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A Level Biology: Infectious diseases MCQs — Biology

19 multiple-choice questions on A Level Biology: Infectious diseases from Biology, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. Penicillin is most effective against bacteria that are

  1. viruses
  2. dormant
  3. fungi
  4. growing and making new cell wall

Answer: D) growing and making new cell wall

Explanation: It targets wall synthesis. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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2. Insecticide-treated bed nets reduce malaria by

  1. vaccinating people
  2. preventing mosquitoes biting at night
  3. killing Plasmodium in the blood
  4. cleaning water

Answer: B) preventing mosquitoes biting at night

Explanation: They block the vector. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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3. Which practice reduces the development of antibiotic resistance?

  1. Completing the full course of antibiotics
  2. Using antibiotics for colds
  3. Stopping the course when feeling better
  4. Giving antibiotics to healthy farm animals

Answer: A) Completing the full course of antibiotics

Explanation: Incomplete courses select for resistance. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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4. HIV can be transmitted by

  1. drinking contaminated water
  2. mosquito bites
  3. coughing
  4. sharing hypodermic needles

Answer: D) sharing hypodermic needles

Explanation: Blood and body fluids transmit HIV. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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5. Antibiotic resistance spreads in a population of bacteria because

  1. all bacteria die
  2. antibiotics cause bacteria to become resistant deliberately
  3. resistant bacteria survive and reproduce when the antibiotic is used
  4. viruses carry resistance

Answer: C) resistant bacteria survive and reproduce when the antibiotic is used

Explanation: Selection favours resistant mutants. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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6. Which measure helps control cholera?

  1. BCG vaccination
  2. Wearing condoms
  3. Using bed nets
  4. Treating sewage and chlorinating water

Answer: D) Treating sewage and chlorinating water

Explanation: Cholera is waterborne. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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7. Which pathogen causes cholera?

  1. Vibrio cholerae
  2. Mycobacterium tuberculosis
  3. HIV
  4. Plasmodium falciparum

Answer: A) Vibrio cholerae

Explanation: Cholera is caused by a bacterium, Vibrio cholerae. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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8. Why is it difficult to develop a vaccine for malaria?

  1. it is a bacterium with a cell wall
  2. there is no immune response at all
  3. it is a virus
  4. Plasmodium changes its antigens and lives inside cells

Answer: D) Plasmodium changes its antigens and lives inside cells

Explanation: Antigenic variation and intracellular stages. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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9. Malaria is caused by a

  1. bacterium
  2. protoctist
  3. fungus
  4. virus

Answer: B) protoctist

Explanation: Plasmodium is a protoctist. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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10. A social factor that increases the spread of TB is

  1. overcrowded, poorly ventilated housing
  2. clean water supply
  3. pasteurised milk
  4. vaccination

Answer: A) overcrowded, poorly ventilated housing

Explanation: Droplets spread easily in crowded homes. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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11. HIV is described as a

  1. prion
  2. bacterium
  3. protoctist
  4. virus

Answer: D) virus

Explanation: Human immunodeficiency virus. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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12. Mycobacterium bovis can be transmitted to humans through

  1. mosquito bites
  2. contaminated water only
  3. shared needles
  4. unpasteurised milk

Answer: D) unpasteurised milk

Explanation: Infected cattle products spread M. bovis. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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13. Penicillin kills bacteria by

  1. breaking down DNA
  2. blocking ribosomes in humans
  3. preventing cross-links forming in the cell wall, so cells burst
  4. destroying viruses

Answer: C) preventing cross-links forming in the cell wall, so cells burst

Explanation: Weak walls lead to osmotic lysis. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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14. Resistance genes can be passed between bacteria on

  1. plasmids
  2. ribosomes
  3. capsids
  4. mitochondria

Answer: A) plasmids

Explanation: Plasmids transfer genes horizontally. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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15. Which is a vector?

  1. Plasmodium
  2. Vibrio cholerae
  3. Anopheles mosquito
  4. HIV

Answer: C) Anopheles mosquito

Explanation: The mosquito carries the pathogen. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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16. A consequence of antibiotic resistance is that

  1. bacteria stop reproducing
  2. infections become more difficult to treat
  3. all infections become viral
  4. vaccines stop working

Answer: B) infections become more difficult to treat

Explanation: Resistant infections are harder to treat. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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17. Antibiotics do not affect viruses because viruses

  1. have no cell walls or metabolism of their own
  2. have thick cell walls
  3. have plasmids
  4. are too large

Answer: A) have no cell walls or metabolism of their own

Explanation: Antibiotic targets are absent in viruses. AS & A Level Biology · Topic 10 Infectious Diseases · 10.2 Antibiotics

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18. TB is mainly transmitted by

  1. insect stings
  2. mosquito bites
  3. airborne droplets
  4. contaminated water

Answer: C) airborne droplets

Explanation: Coughing spreads Mycobacterium. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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19. TB treatment uses several antibiotics for at least six months to

  1. reduce the chance of resistance developing
  2. reduce the number of mosquitoes
  3. kill viruses
  4. make the vaccine work

Answer: A) reduce the chance of resistance developing

Explanation: Long multi-drug courses prevent resistance. AS & A Level Biology · Topic 10 Infectious Diseases · 10.1 Infectious diseases

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