NEET Biology Human Health and Disease MCQs Set 04

Answer: (c) Human RBC

Explanation:
1. Merozoites infect red blood cells and some develop into gametocytes there.
2. The gametocytes are taken up by a female Anopheles mosquito, where fertilisation occurs in the gut.

Teacher's Note:
1. Gametocytes form in human RBCs and mate in the mosquito gut.
2. Sporozoites are found in the mosquito salivary gland.

Answer: (b) B: Light chain, does not help in paratope formation

Explanation:
1. An antibody has two heavy and two light chains joined by disulfide bonds.
2. The paratope (antigen-binding site) is formed by the variable regions of both a heavy chain and a light chain.
3. So the statement that the light chain does not help in paratope formation is wrong.

Teacher's Note:
1. Each arm of the Y has one antigen-binding site made by a light and a heavy chain together.
2. Each polypeptide chain has one N-terminal and one C-terminal.

Answer: (d) The 'good humor' hypothesis was proposed by William Harvey

Explanation:
1. The humor (body fluid) theory of health was proposed in ancient Greece, associated with Hippocrates.
2. William Harvey is known for describing blood circulation.
3. The other statements are correct.

Teacher's Note:
1. Health was once explained by balance of body humors.
2. Harvey is linked with circulation of blood.

Answer: (b) HIV replicates in the host cell with the help of reverse transcriptase enzyme

Explanation:
1. HIV is a retrovirus. Its RNA is copied into DNA by reverse transcriptase inside the host cell.
2. Dysentery, plague and diphtheria are bacterial, ringworm is common in humid summer and rainy conditions, and the Widal test is for typhoid.

Teacher's Note:
1. Reverse transcriptase makes DNA from the RNA genome.
2. The Widal test diagnoses typhoid.

Answer: (c) They are virus specific

Explanation:
1. Interferons are small proteins secreted by virus infected cells.
2. They protect neighbouring cells against many different viruses, so they are not virus specific.

Teacher's Note:
1. Interferons form part of innate immunity (cytokine barriers).
2. They are not specific to any one virus.

Answer: (c) NK cells

Explanation:
1. Natural killer cells release perforins that make pores in the membrane of infected cells and microbes.
2. Neutrophils, macrophages and monocytes destroy microbes by phagocytosis.

Teacher's Note:
1. NK cells are cytotoxic lymphocytes of innate immunity.
2. They kill by perforin and not by engulfing.

Answer: (d) Smack, crack and marijuana are cannabinoids which interact with receptors mainly present in the brain

Explanation:
1. Only marijuana, hashish, charas and ganja are cannabinoids.
2. Smack is a derivative of morphine and crack is a form of cocaine.
3. The other three statements are correct.

Teacher's Note:
1. Benign tumours are not cancerous.
2. Cannabinoids act on cannabinoid receptors in the brain.

Answer: (b) A-(i), B-(iv), C-(ii), D-(iii)

Explanation:
1. T-lymphocytes mature in the thymus, so A matches (i).
2. B-lymphocytes mature in the bone marrow, so B matches (iv).
3. Peyer's patches lie in the small intestine, so C matches (ii).
4. MALT is a group of lymphoid tissue, so D matches (iii).

Teacher's Note:
1. Primary lymphoid organs are bone marrow and thymus.
2. MALT is mucosa-associated lymphoid tissue.

Answer: (d) Chikungunya, filariasis, malaria

Explanation:
1. Chikungunya, filariasis and malaria are transmitted by mosquitoes.
2. The other groups spread through food and water, droplets or contact.

Teacher's Note:
1. Mosquitoes carry many vector-borne diseases.
2. Vector control reduces these diseases.

Answer: (d) Amphetamines \(-\) Depressant

Explanation:
1. Amphetamines stimulate the central nervous system.
2. They are stimulants, not depressants.
3. The other three pairs are correctly matched.

Teacher's Note:
1. Barbiturates and tranquilisers are depressants.
2. Stimulants increase alertness and activity.

Answer: (b) IgE

Explanation:
1. IgE binds to mast cells. On contact with an allergen, the mast cells release histamine.
2. This causes the symptoms of allergy.

Teacher's Note:
1. IgE is also raised in worm infections.
2. Antihistamines reduce allergic symptoms.

Answer: (c) Single strand RNA

Explanation:
1. HIV is a retrovirus with two identical copies of single-stranded RNA.
2. Reverse transcriptase makes DNA from this RNA inside the host cell.

Teacher's Note:
1. Retroviruses have an RNA genome.
2. Their DNA copy integrates into the host genome.

Answer: (d) HIV selectively infects and kills B-lymphocytes

Explanation:
1. HIV infects helper T-lymphocytes, and also macrophages.
2. The fall in the number of helper T cells weakens immunity.
3. The other three statements are correct.

Teacher's Note:
1. Helper T cells are the main target of HIV.
2. The CD4 count falls as the disease advances.

Answer: (d) A strong magnetic field and non-ionising radiation

Explanation:
1. MRI uses a strong magnetic field and non-ionising radio waves to form images of body tissues.
2. It does not use X-rays.

Teacher's Note:
1. MRI can detect small changes in tissues.
2. CT scans use X-rays, which are ionising.

Answer: (c) B-lymphocytes

Explanation:
1. Neutrophils, macrophages and NK cells are cells of innate immunity.
2. B-lymphocytes produce specific antibodies and belong to acquired immunity.

Teacher's Note:
1. Innate immunity is non-specific.
2. Lymphocytes provide the specific, memory-based response.

Answer: (b) Physiological barriers

Explanation:
1. Saliva, tears, sweat and stomach acid prevent growth of microbes.
2. These are physiological barriers of innate immunity.

Teacher's Note:
1. Skin is a physical barrier.
2. Interferons are cytokine barriers.

Answer: (d) Surgery, irradiation and chemotherapy

Explanation:
1. Treatment of cancer usually combines surgery, radiation therapy and chemotherapy.
2. Immunotherapy using biological response modifiers such as \(\alpha\)-interferon is also used.

Teacher's Note:
1. Different methods are combined for the best result.
2. Early detection improves the chance of cure.

Answer: (c) Cytokine barriers

Explanation:
1. Virus infected cells secrete interferons, which protect non-infected cells from viral infection.
2. These proteins form the cytokine barriers of innate immunity.

Teacher's Note:
1. Cytokine barriers are chemical signals.
2. Interferons are also used as drugs against some cancers.

Answer: (d) Saliva of infected female Anopheles mosquito

Explanation:
1. Sporozoites collect in the salivary glands of the female Anopheles mosquito.
2. They are injected into the human when the mosquito bites.

Teacher's Note:
1. Only female Anopheles mosquitoes transmit malaria.
2. Sporozoites are the infective stage for humans.

Answer: (a) 2

Explanation:
1. An antibody has four polypeptide chains, two heavy and two light.
2. Each arm of the Y holds one antigen-binding site, so there are two.

Teacher's Note:
1. The two sites are on the tips of the two arms.
2. Each site binds one epitope.