kinds of them.

🎯 Exam Tip: When defining acronyms, always provide the full form and a relevant example to show complete understanding.

 

Question 2. Define LAB.
Answer: Lactic Acid Bacteria (LAB) are a group of beneficial microbes, also known as probiotics. They help keep the stomach and other digestive system parts healthy by preventing harmful microbes from growing. They are essential for gut health.
In simple words: LAB are good bacteria called probiotics. They stop bad germs from growing in our stomach and gut.

🎯 Exam Tip: Emphasize the 'probiotic' nature and the function of inhibiting pathogenic microbes when defining LAB.

 

Question 3. Given below are the food products obtained by microbial action. Name the respective organism responsible for their production, (a) Swiss Cheese (6) Bread dough
Answer:
(a) Swiss Cheese is produced by Propionibacterium shermanii. This bacterium helps create the distinct flavor and holes in the cheese.
(b) Bread dough rises because of Saccharomyces cerevisiae, also known as baker's yeast, which ferments the sugars.
In simple words: Propionibacterium shermanii makes Swiss cheese, and Saccharomyces cerevisiae (yeast) makes bread dough rise.

🎯 Exam Tip: Be sure to name both the food product and the specific microorganism responsible, along with its function.

 

Question 4. What is SCP?
Answer: SCP stands for Single Cell Protein. It refers to edible protein that comes from single-celled organisms such as algae (like Spirulina), yeasts, fungi, or bacteria. These proteins can be used as food ingredients or as a high-protein food source for both humans and animals. This is a way to produce protein sustainably.
In simple words: SCP means Single Cell Protein, which is protein from tiny organisms like algae or yeast. We can eat it, and it's also used for animal food.

🎯 Exam Tip: For definitions, provide the full form of the acronym, explain what it is, and give examples of its sources and uses.

 

Question 5. What is fermentor?
Answer: A fermentor, also known as a bioreactor, is a sealed container designed for controlled growth of microorganisms. It has systems to control air flow (aeration), mixing (agitation), temperature, and pH, along with an outlet to remove waste and desired products. It's like a special tank where microbes can grow and make useful things.
In simple words: A fermentor is a closed tank where microbes grow to make products. It has controls for air, mixing, heat, and acidity.

🎯 Exam Tip: When describing equipment like a fermentor, detail its key features and functions rather than just a simple definition.

 

Question 6. What are antibiotics?
Answer: Antibiotics are special chemical substances made by some microorganisms. They can either kill or slow down the growth of other harmful, disease-causing microbes, even when used in small amounts. The word "antibiotic" actually means "against life" (referring to harmful microbial life).
In simple words: Antibiotics are chemicals from microbes that kill or stop the growth of bad germs. They work even in small doses.

🎯 Exam Tip: Include both the source (microorganisms) and the mechanism of action (killing or retarding growth) in your definition of antibiotics.

 

Question 7. Give reason, (a) Flavour in Yogurt (6) Large holes in Swiss Cheese
Answer:
(a) The flavor in yogurt comes from the formation of acetaldehyde during the fermentation process.
(b) The large holes in Swiss cheese are created by the gas carbon dioxide (CO2), which is produced in large amounts by the bacterium Propionibacterium shermanii as it grows.
In simple words: Yogurt tastes unique because of acetaldehyde. Swiss cheese has big holes because a bacteria called Propionibacterium shermanii makes a lot of CO2 gas.

🎯 Exam Tip: Provide specific chemical compounds (acetaldehyde) or microorganisms (*Propionibacterium shermanii*) and their products (CO2) when explaining reasons for biological phenomena.

 

Question 8. Name few industrial microbial products.
Answer: Microbes are used to produce many industrial products, including various beverages, antibiotics, organic acids, amino acids, vitamins, and biofuels. They also help in making single-cell protein, enzymes, steroids, vaccines, and other pharmaceutical drugs.
In simple words: Microbes help make drinks, medicines, acids, vitamins, fuels, proteins, enzymes, and vaccines for industries.

🎯 Exam Tip: List a diverse range of products to demonstrate the broad impact of industrial microbiology.

 

Question 9. Name few home-made micorbial products.
Answer: Some common homemade products made using microbes include yogurt, paneer (a type of cheese), curd, idli batter (for South Indian steamed cakes), and bread dough. These all rely on microbial fermentation.
In simple words: Yogurt, paneer, curd, idli batter, and bread dough are some foods we make at home using microbes.

🎯 Exam Tip: Distinguish between industrial and homemade microbial products; homemade ones often involve simpler, traditional fermentation processes.

 

Question 10. Who derived the term antibiotic? Name the antibiotic which he discovered.
Answer: The term "antibiotic" was first used by Selman Waksman in 1943. He is also credited with discovering the antibiotic Streptomycin. His work was very important for medicine.
In simple words: Selman Waksman first used the word "antibiotic" in 1943. He found the antibiotic called Streptomycin.

🎯 Exam Tip: Always include the name of the scientist, the term, and the associated discovery when answering historical questions.

 

Question 11. The first antibiotic was extracted from fungus. Who had done it? And also mention the fungal species used.
Answer: The first antibiotic, penicillin, was discovered by Alexander Fleming. He extracted it from the fungus Penicillium notatum. Later, Penicillium chrysogenum was also found to be a good source for penicillin production. This discovery changed medicine forever.
In simple words: Alexander Fleming found the first antibiotic, penicillin, from a fungus called Penicillium notatum (and Penicillium chrysogenum).

🎯 Exam Tip: Know the full story of penicillin's discovery: the scientist, the name of the antibiotic, and the microbial source.

 

Question 12. Write as example for (a) Bacteriostatic antibiotic (b) Bactericidal antibiotic
Answer:
(a) A bacteriostatic antibiotic is one that stops bacteria from growing but does not necessarily kill them; an example is Tetracycline.
(b) A bactericidal antibiotic is one that actively kills bacteria; an example is Streptomycin.
In simple words: Tetracycline is a bacteriostatic antibiotic (it stops bacteria from growing). Streptomycin is a bactericidal antibiotic (it kills bacteria).

