Human Health and Disease

37 solved questions from Class 12 Biology, each with the full working. Tap any question to see the step-by-step solution.

• 1 What is the primary topic or theoretical principle explored in 'Human Health and Disease' (Class 12 BIOLOGY)? medium MCQ Chapter Core Principle
• 2 Which key mechanism or analytical rule is highlighted in 'Human Health and Disease'? medium MCQ Key Analytical Mechanism
• 3 What is the primary topic or principle explained in 'Human Health and Disease' (Class 12 Biology)? medium MCQ Chapter Core Concept
• 4 Which key observation or fact is central to understanding 'Human Health and Disease'? medium MCQ Key Fact & Mechanism
• 5 Why is the study of 'Human Health and Disease' important for students of Class 12? medium MCQ Learning Significance
• 6 What is a common application or real-world example related to 'Human Health and Disease'? medium MCQ Real World Application
• 7 What key takeaway should students retain after completing 'Human Health and Disease'? medium MCQ Chapter Summary & Takeaway
• 8 Discuss the mechanism of action of antiretroviral therapy (ART) in HIV infection and explain why a combination of drugs (HAART) is preferred over a single drug regimen. hard 5 marks Mechanism of ART and rationale for HAART
• 9 Which of the following is the primary lymphoid organ where B‑lymphocytes mature? easy MCQ 1 mark Site of B‑cell maturation
• 10 Both parents are heterozygous for the blood group allele AO (i.e., genotype AO). What is the probability that their child will have blood group O? Express your answer as a fraction. hard 4 marks Mendelian inheritance of blood groups
• 11 Explain how herd immunity helps to control the spread of measles in a population. medium 3 marks Herd immunity principle
• 12 In a community of 200 000 people, 120 000 are vaccinated against measles. If the basic reproduction number (R0) of measles is 15, what percentage of the population needs to be immune to achieve herd immunity? hard 4 marks Herd immunity calculation
• 13 Explain why a live attenuated measles vaccine elicits stronger immunity than an inactivated vaccine. medium 3 marks Vaccine immunology
• 14 A 60‑year‑old woman with cystitis is treated with amoxicillin but symptoms persist. Urine culture shows β‑lactamase–producing Klebsiella pneumoniae. Suggest a second‑line oral antibiotic and justify the choice based on mechanism of action and resistance profile. hard 4 marks Antibiotic resistance management
• 15 Which class of antiretroviral drugs blocks the cleavage of the HIV Gag‑Pol polyprotein? easy MCQ 2 marks HAART drug class function
• 16 Explain how Staphylococcus aureus becomes resistant to penicillin by altering its penicillin‑binding proteins (PBPs). medium 2 marks Antibiotic resistance via target modification
• 17 Which of the following is the primary lymphoid organ where T‑lymphocytes mature? easy MCQ 1 mark Primary lymphoid organ for T cells
• 18 A 45‑year‑old man has been diagnosed with type 2 diabetes mellitus and is prescribed metformin. (a) Explain the biochemical mechanism by which metformin lowers blood glucose. (b) Recommend two lifestyle modifications that should accompany the drug therapy. (c) Mention one common side effect of metformin and how it can be managed. hard 5 marks Metformin action and diabetes management
• 19 In a population of 500,000 people, a disease has a basic reproduction number (R₀) of 12. If 80% of the population has been vaccinated with a vaccine that is 85% effective, what additional percentage of the population must be immune (through natural infection or other means) to achieve herd immunity? medium 3 marks Herd immunity calculation with vaccine efficacy
• 20 Which organ is the primary site of maturation of B‑lymphocytes? easy MCQ 1 mark Primary lymphoid organ for B‑cell maturation
• 21 A 55‑year‑old male with type 2 diabetes is started on a sulfonylurea drug. (a) Explain how sulfonylureas stimulate insulin release from pancreatic β‑cells. (b) Mention one common adverse effect of sulfonylureas and a dietary recommendation to manage it. medium 2 marks Mechanism and side‑effects of sulfonylureas
• 22 A Gram‑negative bacillus isolated from a urinary tract infection shows resistance to third‑generation cephalosporins due to production of extended‑spectrum β‑lactamase (ESBL). (a) Explain the biochemical mechanism by which ESBL confers resistance to these antibiotics. (b) Propose an oral antibiotic that would be effective against this organism and justify your choice based on its mechanism and the resistance profile. hard 4 marks Mechanism of ESBL resistance and treatment choice
