AQA GCSE Combined Science: Trilogy · 4.3

Infection and response

Revision questions with answers for 4.3 Infection and response in AQA GCSE Combined Science: Trilogy (spec 8464). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All questions and answers

Question 1 · Spec 4.3.1.1
What is a pathogen?
Answer:
A microorganism that causes infectious disease.
Question 2 · Spec 4.3.1.1
Name the four pathogen groups in this unit.
Answer:
Bacteria, viruses, fungi and protists.
Question 3 · Spec 4.3.1.1
Name three ways pathogens can spread.
Answer:
Through air, water and direct contact between organisms.
Question 4 · Spec 4.3.1.1
How can bacteria make an infected person ill?
Answer:
They can reproduce rapidly and release toxins that damage tissues.
Question 5 · Spec 4.3.1.1
How do viruses damage their host?
Answer:
They reproduce inside host cells, damaging or destroying those cells.
Question 6 · Spec 4.3.1.1
How can waterborne disease transmission be reduced?
Answer:
Treat drinking water and sewage, and prevent drinking-water supplies becoming contaminated.
Question 7 · Spec 4.3.1.1
How do handwashing and disinfecting surfaces reduce disease spread?
Answer:
They remove or kill pathogens, reducing transfer by direct contact or contaminated objects.
Question 8 · Spec 4.3.1.1
Why can isolating an infectious person reduce transmission?
Answer:
It reduces opportunities for the pathogen to pass to susceptible people.
Question 9 · Spec 4.3.1.2
What causes measles, and what are its main symptoms?
Answer:
A virus causes measles. Typical symptoms are fever and a red skin rash.
Question 10 · Spec 4.3.1.2
How is measles transmitted?
Answer:
By inhaling droplets released when an infected person coughs or sneezes.
Question 11 · Spec 4.3.1.2
Why are children vaccinated against measles?
Answer:
Measles can cause serious, sometimes fatal complications; vaccination reduces illness and transmission.
Question 12 · Spec 4.3.1.2
What can happen early in HIV infection?
Answer:
A flu-like illness may occur before substantial damage to the immune system develops.
Question 13 · Spec 4.3.1.2
How can HIV infection be controlled?
Answer:
Antiretroviral drugs reduce viral replication and help prevent damage to immune cells.
Question 14 · Spec 4.3.1.2
How is HIV transmitted?
Answer:
Through sexual contact or exchange of infected body fluids, for example blood on shared needles.
Question 15 · Spec 4.3.1.2
Why does untreated HIV increase the risk of other infections?
Answer:
It damages immune cells. In late-stage infection, AIDS, the immune system cannot effectively deal with other infections or some cancers.
Question 16 · Spec 4.3.1.2
What is the visible symptom of tobacco mosaic virus?
Answer:
A distinctive mosaic pattern of discolouration on leaves.
Question 17 · Spec 4.3.1.2
Why does tobacco mosaic virus reduce plant growth?
Answer:
Leaf discolouration reduces photosynthesis, so less glucose is available for respiration and building new biomass.
Question 18 · Spec 4.3.1.3
How is salmonella food poisoning transmitted?
Answer:
By ingesting bacteria in contaminated food, including food prepared under unhygienic conditions.
Question 19 · Spec 4.3.1.3
What symptoms can salmonella cause?
Answer:
Fever, abdominal cramps, vomiting and diarrhoea, caused by the bacteria and their toxins.
Question 20 · Spec 4.3.1.3
How does vaccinating poultry help control salmonella?
Answer:
It reduces infection in poultry and the chance of bacteria reaching humans through contaminated food.
Question 21 · Spec 4.3.1.3
What causes gonorrhoea, and what are possible symptoms?
Answer:
A bacterium causes it. Symptoms include pain when urinating and a thick yellow or green discharge.
Question 22 · Spec 4.3.1.3
How is gonorrhoea spread?
Answer:
By sexual contact with an infected person.
Question 23 · Spec 4.3.1.3
How can gonorrhoea transmission be reduced?
Answer:
Use barrier contraception such as condoms and treat infections with an effective antibiotic.
Question 24 · Spec 4.3.1.3
Why is penicillin no longer effective against many gonorrhoea strains?
Answer:
Many strains have evolved resistance, so that antibiotic no longer kills them effectively.
Question 25 · Spec 4.3.1.4
What causes rose black spot, and what are its symptoms?
Answer:
A fungus causes purple or black leaf spots; leaves may yellow and drop early.
Question 26 · Spec 4.3.1.4
How does rose black spot spread?