🎯 Exam Tip: Clearly differentiate between 'static' (stopping growth) and 'cidal' (killing) effects of antibiotics and provide clear examples for each.

 

Question 13. Name any four antibiotics.
Answer: Four common antibiotics are Erythromycin, Chloromycetin, Neomycin, and Kanamycin. Each of these medicines helps fight different types of bacterial infections.
In simple words: Four antibiotics are Erythromycin, Chloromycetin, Neomycin, and Kanamycin.

🎯 Exam Tip: Keep a mental list of common antibiotics and their classifications.

 

Question 14. Compare Broad-spectrum antibiotics with narrow-spectrum antibiotics.
Answer: Broad-spectrum antibiotics are medicines that work against many different kinds of bacteria that cause diseases. On the other hand, narrow-spectrum antibiotics are specific, targeting only a small, particular group of bacteria. Doctors choose which type to use based on the infection.
In simple words: Broad-spectrum antibiotics fight many types of bacteria, while narrow-spectrum ones fight only a few specific types.

🎯 Exam Tip: Focus on the 'range' of activity when comparing these two types of antibiotics, as that is their defining difference.

 

Question 15. Define (a) Antibiosis (A) Superbugs
Answer:
(a) Antibiosis is the property where one organism produces substances that harm or kill other organisms, like how antibiotics kill microbes.
(b) Superbugs are types of bacteria that have developed resistance to many common antibiotics, making them very hard to treat.
In simple words: Antibiosis is when one living thing hurts another, like antibiotics killing germs. Superbugs are bacteria that strong medicines can no longer kill.

🎯 Exam Tip: Clearly define each term, highlighting the key characteristic - for antibiosis, the inhibitory effect, and for superbugs, antibiotic resistance.

 

Question 16. What is studied under zymology and oenology?
Answer: Zymology is the study of fermentation, which is a biochemical process, and how it is used. Oenology, on the other hand, focuses on the study of wine and all aspects of winemaking. Both fields involve the action of microorganisms.
In simple words: Zymology studies how things ferment and their uses. Oenology studies wine and how it is made.

🎯 Exam Tip: Use clear, concise definitions for each term, emphasizing their distinct subjects of study.

 

Question 17. Saccharomyces cerevisiae is called as brewer's yeast. Justify.
Answer: Saccharomyces cerevisiae is called brewer's yeast because it is widely used to ferment malted grains (like barley) and fruit juices. This fermentation process produces various alcoholic drinks. For example, it is essential for making beer and wine. Distilled spirits like whisky and rum also start with fermentation by this yeast, followed by distillation.
In simple words: It's called brewer's yeast because it ferments cereals and fruit juices to make alcohol in drinks like beer and wine.

🎯 Exam Tip: When asked to justify, explain the reason or evidence behind the statement, often linking it to practical applications.

 

Question 18. How wine is made? Which organism is involved in the process.
Answer: Wine is made through the fermentation of grape juice. Various strains of Saccharomyces cerevisiae, commonly known as yeast, convert the sugars in the grape juice into alcohol. This is a natural process where the yeast consumes sugar and produces ethanol.
In simple words: Wine is made when yeast, mainly Saccharomyces cerevisiae, ferments grape juice, turning its sugar into alcohol.

🎯 Exam Tip: Specify both the raw material (grape juice) and the key microorganism (*Saccharomyces cerevisiae*) in your explanation of wine production.

 

Question 19. Name the 2 types of grape wine. How they differ from one another?
Answer: There are two main types of grape wine: red wine and white wine. Red wine is made using black grapes, and the grape skins (and sometimes stems) are included in the fermentation, giving it color and tannins. White wine, however, is made only from the juice of either white or red grapes, with the skins and stems removed before fermentation, resulting in a lighter color.
In simple words: The two types are red wine and white wine. Red wine uses black grapes with skins, while white wine uses only the juice of white or red grapes, without the skins.

🎯 Exam Tip: Highlight the role of grape skins in distinguishing red from white wine production.

 

Question 20. Saccharomyces Cerevisiae is a widely used fungus in making beverages. Considering this complete the table by mentioning the raw material and respective product.
Answer: Saccharomyces cerevisiae (brewer's yeast) is used to ferment various raw materials into different alcoholic beverages. Here is the completed table showing the raw material and its corresponding product:

This yeast plays a vital role in brewing and distilling worldwide.
In simple words: The table shows how Saccharomyces cerevisiae yeast changes different ingredients like grape juice, barley, grain mash, and sugarcane into drinks like wine, beer, whisky, and rum.

🎯 Exam Tip: When completing tables, ensure all columns are filled accurately according to the prompt, and present the information clearly.

 

Question 21. Ethanol is a industrial alcohol – Justify.
Answer: Ethanol (\( \text{C}_2\text{H}_5\text{OH} \)) is considered an industrial alcohol because it is largely produced by microorganisms like Saccharomyces cerevisiae and has widespread use in various industries. It serves as a solvent in laboratories, a raw material in chemical manufacturing, and as a fuel additive, making it a critical industrial compound.
In simple words: Ethanol is called industrial alcohol because it's made a lot by yeast and used in many factories, labs, and even in fuel.

🎯 Exam Tip: Justifications require providing specific reasons and applications that support the given statement, such as ethanol's diverse uses.

 

Question 22. Name the bacterial species involved in ethanol production.
Answer: The bacterial species primarily involved in ethanol production are Zymomonas mobilis and Sarcina ventriculi. These bacteria are efficient in converting sugars into ethanol, similar to yeast.
In simple words: The bacteria Zymomonas mobilis and Sarcina ventriculi help make ethanol.

🎯 Exam Tip: While yeast is common, remember that certain bacterial species are also capable of ethanol fermentation.

 

Question 23. What are the substrates used in producing industrial alcohol.
Answer: The main raw materials, or substrates, used for producing industrial alcohol include molasses, corn, potatoes, and wood wastes. These materials are rich in fermentable sugars or starches that microbes can convert into alcohol.
In simple words: Industrial alcohol is made from things like molasses, corn, potatoes, and wood waste.

🎯 Exam Tip: List raw materials that are abundant and contain high amounts of carbohydrates for efficient fermentation.

