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Microorganisms & Human Health

Bacteria, viruses, fungi, immunity, vaccines, diseases

Key Concepts
  • Bacteria: prokaryotes; reproduce by binary fission; gram-positive vs gram-negative
  • Viruses: protein coat (capsid) around nucleic acid; require host cell to replicate
  • Beneficial microbes: Lactobacillus (yogurt), Rhizobium (N₂ fixation), Aspergillus (citric acid)
  • Harmful microbes: Plasmodium (malaria), Mycobacterium tuberculosis (TB), Vibrio cholerae (cholera)
  • Antibiotics: produced by microbes; kill or inhibit bacteria; penicillin from Penicillium notatum
Important Formulae
Bacterial growth (exponential phase) N = N₀ × 2ⁿ (n = number of generations)
Quick Tips
  • Koch's postulates: 4 criteria to establish causative link between microbe and disease.
  • Pasteur's experiment disproved spontaneous generation using swan-neck flask.
  • Biogas: mixture of methane (~70%) and CO₂ produced by anaerobic bacteria from organic waste.
Sample Practice Questions

  1. Biogas is produced by methanogenic bacteria decomposing:

    • Coal
    • Organic waste in anaerobic conditions
    • Petroleum
    • Sewage in aerobic conditions
    Show answer

    Answer: Organic waste in anaerobic conditions

  2. Aflatoxins are toxic compounds produced by:

    • E. coli
    • Salmonella
    • Aspergillus flavus (fungus)
    • Clostridium botulinum
    Show answer

    Answer: Aspergillus flavus (fungus)

  3. Viroids are infectious agents consisting of:

    • DNA only
    • Naked RNA (no protein coat)
    • RNA + protein coat
    • Protein only (prion)
    Show answer

    Answer: Naked RNA (no protein coat)

  4. Baker's yeast (Saccharomyces cerevisiae) ferments glucose to produce:

    • Lactic acid only
    • Acetic acid and water
    • Ethanol and CO₂
    • Methane and CO₂
    Show answer

    Answer: Ethanol and CO₂

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Practice Questions

Practice 20 randomly selected NEET questions on Microorganisms & Human Health. Answers are revealed after each question.

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