Microorganisms : Friend and Foe — Question 7
Back to all questionsQuestion 2(f)
The process of conversion of sugar into alcohol is called
- nitrogen fixation
- moulding
- fermentation
- infection
fermentation
Reason — The process of conversion of sugar into alcohol is known as fermentation. It is done by yeast.
Key Concepts Covered
This question tests your understanding of the following concepts from the chapter Microorganisms : Friend and Foe: Question, Conversion, Sugar, Alcohol, Nitrogen, Fixation. These are fundamental topics in Science that students are expected to master as part of the CBSE Class 8 curriculum.
A thorough understanding of these concepts will help you answer similar questions confidently in your CBSE examinations. These topics are frequently tested in both objective and subjective sections of Science papers. We recommend revising the relevant section of your textbook alongside practising these solved examples to build a strong foundation.
How to Approach This Question
Read the question carefully and identify what is being asked. Break down complex questions into smaller parts. Use the terminology and concepts discussed in this chapter. Structure your answer logically — begin with a definition or key statement, then provide supporting details. Review your answer to ensure it addresses all parts of the question completely.
Key Points to Remember
- Read the question carefully and identify all parts before answering.
- Use the terminology specific to this subject and chapter.
- Review the textbook content for this chapter before attempting questions.
- Practice writing concise, well-structured answers within time limits.
Practice more questions from Microorganisms : Friend and Foe — Science, Class 8 CBSE
Chapter Overview: Microorganisms: Friend and Foe
Microorganisms are tiny living organisms visible only under a microscope. This chapter classifies them into five groups (bacteria, viruses, fungi, protozoa, algae) and explores their dual role as both beneficial (food production, medicine, agriculture) and harmful (causing diseases). Food preservation methods and the nitrogen cycle are key examination topics.
Board Exam Weightage: 5-7 marks | Difficulty: Moderate
Key Formulas & Concepts
| Concept | Details |
|---|---|
| Fermentation | Sugar converted to alcohol + CO2 by yeast (anaerobic process) |
| Pasteurisation | Heating milk to 70°C for 15-30 seconds, then rapid cooling |
| Nitrogen Fixation | N2 (atmospheric) converted to NH3/NO3- by Rhizobium or lightning |
| Antibiotics | Medicines that kill or stop growth of disease-causing bacteria; e.g., Penicillin from Penicillium |
Must-Know Concepts
- Viruses are not truly living; they reproduce only inside host cells
- Lactobacillus converts milk to curd by producing lactic acid
- Yeast is used in bread making (CO2 makes dough rise) and alcohol production
- Rhizobium in legume root nodules fixes atmospheric nitrogen
- Female Anopheles mosquito transmits malaria (Plasmodium)
- Antibiotics work ONLY against bacteria, NOT against viruses
Types of Microorganisms
| Type | Cell Structure | Unicellular/Multicellular | Examples |
|---|---|---|---|
| Bacteria | Prokaryotic | Unicellular | Lactobacillus, Rhizobium, Salmonella |
| Fungi | Eukaryotic | Both | Yeast, Penicillium, Mushroom |
| Protozoa | Eukaryotic | Unicellular | Amoeba, Plasmodium, Paramecium |
| Algae | Eukaryotic | Both | Chlamydomonas, Spirogyra |
| Virus | Non-cellular | Neither | Influenza virus, HIV, TMV |
Common Mistakes to Avoid
- Calling viruses living organisms (they are borderline)
- Thinking all bacteria are harmful (many are very useful)
- Confusing antibiotics (treat bacteria) with vaccines (prevent diseases)
- Believing antibiotics can cure viral infections
Scoring Tips
- Create a disease-pathogen-transmission table for quick reference
- Learn the nitrogen cycle as a flow diagram with all 5 steps
- Remember preservation methods using everyday kitchen examples
- Focus on NCERT exercise questions on food preservation
Frequently Asked Questions
Q: How many marks does this chapter carry in the exam?
A: Approximately 5-7 marks in the annual exam.
Q: What question types are commonly asked?
A: MCQs (1 mark), Very Short Answer (2 marks), Short Answer (3 marks), and Long Answer / Diagram (5 marks).
Q: Is this chapter important for competitive exams?
A: Yes, concepts from this chapter appear in NTSE, Olympiad, and other science competitions.