 

Question 24. Write the equation for alcoholic fermentation.
Answer: The chemical equation for alcoholic fermentation, a process carried out by yeast, is:
\[ \text{C}_6\text{H}_{12}\text{O}_6 \xrightarrow{\text{Yeast / Fermentation}} 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2 \uparrow \]
In this reaction, glucose (a sugar) is converted into ethanol (alcohol) and carbon dioxide gas. This process is key for making alcoholic beverages and biofuels.
In simple words: Glucose sugar changes into ethanol (alcohol) and carbon dioxide gas with the help of yeast.

🎯 Exam Tip: Ensure chemical formulas are correct, the arrow indicates the reaction direction, and the catalyst/conditions (Yeast/Fermentation) are specified above the arrow.

 

Question 25. Complete the table by filling with respective organic acid and microbes.
Answer: Microbes play a crucial role in producing various organic acids through fermentation. Here is the completed table showing the specific organic acid and the microbe responsible for its production:

This demonstrates the diverse applications of microbial biotechnology.
In simple words: The table shows which microbes make which organic acids. For example, Acetobacter aceti makes acetic acid, and Aspergillus niger makes citric acid.

🎯 Exam Tip: Pay close attention to the specific pairing of each organic acid with its corresponding microbial producer.

 

Question 26. Genetically engineered Streptococci is used in medicine. How?
Answer: Genetically engineered Streptococci bacteria are used in medicine as "clot busters." They produce an enzyme called streptokinase, which helps dissolve blood clots that form in blood vessels, especially in patients who have had a heart attack (myocardial infarction). This can save lives by restoring blood flow.
In simple words: Special Streptococci bacteria are changed to make a "clot buster" medicine. This medicine helps break up dangerous blood clots in people who have had a heart attack.

🎯 Exam Tip: Mention both the specific engineered organism (*Streptococci*) and the name of the enzyme it produces (streptokinase) for a complete answer.

 

Question 27. Write a brief note on Cyclosporin A.
Answer: Cyclosporin A is a powerful drug that lowers the body's immune response, making it an immunosuppressant. It is produced from the fungus Trichoderma polysporum. This drug is mainly used in organ transplant surgeries to prevent the patient's body from rejecting the new organ. It also has properties that can help fight inflammation, fungi, and parasites.
In simple words: Cyclosporin A is a medicine from the fungus Trichoderma polysporum. It stops the body from fighting against new organs in transplant operations. It also helps with swelling and fights fungi and parasites.

🎯 Exam Tip: Clearly state Cyclosporin A's primary function (immunosuppressant), its microbial source, and its main medical application (organ transplantation).

 

Question 28. State the source of statins and its medical role.
Answer: Statins are a type of drug obtained from the red yeast fungus Monascus purpureus. Their medical role is to reduce high blood cholesterol levels. They do this by blocking an enzyme in the body that is responsible for making cholesterol, which helps prevent heart disease.
In simple words: Statins come from a yeast fungus called Monascus purpureus. They work by stopping the body from making too much bad cholesterol, which keeps our hearts healthier.

🎯 Exam Tip: When asked for source and role, name the specific organism and explain the mechanism of action for the medical benefit.

 

Question 29. Expand and define BOD.
Answer: BOD stands for Biochemical Oxygen Demand (or Biological Oxygen Demand). It measures how much oxygen would be used up by bacteria to break down all the organic waste in one liter of water. A higher BOD means there is more pollution in the water. Monitoring BOD helps assess water quality.
In simple words: BOD means Biochemical Oxygen Demand. It tells us how much oxygen bacteria would use to break down all the waste in water. More BOD means more dirty water.

🎯 Exam Tip: Always provide the full form of the acronym and clearly state what it measures and what its implications are (e.g., higher BOD means more pollution).

 

Question 30. Define activated sludge.
Answer: Activated sludge is the solid material, rich in bacterial 'flocs' (masses of bacteria), that settles at the bottom of a settling tank after the biological treatment of sewage. This sludge is very important because it contains active microbes that can be reused to treat more wastewater, speeding up the purification process.
In simple words: Activated sludge is the settled part of sewage treatment that is full of good bacteria. This bacteria-rich mud helps clean more dirty water.

🎯 Exam Tip: Highlight the composition (bacterial flocs) and the function (reused as inoculum) when defining activated sludge.

 

Question 31. Give a brief account on Ganga action plan.
Answer: The Ganga Action Plan was launched on January 14, 1986. Its main goal was to improve the water quality of the River Ganges. This was done by stopping sewage from directly entering the river, diverting it for treatment, and identifying big polluters to prevent them from releasing waste. It was a large-scale effort to restore the river.
In simple words: The Ganga Action Plan, started in 1986, aimed to clean the River Ganges. It did this by treating dirty water and stopping big polluters.

🎯 Exam Tip: Include the launch date, primary objective, and key strategies employed by the plan.

 

Question 32. Name the biocontrol agents used to get rid of Aphids & mosquito larvae.
Answer: Ladybird beetles are used as biocontrol agents to get rid of aphids, while dragonflies are effective against mosquito larvae. These are natural ways to control pests without using chemicals.
In simple words: Ladybird beetles help remove aphids, and dragonflies help remove mosquito larvae.

🎯 Exam Tip: Provide specific biocontrol agents for each pest mentioned, demonstrating knowledge of natural pest control.

 

Question 33. How insect resistant plants are developed using Bacillus thuringiensis?
Answer: Insect-resistant plants are developed using Bacillus thuringiensis (Bt), a bacterium found in soil. This bacterium naturally produces a toxin called cry toxin, which is harmful to certain insects. Scientists take the gene that makes this cry toxin from Bt bacteria and insert it into plant cells, such as those of cotton. These genetically engineered plants then produce the toxin themselves, making them resistant to insect pests without needing chemical sprays. This helps reduce pesticide use.
In simple words: Scientists take a special gene from Bacillus thuringiensis bacteria that makes a toxin. They put this gene into plants like cotton, so the plants make their own insect-killing toxin and become insect-resistant.

🎯 Exam Tip: Explain the genetic engineering process: identifying the toxin gene, transferring it to the plant, and the resulting benefit (plant producing its own pesticide).

