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Q9:
Do you think microbes can also be used as source of energy? If yes, how?
Solution :
Theoretical Foundation: Microbial Bioenergetics
Yes, microbes serve as significant sources of energy through metabolic pathways that convert organic biomass into combustible gases or electricity. This process primarily involves the anaerobic degradation of organic matter, a phenomenon leveraged in industrial biotechnology to produce biofuels and bio-electrochemical energy.
Step 1: Methane Production (Biogas)
Methanogenic archaea (e.g., Methanobacterium) perform anaerobic respiration in an oxygen-depleted environment, such as a biogas plant. The process occurs in three distinct phases:
- Hydrolysis: Complex polymers (carbohydrates, proteins, fats) are broken down into monomers.
- Acidogenesis: Monomers are converted into volatile fatty acids and alcohols.
- Methanogenesis: Methanogens utilize the intermediates to produce methane ($CH_4$) and carbon dioxide ($CO_2$).
The chemical conversion can be summarized as: $CO_2 + 4H_2 \rightarrow CH_4 + 2H_2O$ [Per the principle of Anaerobic Metabolism].
Step 2: Hydrogen Production (Bio-hydrogen)
Certain phototrophic and fermentative bacteria (e.g., Clostridium butyricum, Rhodobacter sphaeroides) can generate molecular hydrogen ($H_2$) via:
- Photo-fermentation: Using light energy to split organic acids into $H_2$.
- Dark Fermentation: Utilizing the enzyme hydrogenase to evolve $H_2$ gas during glucose metabolism.
Step 3: Microbial Fuel Cells (MFCs)
Microbial Fuel Cells represent a bio-electrochemical system where microbes act as catalysts to oxidize organic matter and transfer electrons directly to an anode, generating electric current.
Comparative Analysis of Microbial Energy Sources
| Source | Microbial Agent | Primary Product |
|---|---|---|
| Biogas Digester | Methanobacterium | $CH_4$ (Methane) |
| Bio-hydrogen | Clostridium | $H_2$ (Hydrogen Gas) |
| Microbial Fuel Cell | Geobacter | Electricity ($e^-$ flow) |
Synthesis of Mechanism
The ability of microbes to serve as energy sources rests on their capacity to perform redox reactions [Per the First and Second Laws of Thermodynamics]. By harnessing the high energy stored in chemical bonds of organic waste, microbes redistribute electrons to create stable, energy-dense molecules like $CH_4$ or facilitate the movement of electrons through an external circuit, thereby converting chemical energy into electrical or thermal energy.
Final Solution: Yes, microbes are a viable source of energy through the production of biogas (methane) via methanogenesis, generation of hydrogen gas through microbial fermentation, and the direct production of electricity via Microbial Fuel Cells (MFCs).
More Questions from Class 12 Biology Microbes in Human Welfare EXERCISES
- Q1: Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
- Q1: Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
- Q2: Give examples to prove that microbes release gases during metabolism.
- Q2: Give examples to prove that microbes release gases during metabolism.
- Q3: In which food would you find lactic acid bacteria? Mention some of their useful applications.
- Q3: In which food would you find lactic acid bacteria? Mention some of their useful applications.
- Q4: Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
- Q4: Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
- Q5: In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
- Q5: In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
- Q6: Name any two species of fungus, which are used in the production of the antibiotics.
- Q6: Name any two species of fungus, which are used in the production of the antibiotics.
- Q7: What is sewage? In which way can sewage be harmful to us?
- Q7: What is sewage? In which way can sewage be harmful to us?
- Q8: What is the key difference between primary and secondary sewage treatment?
- Q8: What is the key difference between primary and secondary sewage treatment?
- Q9: Do you think microbes can also be used as source of energy? If yes, how?
- Q10: Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
- Q10: Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
- Q11: Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled \(A\), \(B\) and \(C\); but the laboratory attendant did not note which was which. The BOD values of the three samples \(A\), \(B\) and \(C\) were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
- Q11: Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled (A), (B) and (C); but the laboratory attendant did not note which was which. The BOD values of the three samples (A), (B) and (C) were recorded as (20mg/L), (8mg/L) and (400mg/L), respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
- Q12: Find out the name of the microbes from which Cyclosporin \(A\) (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
- Q12: Find out the name of the microbes from which Cyclosporin (A) (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
- Q13(a): Find out the role of microbes in the following and discuss it with your teacher. (a) Single cell protein (SCP)
- Q13(a): Find out the role of microbes in the following and discuss it with your teacher. (a) Single cell protein (SCP)
- Q13(b): Find out the role of microbes in the following and discuss it with your teacher. (b) Soil
- Q13(b): Find out the role of microbes in the following and discuss it with your teacher. (b) Soil
- Q14: Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
- Q14: Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
- Q15: How do biofertilisers enrich the fertility of the soil?
- Q15: How do biofertilisers enrich the fertility of the soil?
CBSE Solutions for Class 12 Biology Microbes in Human Welfare
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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