Human Health and Disease — Class 12 Biology NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 12 Biology chapter "Human Health and Disease" — 5 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 12 Biology chapter "Human Health and Disease" — 5 important questions with detailed answers for CBSE board…

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Key Questions Covered:

  1. Define disease. Explain the difference between infectious and non-infectious …
  2. Explain the symptoms and transmission of AIDS. How is HIV different from AIDS?
  3. Explain the concept of immunity. Distinguish between innate and adaptive immu…
  4. Explain allergies and hypersensitivity reactions. What are autoimmune diseases?
  5. Explain cancer at cellular and molecular level. What are oncogenes and tumor …

Solutions Summary:

Question Status
Define disease. Explain the difference between infectious… ✓ Solved
Explain the symptoms and transmission of AIDS. How is HIV… ✓ Solved
Explain the concept of immunity. Distinguish between inna… ✓ Solved
Explain allergies and hypersensitivity reactions. What ar… ✓ Solved
Explain cancer at cellular and molecular level. What are … ✓ Solved

Showing 5 of 5 questions

Q1: Define disease. Explain the difference between infectious and non-infectious diseases with examples.

Disease: Abnormal condition of body or part of body, characterized by symptoms and impaired function. Disruption of normal physiology. Infectious diseases: Definition: Diseases caused by pathogens (disease-causing organisms or toxins) transmissible from infected person to healthy person. Causative agents: - Bacteria: single-celled prokaryotes - Viruses: obligate intracellular parasites (RNA or DNA) - Fungi: eukaryotic organisms - Protozoa: single-celled eukaryotes - Parasitic worms: multicell...

Q2: Explain the symptoms and transmission of AIDS. How is HIV different from AIDS?

HIV (Human Immunodeficiency Virus) and AIDS (Acquired Immune Deficiency Syndrome): HIV vs AIDS: HIV: - Virus causing infection - Attacks CD4+ T cells (helper T cells), macrophages, dendritic cells - Can be present without symptoms - Treatable with antiretroviral therapy (ART) - Does not necessarily mean AIDS AIDS: - Clinical syndrome resulting from severe CD4+ T cell depletion - CD4+ count below 200 cells/μL (or <14% of lymphocytes) - Opportunistic infections and cancers develop - Without ...

Q3: Explain the concept of immunity. Distinguish between innate and adaptive immunity.

Immunity: Ability of body to resist infection and disease. Protection against pathogens and toxins through immune system. Innate (Non-specific) Immunity: Definition: Inborn, non-specific defense against all pathogens. First line of defense. Requires no prior exposure to pathogen. No memory of infection. Characteristics: - Present from birth - Non-specific (responds to many pathogens) - Rapid response (hours) - No memory (same response to repeated exposure) - Does not improve with repeated exp...

Q4: Explain allergies and hypersensitivity reactions. What are autoimmune diseases?

Allergies and hypersensitivity: Allergy (Hypersensitivity): Exaggerated immune response to harmless antigen (allergen). Immune system overreacts causing tissue damage. Types of hypersensitivity reactions: 1. Type I (Immediate hypersensitivity, IgE-mediated): - Onset: within minutes - Mechanism: * Previous exposure sensitizes immune system * IgE antibodies bind to mast cells and basophils * Re-exposure to allergen cross-links IgE on mast cells * Triggers degranulation...

Q5: Explain cancer at cellular and molecular level. What are oncogenes and tumor suppressors?

Cancer: Malignant disease characterized by uncontrolled cell growth, invasion of surrounding tissues, and metastasis (spreading to distant sites). Results from accumulation of mutations in genes controlling cell growth and death. Characteristics of cancer cells: 1. Loss of growth control: - Uncontrolled cell division - Ignore growth-inhibitory signals - Escape from contact inhibition - Form multilayered growth 2. Immortality: - Unlimited replicative potential - Telomerase re...

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