 

Question 34. Which group of insects can be controlled by using delta-endotoxins of Bt-crops?
Answer: The delta-endotoxins produced by Bt-crops are effective against several groups of insects, including Lepidoptera (like butterflies and moths), Diptera (like flies and mosquitoes), Coleoptera (like beetles), and Hymenoptera (like ants, bees, and wasps). These toxins specifically target and harm these pest insects.
In simple words: Delta-endotoxins from Bt-crops can control insects like moths, flies, beetles, and wasps.

🎯 Exam Tip: Name the specific insect orders that are targeted by Bt-toxins to provide a comprehensive answer.

 

Question 35. Name the two viruses that acts as biocontrol agents.
Answer: Two types of viruses that serve as biocontrol agents are Baculoviruses and Nucleopolyhedroviruses. These viruses are natural enemies of certain insect pests and are used to control their populations in an environmentally friendly way.
In simple words: Baculoviruses and Nucleopolyhedroviruses are two viruses used to control pests naturally.

🎯 Exam Tip: Focus on the specific names of the viruses known for their biocontrol properties.

 

Question 36. Rhizobium is a bacteria but acts as bio-fertilization. How?
Answer: Rhizobium is a special type of bacteria that helps plants. It forms a close, helpful relationship (symbiotic association) with the roots of legume plants, like beans and peas. This bacteria then takes nitrogen gas from the air and changes it into a form that plants can use. This process is like natural fertilizing, which helps these plants grow strong without needing extra chemical fertilizers.
In simple words: Rhizobium bacteria work with legume plants to turn air nitrogen into food for them, acting like a natural fertilizer.

🎯 Exam Tip: Remember that "symbiotic" means both organisms benefit from the relationship, which is key for Rhizobium and legumes.

 

Question 37. Give any two examples for free-living nitrogen-fixing bacteria.
Answer: Two examples of free-living nitrogen-fixing bacteria are Azospirillum and Azotobacter. These bacteria live independently in the soil and can take nitrogen directly from the air and convert it into a usable form for plants, unlike symbiotic bacteria that need to live inside plant roots. They play a big role in keeping soil fertile.
In simple words: Azospirillum and Azotobacter are two types of bacteria that live freely in the soil and help plants by changing nitrogen from the air into plant food.

🎯 Exam Tip: Distinguish between free-living (independent) and symbiotic (living with a host) nitrogen-fixing bacteria in your examples.

 

Question 38. Name a few blue-green algae (BGA).
Answer: A few examples of blue-green algae (BGA), also known as Cyanobacteria, include Oscillatoria, Nostoc, Anabaena, and Tolypothrix. These organisms are like tiny plant-bacteria hybrids that can make their own food through photosynthesis and also help fix nitrogen from the air, making them very useful in places like paddy fields.
In simple words: Oscillatoria, Nostoc, Anabaena, and Tolypothrix are types of blue-green algae that help both by making food and by providing nitrogen to soil.

🎯 Exam Tip: When listing examples, try to remember at least three to show broader knowledge of the category.

 

Question 39. Define organic farming.
Answer: Organic farming is a way of growing plants and raising animals using natural methods. It focuses on using biological materials and avoids man-made substances to keep the soil healthy and balance the environment. This helps to reduce pollution and waste, creating a healthier ecosystem for crops and animals.
In simple words: Organic farming is a natural way to grow food and raise animals, using only natural things to keep the soil healthy and avoid pollution.

🎯 Exam Tip: Keywords for organic farming include "natural methods," "biological materials," and "avoiding synthetic substances."

 

Question 40. Pseudomonas putida and pollution abatement – comment.
Answer: Pseudomonas putida is a special type of bacteria that has been changed by scientists (genetically engineered). It has many small rings of DNA called plasmids, which help it break down hydrocarbons found in oil spills. By digesting these harmful substances, it helps to clean up water pollution, making it a valuable tool for pollution abatement.
In simple words: Pseudomonas putida is a modified bacteria that can break down oil in water, helping to clean up pollution.

🎯 Exam Tip: Mentioning "genetically engineered" and its ability to degrade "hydrocarbons" are crucial points for this bacterium's role in pollution control.

 

Question 41. Complete the following equation by identifying the microbes involved in bioremediation.
\( \text{PET Plastics} \xrightarrow{A} \text{terephthalic acid, Ethylene glycol} \)
\( \text{Trichloro ethane} \xrightarrow{B} \text{Non-toxic ethane} \)
Answer:
A - Ideonella sakaiensis
B - Dehalococcoides species.
In simple words: For plastic, the bacteria Ideonella sakaiensis helps break it down. For trichloro ethane, Dehalococcoides species bacteria turn it into something safer. These microbes are like nature's cleanup crew, breaking down harmful substances.

🎯 Exam Tip: Always specify the exact microbe name for bioremediation processes, as different microbes specialize in different pollutants.

 

12th Bio Zoology Guide Microbes in Human Welfare Three Marks Questions and Answers

 

Question 1. Differentiate between Prebiotics and Probiotics.
Answer:
**Prebiotics:** These are types of fiber and natural compounds found in foods that our body cannot digest. Instead, they act as food for the good bacteria already living in our gut, helping them grow and become more active. An example is inulin, found in onions or bananas.
**Probiotics:** These are live microorganisms, usually good bacteria or yeasts, which give health benefits when eaten. They work by adding more helpful microbes to our gut, or by helping to bring back the natural balance of good bacteria. Yogurt is a good example of a food with probiotics.
In simple words: Prebiotics are food for good gut bacteria, while probiotics are the good gut bacteria themselves.

🎯 Exam Tip: Remember "Pre" for "food before" and "Pro" for "for life" (live microbes) to easily distinguish between them.

 

Question 2. How yogurt is produced?
Answer: Yogurt is made by a process called bacterial fermentation of milk. Specific bacteria, mainly Streptococcus thermophilus and Lactobacillus bulgaricus, are added to milk. These bacteria eat the lactose (sugar) in the milk and turn it into lactic acid. This lactic acid makes the milk thicken and gives yogurt its distinct sour taste and creamy texture. The acetaldehyde produced by these bacteria also gives yogurt its unique flavor.
In simple words: Yogurt is made by adding special bacteria to milk. These bacteria change the milk sugar into lactic acid, making the milk thick and sour, which is how yogurt is formed.

