Chapter 8: Human Health and Disease

Q1. What is the difference between innate and acquired immunity?

Solution

Innate: Present from birth, non-specific (e.g., skin, stomach acid, WBCs)
Acquired: Developed after exposure, specific (e.g., antibodies, memory cells)

Q2. How does the body fight a bacterial infection?

Solution

1. Phagocytes engulf bacteria (phagocytosis)
2. B-cells produce antibodies (IgM, IgG)
3. Complement system activates
4. Opsonization marks bacteria for destruction
5. Memory cells provide long-term immunity

Q3. What are allergens? How do they cause allergic reactions?

Solution

Allergens are substances that cause exaggerated immune responses (allergies). Upon first exposure, they stimulate IgE production. On re-exposure, allergens bind to IgE on mast cells, triggering release of histamine, causing symptoms like sneezing, itching, and swelling.

Q4. What is cancer? Distinguish between benign and malignant tumors.

Solution

Benign: Localized, does not spread, non-cancerous
Malignant: Invades surrounding tissues, spreads through metastasis, cancerous

Q5. What are the types of immunity? Explain active and passive immunity.

Solution

Active: Body produces antibodies (long-lasting) - Natural (infection) or Artificial (vaccination)
Passive: Ready-made antibodies transferred (short-term) - Natural (mother's milk) or Artificial (antiserum)

Q6. What is AIDS? How is HIV transmitted?

Solution

Transmission: (1) Sexual contact (2) Blood transfusion (3) Sharing needles (4) Mother to child
NOT transmitted by: Casual contact, mosquito bites, sharing food

Q7. What are vaccines? How do they work?

Solution

Working: (1) Antigen enters body (2) Immune system produces antibodies and memory cells (3) On re-exposure, memory cells respond rapidly
Examples: BCG (TB), Polio, MMR, Hepatitis B, DPT

Q8. What are the stages and symptoms of malaria?

Solution

Stages: (1) Liver stage (2) Blood stage (3) Gametocyte stage
Symptoms: High fever with chills and sweating, headache, anemia, spleen enlargement
Vector: Female Anopheles mosquito

Q9. What is autoimmunity? Give examples.

Solution

Examples: (1) Rheumatoid arthritis (2) Type 1 diabetes (3) Myasthenia gravis (4) Lupus

Q10. What are the effects of drugs and alcohol on the body?

Solution

Alcohol: Liver damage (cirrhosis), brain damage, addiction
Drugs: Heroin - respiratory depression; Cocaine - cardiac problems; Barbiturates - slow CNS
General: Organ damage, addiction, social problems

Q11. What is the difference between humoral and cell-mediated immunity?

Solution

Humoral: B-cells, antibodies (against extracellular pathogens)
Cell-mediated: T-cells, no antibodies (against intracellular pathogens, cancer, transplants)

Q12. What is the life cycle of Plasmodium?

Solution

In mosquito: Gametocytes → Gametes → Zygote → Oocyst → Sporozoites
In human: Sporozoites → Liver → Merozoites → RBCs → Gametocytes

Q13. What is an antigen and an antibody?

Solution

Antigen: Substance that triggers immune response
Antibody: Y-shaped protein produced by B-cells in response to antigen
Interaction: Antibodies bind antigens forming antigen-antibody complex

Q14. What is typhoid? Name the causative organism.

Solution

Organism: Salmonella typhi
Symptoms: High fever, headache, stomach pain, constipation, weakness
Diagnosis: Widal test
Transmission: Contaminated food and water

Q15. What is pneumonia?

Solution

Causative: Streptococcus pneumoniae, Haemophilus influenzae
Symptoms: Fever with chills, cough, difficulty breathing, chest pain
Transmission: Airborne droplets

← Chapter 7: Evolution Chapter 9: Strategies for Enhancement in Food Production →

← All Class 12 Biology Chapters