• 23 In a city of 600 000 people, a disease has R₀ = 10. A vaccine with 80 % efficacy is given to 70 % of the population. Assuming random mixing, calculate the additional percentage of the population that must already be immune (through prior infection or other measures) to achieve herd immunity. hard 3 marks Herd immunity calculation with vaccine efficacy
• 24 A 70‑year‑old woman has been diagnosed with hypertension. Explain how calcium channel blockers help reduce blood pressure and give an example of a commonly used dihydropyridine calcium channel blocker in India. easy 2 marks CCB action on vascular smooth muscle
• 25 Which enzyme in the human liver is directly inhibited by metformin, thereby reducing hepatic gluconeogenesis? easy MCQ 1 mark Metformin target enzyme
• 26 In a city of 400 000 people, a disease has a basic reproduction number R_0 = 8. A vaccine that is 90 % effective is given to 65 % of the population. Assuming random mixing, calculate the additional percentage of the population that must already be immune (through prior infection or other measures) to achieve herd immunity. medium 3 marks Herd immunity calculation with vaccine efficacy
• 27 Explain the mechanism of action of omeprazole in the treatment of peptic ulcer disease and why it is preferred over H2‑receptor antagonists for long‑term ulcer healing. hard 5 marks Proton‑pump inhibitor mechanism
• 28 A Klebsiella pneumoniae strain isolated from a urinary tract infection carries the plasmid‑mediated mcr-1 gene. (a) Explain how the mcr-1 gene confers resistance to colistin. (b) Suggest an alternative oral antibiotic that would likely be effective against this strain and justify your choice. hard 5 marks Plasmid‑mediated colistin resistance
• 29 In a city of 250,000 people, a measles outbreak has a basic reproduction number R_0=18. A vaccine with 95 % efficacy is given to 85 % of the population. Assuming random mixing, calculate the additional percentage of the population that must already be immune (through prior infection or other measures) to achieve herd immunity. medium 4 marks Herd immunity calculation
• 30 A urinary isolate of *Enterococcus faecalis* carries a plasmid‑mediated *vanA* gene. (a) Describe how the *vanA* gene confers resistance to vancomycin. (b) Recommend an oral antibiotic that would likely be effective against this strain and justify your choice based on its mechanism of action and the resistance profile. hard 5 marks Vancomycin resistance via *vanA* and alternative therapy
• 31 Which of the following is the primary lymphoid organ where B‑lymphocytes mature? easy MCQ 1 mark Primary lymphoid organ for B cells
• 32 Explain the mechanism by which omeprazole promotes healing of peptic ulcers and state why it is preferred over H2‑receptor antagonists for long‑term therapy. medium 3 marks Proton pump inhibitor action in ulcer healing
• 33 In a town of 300 000 residents, a viral disease has a basic reproduction number R_0 = 12. A vaccine that is 80 % effective has been administered to 60 % of the population. Assuming random mixing, calculate the additional percentage of people that must already be immune (through prior infection or other means) to achieve herd immunity. hard 4 marks Herd immunity calculation with vaccine efficacy
• 34 Explain how calcium channel blockers reduce blood pressure and name a commonly used dihydropyridine calcium channel blocker in India. easy 2 marks Calcium channel blocker action in hypertension
• 35 In a population of 200,000, a contagious disease has basic reproduction number R_0 = 6. A vaccine with 70 % efficacy is given to 80 % of the population. Assuming random mixing, calculate the additional percentage of the population that must already be immune (through prior infection or other means) to achieve herd immunity. medium 3 marks Herd immunity calculation
• 36 A urinary isolate of *Escherichia coli* carries the plasmid‑mediated *mcr‑1* gene. (a) Explain how the *mcr‑1* gene confers resistance to colistin. (b) Suggest an alternative oral antibiotic that would likely be effective against this strain and justify your choice based on its mechanism of action and the resistance profile. hard 5 marks Plasmid‑mediated colistin resistance mechanism
• 37 Explain the mechanism of action of HIV integrase inhibitors and why combination antiretroviral therapy (HAART) is required for effective treatment of HIV infection. hard 5 marks HIV integrase inhibitor mechanism and HAART rationale