🎯 Exam Tip: Key points include "bacterial fermentation," "lactose to lactic acid," and the specific bacteria involved (Streptococcus thermophilus and Lactobacillus bulgaricus).

 

Question 3. Name the scientists who were awarded Nobel Prize in 1945 for discovering the penicillin drug & its role as an antibiotic.
Answer: The scientists awarded the Nobel Prize in 1945 for the discovery of penicillin and its role as an antibiotic were Alexander Fleming, Ernst Chain, and Howard Florey. Fleming first discovered penicillin, while Chain and Florey developed methods to purify and mass-produce it, making it usable as medicine. Penicillin revolutionized medicine by effectively treating bacterial infections.
In simple words: Alexander Fleming, Ernst Chain, and Howard Florey won the Nobel Prize for finding and developing penicillin, the first widely used antibiotic.

🎯 Exam Tip: While Fleming is credited with the initial discovery, remember Chain and Florey for their crucial work in making penicillin a practical medicine.

 

Question 4. Both Tetracycline and Streptomycin are broad-spectrum antibiotics yet functionally discriminate. How?
Answer: Both Tetracycline and Streptomycin are broad-spectrum antibiotics, meaning they can fight many types of bacteria. However, they work differently. Tetracycline is a bacteriostatic antibiotic, which means it stops bacteria from growing and multiplying, allowing the body's immune system to clear them. Streptomycin, on the other hand, is a bactericidal antibiotic; it actively kills the bacteria. These different ways of working mean they are used for various types of infections and bacterial strains.
In simple words: Both drugs fight many bacteria, but Tetracycline stops them from growing, while Streptomycin kills them directly.

🎯 Exam Tip: Clearly define bacteriostatic (stops growth) and bactericidal (kills) to explain the functional difference.

 

Question 5. Under which condition does a microbe gains resistance against antibiotics?
Answer: Microbes gain resistance against antibiotics when they develop ways to defeat the drugs meant to kill them or stop their growth. This often happens due to the overuse or misuse of antibiotics, where only the strongest microbes survive and multiply, passing on their resistance. Not following proper infection control also speeds this up. When resistance occurs, the antibiotic can no longer effectively treat the infection. Using antibiotics only when needed and as prescribed helps slow down this process.
In simple words: Microbes become resistant when they learn to fight off antibiotics, usually because antibiotics are used too much or incorrectly, letting strong microbes survive.

🎯 Exam Tip: Focus on "overuse," "misuse," and "natural selection" (survival of the fittest microbes) as key conditions leading to resistance.

 

Question 6. Write a short on “Pathaneer”.
Answer: Pathaneer is a traditional drink from South India, made by collecting sap from palm and coconut trees before their flower parts (spadices) open. It is a refreshing drink, and if boiled, it can be made into jaggery (palm sugar). If left for a few hours without boiling, the natural yeast in the air will ferment it into toddy, which contains about 4% alcohol. This process highlights traditional beverage production methods.
In simple words: Pathaneer is a sweet sap from palm trees, a refreshing drink that can also be made into jaggery or, if left to ferment, into toddy.

🎯 Exam Tip: Mentioning its origin from "palm and coconut trees," its ability to form "jaggery," and its fermentation into "toddy" are key details.

 

Question 7. Explain in simple about the production process of industrial alcohol.
Answer: Industrial alcohol, usually ethanol, is made by first grinding up a raw material like grains or molasses. Then, enzymes like amylase are added to break down the starch into simple sugars. After this, yeast is introduced, which ferments these sugars into ethanol. This raw ethanol is then purified by distillation, meaning it's heated to separate the alcohol from water, resulting in a high concentration (up to 96%) of ethanol. This alcohol is vital for many industries, including as a biofuel.
In simple words: Industrial alcohol is made by fermenting sugars from plants like corn or molasses using yeast, then purifying the alcohol.

🎯 Exam Tip: The core steps are "breaking down starch to sugars," "fermentation by yeast," and "distillation for purification."

 

Question 8. Write the percent of alcohol in Beer, Wine and Distilled spirits
Answer: The amount of alcohol varies across different beverages. Beer typically contains 3% to 5% alcohol. Wine usually has a higher alcohol content, ranging from 9% to 14%. Distilled spirits, which undergo a purification process after fermentation, have the highest concentration, typically between 35% and 50% alcohol. Distillation increases the alcohol concentration by separating it from water and other compounds.
In simple words: Beer has 3-5% alcohol, wine has 9-14%, and stronger drinks like whisky (distilled spirits) have 35-50%.

🎯 Exam Tip: Remember that distillation is the process that increases the alcohol concentration significantly in spirits compared to fermented beverages like beer and wine.

 

Question 9. Complete the table.

Answer:
A – Germinated Barley
B- Rum
C- Fermented sap of palm and coconut tree
D- Saccharomyces cerevisiae.
In simple words: This table shows which raw materials are turned into different drinks using specific yeast or fermenting agents. Each combination makes a unique product.

🎯 Exam Tip: Pay close attention to the specific type of yeast (e.g., Saccharomyces carlsbergensis vs. cerevisiae) as they can be associated with different products.

 

Question 10. Name the enzymes used as clarifier for Bottled juices.
Answer: The enzymes used to make bottled juices clear are pectinase, protease, and cellulase. These enzymes break down substances like pectin, proteins, and cellulose that make juices cloudy. By breaking these down, the enzymes help to remove the unwanted particles, making the juice transparent and appealing. This is important for juice manufacturers to ensure a clear product.
In simple words: Pectinase, protease, and cellulase are enzymes used to make bottled juices clear by breaking down cloudy parts.

🎯 Exam Tip: Remembering "pectinase" is key, as pectin is a common culprit for cloudiness in fruit juices.