Answer:
Fungal spores are spread through the environment by water or wind.
Question 27 · Spec 4.3.1.4
How can rose black spot be controlled?
Answer:
Use a suitable fungicide and remove and destroy affected leaves.
Question 28 · Spec 4.3.1.4
Why does early leaf loss reduce a rose's growth?
Answer:
It reduces the surface available for photosynthesis and therefore the glucose produced for growth.
Question 29 · Spec 4.3.1.5
Which pathogen group causes malaria, and what is a typical symptom?
Answer:
A protist causes malaria, producing recurrent fever; severe infection can be fatal.
Question 30 · Spec 4.3.1.5
Why is a mosquito described as a malaria vector?
Answer:
It carries and transmits the protist between human hosts; the mosquito itself is not the pathogen.
Question 31 · Spec 4.3.1.5
Give two ways to reduce malaria transmission.
Answer:
Prevent mosquitoes breeding and use mosquito nets to reduce bites.
Question 32 · Spec 4.3.1.6
How does the skin defend against pathogens?
Answer:
It provides a physical barrier; clotting seals damaged areas and helps prevent pathogen entry.
Question 33 · Spec 4.3.1.6
How do the nose's hairs and mucus help defend the body?
Answer:
They trap particles and pathogens before they reach deeper airways.
Question 34 · Spec 4.3.1.6
How do the trachea and bronchi remove pathogens?
Answer:
Mucus traps pathogens, and cilia move the mucus towards the throat to be swallowed.
Question 35 · Spec 4.3.1.6
How does the stomach provide a non-specific defence?
Answer:
Its hydrochloric acid kills many swallowed pathogens.
Question 36 · Spec 4.3.1.6
Name three ways white blood cells defend against pathogens.
Answer:
Phagocytosis, antibody production and antitoxin production.
Question 37 · Spec 4.3.1.6
What happens during phagocytosis?
Answer:
A white blood cell engulfs a pathogen and digests it.
Question 38 · Spec 4.3.1.6
Why are antibodies specific?
Answer:
An antibody has a shape complementary to a particular antigen, allowing it to bind to that antigen.
Question 39 · Spec 4.3.1.6
What do antitoxins do?
Answer:
They neutralise toxins released by pathogens.
Question 40 · Spec 4.3.1.7
How does vaccination help prevent illness on later exposure?
Answer:
Pathogen antigens stimulate an immune response. On re-exposure, white blood cells produce the correct antibodies much faster.
Question 41 · Spec 4.3.1.7
Why can vaccinating a large proportion of a population protect others?
Answer:
Fewer susceptible hosts reduce transmission, making it less likely that the pathogen reaches unvaccinated people.
Question 42 · Spec 4.3.1.8
What are antibiotics used for?
Answer:
Treating bacterial infections by killing bacteria or stopping their growth; an effective antibiotic must match the bacteria involved.
Question 43 · Spec 4.3.1.8
Why do antibiotics not cure viral infections?
Answer:
Viruses reproduce inside host cells and lack the bacterial structures or processes targeted by antibiotics.
Question 44 · Spec 4.3.1.8
How does a painkiller differ from an antibiotic?
Answer:
A painkiller relieves symptoms such as pain but does not kill the pathogen; antibiotics act against bacteria.
Question 45 · Spec 4.3.1.9
Match digitalis and aspirin to their original plant sources.
Answer:
Digitalis originated from foxgloves; aspirin originated from chemicals found in willow.
Question 46 · Spec 4.3.1.9
Who discovered penicillin, and what organism produced it?
Answer:
Alexander Fleming discovered penicillin, produced by the Penicillium mould.
Question 47 · Spec 4.3.1.9
What do toxicity, efficacy and dose mean in drug testing?
Answer:
Toxicity: harmful effects; efficacy: how well the drug works; dose: amount given, with trials seeking an effective, sufficiently safe dose.
Question 48 · Spec 4.3.1.9
What is preclinical testing?
Answer:
Laboratory testing on cells, tissues and live animals before trials in humans.
Question 49 · Spec 4.3.1.9
How do clinical trials progress?
Answer:
They begin with very low doses in healthy volunteers to assess safety, then test efficacy and suitable doses in patients.
Question 50 · Spec 4.3.1.9
How do placebo, double-blind trials and peer review improve evidence?
Answer:
Placebos allow comparison; neither participants nor investigators know treatment allocation, reducing bias; other scientists scrutinise the findings through peer review.

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