Questions & explanations
1. Why is cancer considered a major cause of death globally?
- It is caused by a single virus that infects everyone.
- It results from the uncontrolled division of abnormal cells that can spread through the body.
- It is highly contagious and spreads from person to person.
- It can be easily cured with a course of antibiotics.
Answer: It results from the uncontrolled division of abnormal cells that can spread through the body.
Cancer is dangerous because of uncontrolled division of abnormal cells. These cells lose normal growth control, form tumours, and malignant tumours can spread (metastasise) to other organs, disrupting their function and often causing death. Cancer is not contagious, is not caused by a single virus that infects everyone, and antibiotics (which act on bacteria) have no effect on it.
2. The principle of vaccination is based on:
- The ability of antibodies to neutralize toxins
- The memory property of the immune system
- The immediate production of antibodies
- The destruction of pathogens by macrophages
Answer: The memory property of the immune system
Vaccination works by introducing antigens that stimulate the immune system to produce memory cells, which provide long-term protection upon re-exposure. Antibody neutralization is a mechanism, but the core principle is immunological memory. Immediate production is not typical; vaccines take time. Macrophages are involved but not the principle.
3. Which of the following is an effective measure for preventing drug and alcohol abuse among adolescents?
- Avoiding undue peer pressure
- Increasing pocket money
- Encouraging late-night parties
- Promoting competitive exams without breaks
Answer: Avoiding undue peer pressure
Avoiding undue peer pressure helps adolescents resist the temptation to try drugs or alcohol, as peer pressure is a major risk factor. The other options (increasing pocket money, encouraging late-night parties, and promoting competitive exams without breaks) are not preventive measures and may actually increase stress or access to substances.
4. Why is tissue matching necessary before organ transplantation?
- To prevent blood clotting
- To ensure the organ functions properly
- To avoid rejection by the recipient's immune system
- To match blood type only
Answer: To avoid rejection by the recipient's immune system
Tissue matching is done to minimize the risk of graft rejection, which is mediated by the cell-mediated immune response. The immune system recognizes foreign tissues and attacks them. Blood clotting and organ function are not directly related to tissue matching. Blood type matching is part of it, but tissue matching includes HLA typing.
5. Which of the following practices is most effective in preventing the spread of infectious diseases like cholera and typhoid?
- A) Consuming only organic vegetables without washing them
- B) Proper disposal of waste and excreta along with periodic disinfection of water reservoirs
- C) Avoiding bathing to conserve water
- D) Using insecticides only when disease symptoms appear
Answer: B) Proper disposal of waste and excreta along with periodic disinfection of water reservoirs
Proper disposal of waste and excreta prevents contamination of water sources, and periodic disinfection of water reservoirs kills pathogens, directly reducing the transmission of waterborne diseases like cholera and typhoid. The other options either do not prevent infection (A, C) or are reactive rather than preventive (D).
6. Rheumatoid arthritis is an example of which type of immune disorder?
- Allergy
- Autoimmune disease
- Immunodeficiency
- Hypersensitivity type I
Answer: Autoimmune disease
Rheumatoid arthritis is an autoimmune disorder where the immune system mistakenly attacks self-cells, particularly in joints, causing inflammation and damage. It is not an allergy (which involves external allergens), immunodeficiency (lack of immune response), or type I hypersensitivity (immediate allergy).
7. Which of the following symptoms is commonly associated with the common cold and typically lasts for 3 to 7 days?
- Nasal congestion and discharge
- Severe joint pain
- Persistent high fever with chills
- Skin rash
Answer: Nasal congestion and discharge
The common cold typically presents with nasal congestion, discharge, sore throat, cough, and headache, lasting 3–7 days. Severe joint pain, persistent high fever with chills, and skin rash are not characteristic of the common cold; they are more typical of other infections like dengue or chikungunya.
8. Which of the following best describes the mechanism of an allergic reaction?
- Release of histamine and serotonin from mast cells triggered by allergens
- Attack of self-cells by the immune system due to genetic factors
- Overproduction of antibodies against bacterial antigens
- Activation of T-cells against viral pathogens
Answer: Release of histamine and serotonin from mast cells triggered by allergens
Allergy is an exaggerated immune response to environmental allergens like pollen or dust. These allergens cause mast cells to release chemicals such as histamine and serotonin, leading to allergic symptoms. The other options describe autoimmunity, bacterial infection, or viral response, not allergy.
9. Active immunity involves:
- Direct injection of preformed antibodies
- Production of antibodies by the host after exposure to antigens
- Transfer of antibodies from mother to fetus
- Administration of antitoxins
Answer: Production of antibodies by the host after exposure to antigens
Active immunity is characterized by the host's own immune system producing antibodies in response to antigen exposure. Direct injection of preformed antibodies is passive immunity. Transfer from mother to fetus is natural passive immunity. Antitoxins are preformed antibodies, hence passive.
10. Which of the following is a symptom of ascariasis?
- Internal bleeding and anaemia
- Dry scaly lesions on the scalp
- Chronic inflammation of lymphatic vessels
- Stools with mucus and blood clots
Answer: Internal bleeding and anaemia
Ascariasis, caused by Ascaris worms, can lead to internal bleeding, muscular pain, fever, anaemia, and intestinal blockage. Dry scaly lesions are typical of ringworm, chronic lymphatic inflammation is seen in filariasis, and stools with mucus and blood are characteristic of amoebiasis.
11. How is ascariasis typically transmitted to a healthy person?
- Through contaminated water, vegetables, and fruits
- By the bite of a female mosquito
- Through the air via respiratory droplets
- By direct contact with infected skin lesions
Answer: Through contaminated water, vegetables, and fruits
Ascaris eggs are excreted in faeces and contaminate soil, water, and plants. Infection occurs through ingestion of contaminated food or water. Mosquito bites transmit filariasis, respiratory droplets transmit many respiratory infections, and direct skin contact transmits ringworm.
12. Which of the following is a symptom of amoebiasis?
- Stools with excess mucus and blood clots
- Persistent cough with blood-tinged sputum
- Painless swelling of the lower limbs
- Dry, scaly lesions on the skin
Answer: Stools with excess mucus and blood clots
Amoebiasis symptoms include constipation, abdominal pain, and stools with excess mucus and blood clots. The other options are symptoms of other diseases: cough with blood suggests tuberculosis, swelling of limbs suggests filariasis, and dry scaly lesions suggest ringworm.