 

Question 11. Write a short note on bio diesel.
Answer: Biodiesel is a type of fuel made from vegetable oils, animal fats, or used cooking greases. It can be used in diesel engines without needing to change the engine. Biodiesel is good for the environment because it is non-toxic, breaks down easily, and produces less air pollution than regular diesel. The Indian government has even identified plants like Jatropha curcas as good sources for making biodiesel. This renewable fuel offers a cleaner alternative to fossil fuels.
In simple words: Biodiesel is a clean fuel made from plant oils or animal fats, used in diesel engines, and is better for the environment than regular diesel.

🎯 Exam Tip: Highlight its source ("vegetable oils, fats, greases"), its environmental benefits ("non-toxic, biodegradable, lower pollution"), and its direct use in "diesel engines."

 

Question 12. Name the act enforced by government to conserve water bodies. Also mention its objectives.
Answer: The act enforced by the government to conserve water bodies is the National River Conservation Plan (NRCP), which was started in 1995. Its main goals are to improve the water quality of India's major rivers. This includes capturing raw sewage and diverting it for treatment, building sewage treatment plants, and constructing low-cost toilets to stop open defecation near river banks. This plan aims to keep our rivers clean and healthy.
In simple words: The National River Conservation Plan (NRCP), started in 1995, works to clean up India's rivers by treating sewage and stopping pollution.

🎯 Exam Tip: Ensure you name the act (NRCP) and list at least two of its core objectives, such as "sewage treatment" and "preventing open defecation."

 

Question 13. Give an account on MFC.
Answer: An MFC, or Microbial Fuel Cell, is a system that creates electricity using bacteria. It works like a tiny battery where bacteria break down organic matter, releasing electrons. Inside the MFC, there's an anode (negative side) where microbes oxidize fuel and produce protons and electrons. The protons go through a special membrane to the cathode (positive side), and the electrons travel through an outside circuit, creating electric current. This technology mimics natural bacterial processes to generate clean energy.
In simple words: A Microbial Fuel Cell (MFC) uses bacteria to break down organic waste, producing electricity in the process.

🎯 Exam Tip: Key components to mention are "bacteria," "organic matter," and the generation of "electric current" via "electrons" and "protons."

 

Question 14. How Bacillus thuringiensis provides insect resistance?
Answer: Bacillus thuringiensis, often called Bt, is a soil bacterium that produces a special toxin called cry toxin. When this bacterium is grown, it forms crystal proteins (Delta-endotoxins) that are harmful to certain insects but safe for humans and other animals. Scientists have taken the gene that makes this toxin (cry gene) and put it into crops like cotton, creating genetically engineered insect-resistant plants. When insects eat these plants, the toxin attacks their digestive system, paralyzing them and causing them to stop eating and eventually die. This provides a natural defense for the crops.
In simple words: Bacillus thuringiensis makes a special toxin that harms insects. Scientists put the gene for this toxin into crops, making the plants naturally resistant to insect pests.

🎯 Exam Tip: Focus on "cry toxin," "Delta-endotoxins," and how the "cry gene" is transferred to crops for insect resistance.

 

Question 15. Give an account on Weedicides.
Answer: Weedicides are substances used to kill weeds, which are unwanted plants that grow alongside crops, without harming the crops themselves. Bioweedicides are a type of weedicide made from natural sources like microbes (fungi, bacteria, or protozoa). For example, the first bioherbicide was developed in 1981 from a fungus called Phytophthora palmivora, which helps control specific weeds like the strangler vine in citrus farms. Using bioweedicides is an environmentally friendly way to manage weeds.
In simple words: Weedicides kill unwanted plants. Bioweedicides are natural versions made from microbes that target weeds without harming crops.

🎯 Exam Tip: Highlight that weedicides "destroy weeds without harming useful plants" and emphasize the environmental benefit of "bioweedicides" from microbes.

 

Question 16. What are the Bio-fertilizers? Mention their role in agriculture?
Answer: Bio-fertilizers are living microorganisms that are applied to plant surfaces or soil to enhance nutrient availability and uptake by plants. They help enrich the soil's nutrient quality by improving its physical and chemical properties, such as structure, water-holding capacity, and pH. They also provide nutrients like nitrogen and phosphorus, reducing the need for chemical fertilizers. Bacteria (like Rhizobium), fungi (like mycorrhiza), and cyanobacteria are common sources. For example, Rhizobium helps legumes fix nitrogen from the air, directly boosting soil fertility.
In simple words: Bio-fertilizers are helpful living microbes that make soil richer in nutrients and improve its quality, helping plants grow better.

🎯 Exam Tip: Remember that bio-fertilizers are "living microorganisms" and their main role is "enriching soil nutrient quality" and "improving soil properties."

 

Question 17. What is mycorrhiza? How does it benefit the plants?
Answer: Mycorrhiza is a beneficial partnership between a fungus and the roots of a plant. The fungus grows around or inside the plant roots. In this relationship, the fungus helps the plant by absorbing important nutrients like phosphorus from the soil and giving them to the plant. In return, the plant provides the fungus with sugars it makes through photosynthesis. Plants with mycorrhizal associations often grow better, are more resistant to diseases, and can tolerate tough conditions like drought and salty soil. This natural partnership boosts plant health significantly.
In simple words: Mycorrhiza is a helpful team-up between a fungus and plant roots, where the fungus helps the plant get more nutrients and grow stronger.

🎯 Exam Tip: Focus on it being a "symbiotic association" (beneficial to both), the fungus's role in "phosphorus absorption," and the plant's improved "growth and resilience."

 

Question 18. Write a brief note on Cyanobacteria & its significances.
Answer: Cyanobacteria, also known as blue-green algae (BGA), are simple, one-celled organisms that are like bacteria but can also perform photosynthesis, just like plants. They are very important because they can fix nitrogen from the air, turning it into a form plants can use. This makes them excellent natural fertilizers, especially in waterlogged paddy fields. They also produce growth-promoting substances like vitamins and amino acids, which help plants grow and produce more. Cyanobacteria were among the earliest forms of life on Earth, playing a crucial role in producing oxygen and shaping our planet's early atmosphere.
In simple words: Cyanobacteria are tiny organisms that act like plants and bacteria. They help make soil fertile by taking nitrogen from the air and also help plants grow.

