Human defence systems and vaccination – GCSE Biology exam questions with mark scheme

1Grade 4–55 marks

(a) Explain how the trachea and bronchi help to stop pathogens entering the lungs. [2]

(b) Give three ways that white blood cells help to defend the body against pathogens. [3]

(a) (goblet cells produce) mucus which traps pathogens(1)
(a) cilia move / waft the mucus up (to the throat where it is swallowed)(1)
(b) phagocytosis / ingesting (engulfing) pathogens(1)
(b) producing antibodies(1)
(b) producing antitoxins (to neutralise toxins)(1)
Answer: (a) mucus traps pathogens; cilia move mucus away (b) phagocytosis; antibodies; antitoxins
Examiner tip: Cilia do not trap pathogens — mucus traps them and cilia MOVE the mucus.

2Grade 6–74 marks

Explain how vaccination can prevent a person from becoming ill with measles. [4]

a small quantity of dead or inactive (form of the) pathogen / virus is injected (allow weakened / harmless form; allow antigens of the virus)(1)
this stimulates white blood cells / lymphocytes to produce (specific) antibodies(1)
if the same pathogen re-enters the body, white blood cells respond rapidly to produce the correct antibodies (in large numbers) (allow memory cells respond quickly)(1)
so the pathogen is destroyed before it can cause symptoms / illness(1)
Answer: Dead/inactive virus injected → white blood cells make antibodies → rapid antibody production on re-infection → virus destroyed before symptoms.
Examiner tip: Vaccines contain dead or inactive pathogens (antigens), NOT antibodies — this is the most common lost mark.

3Grade 1–3Foundation4 marks

The body has defences that stop pathogens getting in.

(a) Draw one line from each part of the body to how it helps to stop pathogens. [3]

Part of the body	How it helps to stop pathogens
Skin	Contains hairs and mucus that trap particles
Stomach	Pumps blood around the body
Nose	Acts as a barrier that covers the body
	Produces acid that kills pathogens
	Produces antibodies

(b) Pathogens that get past these defences can be destroyed in the blood.

Which type of blood cell destroys pathogens?

Tick (✓) one box. [1]

☐ Platelet
☐ Red blood cell
☐ White blood cell

(a) Skin → acts as a barrier that covers the body (more than one line from a part of the body: no mark for that part)(1)
(a) Stomach → produces acid that kills pathogens(1)
(a) Nose → contains hairs and mucus that trap particles(1)
(b) white blood cell(1)
Answer: (a) Skin – barrier; Stomach – acid that kills pathogens; Nose – hairs and mucus trap particles. (b) White blood cell
Examiner tip: Stomach acid KILLS pathogens; it does not just 'digest food' – and antibodies are made by white blood cells, not by any of these organs.

4Grade 1–3Foundation4 marks

The diagram shows what happens when a white blood cell meets a bacterium. Stages A, B and C happen in order.

(a) Name the process shown in the diagram. [1]

(b) Describe what happens to the bacterium at stage B and at stage C. [2]

Name the substance that white blood cells produce to counteract toxins. [1]

(a) phagocytosis (allow phonetic spelling, e.g. 'fagocytosis'; do not accept 'photosynthesis')(1)
(b) stage B: the bacterium is engulfed / surrounded / taken in by the white blood cell (allow ingested; allow 'eaten')(1)
(b) stage C: the bacterium is digested / broken down / destroyed (by enzymes) (allow killed)(1)
(c) antitoxin(s) (do not accept antibodies; do not accept antibiotics)(1)
Answer: (a) Phagocytosis (b) B: bacterium engulfed by the white blood cell; C: bacterium digested / destroyed (c) Antitoxins
Examiner tip: Antitoxins neutralise toxins; antibodies target the pathogen itself, and antibiotics are medicines – students often mix up all three words.

5Grade 4–56 marks

Cigarette smoke contains tar. Tar damages the cilia on cells lining the trachea and bronchi so that they stop moving.

Scientists recorded the number of chest infections that six smokers had in one year.

Smoker	1	2	3	4	5	6
Number of chest infections in one year	3	5	2	4	3	1

(a) Calculate the mean number of chest infections per smoker. [1]

(b) The mean number of chest infections for a group of non-smokers was 1.2 per year.

Calculate how many times more chest infections the smokers had than the non-smokers. [1]

(d) A student said: ‘This study proves that smoking causes chest infections.’

Give one reason why the student’s conclusion is not valid. [1]

(a) 3 (allow 3.0)(1)
(b) 2.5 (times) (allow ecf from (a): their mean ÷ 1.2)(1)
(c) (normally) mucus traps pathogens / bacteria / viruses (in the airways)(1)
(c) (normally) cilia move / waft the mucus (and trapped pathogens) up and out of the airways / to the throat (to be swallowed)(1)
(c) damaged / stopped cilia cannot remove the mucus, so mucus containing pathogens stays / builds up and pathogens reach the lungs / multiply (do not accept 'cilia trap pathogens')(1)
(d) sample is (too) small / only six smokers (allow: other factors not controlled, e.g. age / health / exposure to other people with infections; allow: no repeat / only one year) (ignore 'not fair' unqualified)(1)
Answer: (a) 3 (b) 2.5 times (c) Mucus traps pathogens; cilia normally move mucus out of the airways; damaged cilia cannot, so pathogens stay and reach the lungs. (d) Sample of only six smokers is too small (or other variables not controlled).
Examiner tip: Mucus traps pathogens and cilia MOVE the mucus – saying 'cilia trap pathogens' loses a mark every year.