🎯 Exam Tip: Key aspects are their dual nature (photosynthesis and nitrogen fixation), their role as "natural fertilizers," and their contribution to "plant growth promoters."

 

Question 19. Define bio-remediation and its types.
Answer: Bioremediation is the process of using living organisms, mainly microbes like bacteria or fungi, to clean up pollutants or contaminants from soil, water, or air. These organisms naturally break down harmful substances into less toxic or harmless forms. Bioremediation is often less expensive and more sustainable than other cleaning methods. There are two main types: 1. **In-situ bioremediation:** This happens directly at the polluted site, like treating contaminated soil or water without moving it. 2. **Ex-situ bioremediation:** This involves removing the contaminated material from its original place and treating it somewhere else, like in a special treatment facility. This process leverages the natural abilities of microbes to restore environmental health.
In simple words: Bioremediation uses tiny living things, like bacteria, to clean up pollution. It can be done right where the pollution is (in-situ) or by moving the polluted material to a different place for cleaning (ex-situ).

🎯 Exam Tip: Define bioremediation as "using living organisms to clean up pollutants" and clearly distinguish between "in-situ" (on-site) and "ex-situ" (off-site) types.

 

12th Bio Zoology Guide Microbes in Human Welfare Five Marks Questions and Answers

 

Question 1. Explain the role of microbes in the production of enzymes & bio-active molecules?
Answer: Microbes play a huge role in making many chemicals, enzymes, and special bioactive molecules that are important for industries and health. * **Organic Acids:** Many microbes produce different organic acids. For instance, Aspergillus niger makes citric acid (used in food and drinks), Acetobacter aceti makes acetic acid (vinegar), Rhizopus oryzae makes fumaric acid, Clostridium butyricum makes butyric acid, and Lactobacillus makes lactic acid. * **Enzymes:** Yeast (Saccharomyces cerevisiae) and various bacteria are used to make enzymes commercially. Lipases are enzymes from microbes that remove oily stains in detergents. Pectinase, protease, and cellulase are used to clarify bottled fruit juices by breaking down cloudy particles. Rennet, an enzyme, helps separate milk into solid curds for cheese making. * **Bioactive Molecules:** * **Streptokinase:** Produced by the bacterium Streptococcus, this is genetically engineered to be a "clot buster" drug. It is used to dissolve blood clots in patients who have had a heart attack. * **Cyclosporin A:** This is a powerful immunosuppressant produced by the fungus Trichoderma polysporum. It is used in organ transplant surgeries to prevent the patient's body from rejecting the new organ. It also has anti-inflammatory, anti-fungal, and anti-parasitic properties. * **Statins:** These cholesterol-lowering drugs are produced by the yeast Monascus purpureus. Statins work by blocking the enzyme responsible for making cholesterol, thus helping to reduce blood cholesterol levels and prevent heart disease. * **Human Insulin:** Recombinant human insulin, a vital hormone for diabetes treatment, is primarily produced using genetically engineered E. coli and Saccharomyces cerevisiae. These examples show how microbes are essential tiny factories for various useful products. They make a vast range of products, from simple enzymes to complex life-saving drugs.
In simple words: Microbes are like tiny workers that make many useful things. They produce acids for food, enzymes to clean or make cheese, and special medicines like clot-busters, drugs to stop organ rejection, and cholesterol-lowering medicines.

🎯 Exam Tip: For each microbe, clearly state the product it makes and its specific use or benefit. Categorize them into organic acids, enzymes, and bioactive molecules for a structured answer.

 

Question 2. Describe the stages of the Sewage treatment process.
Answer: Sewage treatment is usually performed in three main stages to clean wastewater before it is returned to the environment: 1. **Primary Treatment (Physical Removal):** This initial stage involves physically removing large and small particles from the sewage. * First, floating debris like plastic and rags are taken out by sequential filtration. * Then, the wastewater goes into large settling tanks where grit (soil and small pebbles) and other heavy solids settle down at the bottom. These settled solids form the "primary sludge." * The liquid part that remains after settling is called the "effluent" and is then moved on to the next stage. 2. **Secondary Treatment (Biological Treatment):** This stage uses biological processes to reduce the organic matter in the effluent. * The primary effluent is pumped into large aeration tanks. Here, it is continuously stirred, and air is pumped into it. * This encourages the growth of useful aerobic microbes (bacteria and fungi) that form "flocs" (masses of microbes). * These microbes consume the majority of the organic waste in the water, significantly reducing its Biological Oxygen Demand (BOD). BOD measures how much oxygen microbes would need to break down the organic matter; a lower BOD means less pollution. * The water then goes into a secondary settling tank, where the microbial flocs settle, forming "secondary sludge" or "activated sludge." A small part of this activated sludge is returned to the aeration tank to help new microbes grow. The rest goes to anaerobic digesters. 3. **Tertiary Treatment (Advanced Treatment):** This is the final stage, which further improves the water quality, making it suitable for reuse or safe release. * This stage removes remaining inorganic compounds, like nitrogen and phosphorus, that secondary treatment might miss. * UV radiation is often used here as a disinfectant to kill any remaining harmful microorganisms, as it is a chemical-free process and does not add chemicals to the water. This step ensures the treated water is free from pathogens. Through these stages, wastewater is transformed from a pollutant into water that can safely rejoin the natural water cycle, protecting aquatic ecosystems.
In simple words: Sewage treatment cleans dirty water in three steps: first, removing big pieces; second, using helpful microbes to eat tiny dirt; and third, cleaning it extra well, often with UV light, before returning it to nature.

🎯 Exam Tip: Clearly outline the three stages (Primary, Secondary, Tertiary), mentioning the key process for each (physical, biological, advanced/disinfection) and what is achieved (removal of large solids, reduction of BOD, removal of inorganic compounds/pathogens).

 

Question 3. How microbes are used in Gobar gas production?
Answer: Microbes are crucial for producing Gobar gas, also known as biogas. This gas is a mix of methane (about 63%), carbon dioxide, and hydrogen, created when organic matter breaks down without oxygen (anaerobic digestion). * **Raw Materials:** The main raw material for Gobar gas is cattle dung, often called "Gobar," along with agricultural waste, municipal waste, and other plant materials. * **Anaerobic Digestion:** These organic materials are put into a special airtight tank called a digester. Inside this tank, different types of microbes work together in three main stages: 1. **Solubilization:** First, bacteria break down complex organic materials into simpler, soluble compounds. 2. **Acidogenesis:** Next, other bacteria convert these soluble compounds into organic acids. 3. **Methanogenesis:** Finally, a special group of bacteria called methanogens (e.g., Methanobacterium) convert these acids into methane gas. Methanogens thrive in oxygen-free environments, making them perfect for this process. * **Products:** The biogas produced is then collected and can be used for cooking and lighting. The leftover material, known as slurry, is rich in nutrients and serves as an excellent organic fertilizer. This system provides both energy and fertilizer, making it a sustainable solution for rural areas.
In simple words: Microbes in a special tank break down cow dung and other waste without oxygen. This process creates methane gas for cooking and lighting, and the leftover material can be used as fertilizer.

🎯 Exam Tip: Emphasize "anaerobic digestion," the role of "methanogens," and the dual benefits of "fuel (biogas)" and "fertilizer (slurry)."

 

Question 4. Bioremediation & microbes – Discuss.
Answer: Bioremediation is an eco-friendly approach that uses microbes to clean up environmental pollution. Microbes, such as bacteria and fungi, possess natural abilities to break down or detoxify various pollutants. * **Aerobic Microbes:** In the presence of oxygen, aerobic microbes are effective at degrading pollutants like pesticides and hydrocarbons. A notable example is *Pseudomonas putida*, a genetically engineered microorganism (GEM). This bacterium, known for its multiple plasmids, can digest hydrocarbons in oil spills, proving invaluable in cleaning up contaminated sites. * **Anaerobic Microbes:** In environments without oxygen, anaerobic microbes also play a crucial role. For instance, *Dechloromonas aromatica* can break down benzene and oxidize toluene and xylene. *Dehalococcoides species* are used to convert toxic trichloroethene into non-toxic ethane. *Pestalotiopsis microspora*, an endophytic fungus, can even digest polyurethane. * **Other Microbes:** Nitrosomonas europaea helps degrade benzene and halogenated organic compounds. *Ideonella sakaiensis* is currently being explored for recycling PET plastics, using enzymes like PETase and MHETase to break them down into simpler components. * **Mechanisms:** These microbes break down pollutants through their metabolic processes, converting complex toxic substances into simpler, less harmful molecules like water and carbon dioxide. This biological approach is generally more sustainable and less invasive than chemical or physical cleanup methods. Bioremediation harnesses the diverse metabolic capabilities of microbial communities to restore contaminated environments.
In simple words: Bioremediation uses tiny living things like bacteria and fungi to clean up pollution. Some microbes work with oxygen to break down pesticides and oil, while others work without oxygen to change toxic chemicals into safe ones, making the environment cleaner.

🎯 Exam Tip: Structure your answer by distinguishing between aerobic and anaerobic microbes, providing specific examples for each, and mentioning the types of pollutants they target (hydrocarbons, pesticides, plastics, etc.).

 

Higher Order Thinking Skills (HOTs) Questions

 

Question 1. One can notice large holes in Swiss cheese. Which bacterium is responsible for these holes. What are these holes due to?
Answer: The bacterium responsible for the large holes in Swiss cheese is *Propionibacterium shermanii*. These holes, known as "eyes," are formed during the cheese-making process. The bacteria produce a large amount of carbon-di-oxide gas as they ferment the lactic acid in the cheese. This gas gets trapped in the cheese, creating bubbles that expand and form the distinct holes. This process not only creates the characteristic appearance but also contributes to the unique nutty flavor of Swiss cheese.
In simple words: The big holes in Swiss cheese are made by bacteria called Propionibacterium shermanii, which release a lot of carbon dioxide gas as they grow.

🎯 Exam Tip: Remember the specific bacterium *Propionibacterium shermanii* and that the holes are due to "carbon dioxide gas" production during fermentation.

 

Question 2. Name the resource agent of statins. How does this bioactive molecule functions in our body?
Answer: The resource agent for statins is the yeast *Monascus purpureus*. Statins are bioactive molecules that play a crucial role in managing cholesterol levels in our body. They function by competitively inhibiting the enzyme HMG-CoA reductase, which is responsible for cholesterol synthesis in the liver. By blocking this enzyme, statins reduce the production of cholesterol, thereby lowering the overall blood cholesterol level. This helps to prevent heart diseases caused by high cholesterol.
In simple words: Statins come from a yeast called Monascus purpureus. They work in our body by blocking an enzyme in the liver that makes cholesterol, which helps lower bad cholesterol levels.

🎯 Exam Tip: Identify *Monascus purpureus* as the source and explain that statins "inhibit cholesterol synthesis" by targeting a specific enzyme.

 

Question 3. Cyclosporin-A is an immuno supprenant. Suggest any one area where it can be used efficiently? Explan.
Answer: Cyclosporin-A is a powerful immunosuppressant, meaning it reduces the activity of the body's immune system. One area where it is used very efficiently is in **organ transplant surgeries**. When a patient receives an organ from another person, their immune system naturally recognizes it as foreign and tries to attack and reject it. Cyclosporin-A helps prevent this graft rejection by suppressing the immune response, allowing the transplanted organ to be accepted by the body. This significantly improves the success rate of organ transplants.
In simple words: Cyclosporin-A weakens the body's immune system. It's very useful after organ transplants to stop the body from rejecting the new organ.

🎯 Exam Tip: The key application for Cyclosporin-A as an immunosuppressant is "organ transplant surgeries" to "prevent graft rejection."

 

Question 4. Name the blank spaces a, b, and c of the given table:

Answer:
(a) Clostridium butyricum
(b) Fungus
(c) Cyclosporin A
In simple words: This table shows that different microbes make different useful products. Clostridium butyricum (a bacterium) makes butyric acid. Aspergillus niger (a fungus) makes citric acid. Trichoderma polysporum (a fungus) makes Cyclosporin A.

🎯 Exam Tip: Be precise with the microbe names and their corresponding products; many microbes produce unique substances.

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