6Grade 4–57 marks

A secondary school has 1450 pupils. 1247 of the pupils have been vaccinated against measles.

(a) Calculate the percentage of pupils who have been vaccinated. [2]

(b) Doctors say that at least 95% of people in a population need to be vaccinated to stop measles spreading.

Calculate how many more pupils need to be vaccinated for the school to reach 95%. [2]

(c) Explain how vaccinating a large proportion of the pupils also protects pupils who have not been vaccinated. [2]

(d) Suggest one reason why a pupil may not have been vaccinated. [1]

(a) 1247 ÷ 1450 (× 100)(1)
(a) 86 (%) (allow 86.0)(1)
(b) 0.95 × 1450 = 1377.5, so 1378 pupils needed (allow 1377.5 seen)(1)
(b) 131 (allow 130.5 for 1 mark only; 1378 − 1247 = 131)(1)
(c) fewer pupils can be infected / carry the virus, so there are fewer sources of infection (in the school)(1)
(c) so an unvaccinated pupil is less likely to come into contact with an infected person / the virus is less likely to spread (to them) (allow herd immunity / herd effect explained; 'herd immunity' alone = 0)(1)
(d) any sensible reason, e.g. a medical condition / weakened immune system / allergic to the vaccine; parents chose not to / did not consent; missed the appointment / was absent; joined from another country (ignore 'scared of needles' unqualified)(1)
Answer: (a) 86% (b) 131 more pupils (c) Fewer pupils can catch and pass on measles, so unvaccinated pupils are less likely to meet an infected person. (d) e.g. a medical condition that means they cannot be vaccinated.
Examiner tip: You cannot vaccinate half a pupil: 95% of 1450 is 1377.5, so round UP to 1378 before subtracting.

7Grade 8–9Higher4 marks

Influenza (flu) is caused by a virus. The proteins on the surface of the flu virus are called antigens. The antigens change slightly from one year to the next, so a new flu vaccine is made every year.

(a) A person had the flu vaccine last year. This year they caught the new strain of flu and became ill.

Explain why last year’s vaccine did not protect them. [3]

(b) Health care workers in hospitals are offered the flu vaccine every year.

Suggest one reason why. [1]

(a) antibodies are specific to (the antigens on) one pathogen / strain (allow antibodies only fit / bind to one shape of antigen)(1)
(a) the new strain has different antigens, so last year’s antibodies / white blood cells do not recognise it / cannot bind to it(1)
(a) so there is no rapid (secondary) antibody response; antibodies are made too slowly and the virus reproduces / damages cells before it is destroyed (causing symptoms)(1)
(b) any one from: they are in contact with many ill people, so are more likely to be exposed; so they do not pass flu on to patients who are already ill / vulnerable; so they stay well enough to keep working (ignore 'to protect them' unqualified)(1)
Answer: (a) Antibodies are specific; the new strain has different antigens, so the person’s white blood cells do not recognise it and cannot make antibodies quickly; the virus multiplies and causes illness. (b) They meet many infected people / could pass flu to vulnerable patients.
Examiner tip: Say WHY the protection fails: antibodies are specific to one antigen shape – 'the virus has mutated' alone does not score.

8Grade 8–9Higher4 marks

Tetanus is caused by a bacterium that enters the body through deep cuts. The bacterium releases a toxin that damages nerves.

A farmer who has never been vaccinated against tetanus gets a deep cut. A doctor gives the farmer two injections:

an injection of antitoxin, taken from a person who is immune to tetanus
the tetanus vaccine, which contains an inactive form of the toxin.

Explain why the doctor gives the farmer both injections. [4]

the (injected) antitoxin neutralises / counteracts the toxin straight away (allow antibodies)(1)
(because) the farmer has never been exposed to the toxin, so his own white blood cells would take too long to produce antitoxins (and the toxin would damage nerves first)(1)
the injected antitoxin does not last / is broken down, (so it gives no long-term protection) because it was not made by the farmer’s own white blood cells(1)
the vaccine stimulates the farmer’s white blood cells to produce antitoxins / antibodies, so in a future infection they are produced rapidly (giving long-term protection) (do not accept 'the vaccine contains antitoxins / antibodies')(1)
Answer: The antitoxin neutralises the toxin immediately, because the farmer’s own white blood cells would respond too slowly the first time; but injected antitoxin does not last. The vaccine makes his own white blood cells produce antitoxins, so they respond rapidly in any future infection.
Examiner tip: Keep the two injections apart: antitoxin = immediate but short-term; vaccine = no immediate help but long-term, rapid response next time.

9Grade 6–76 marks

A student said:

‘Our bodies already have lots of defences against pathogens, so people do not need to be vaccinated.’

Evaluate the student’s statement.

Use your knowledge of the body’s defence systems and of vaccination. [6]

For: skin acts as a barrier to pathogens(1)
For: nose – hairs and mucus trap particles; trachea and bronchi – mucus traps pathogens and cilia move it out of the airways(1)
For: stomach acid kills pathogens in food and drink(1)
For: white blood cells engulf pathogens by phagocytosis, produce antibodies and produce antitoxins(1)
Against: pathogens can still get past non-specific defences, e.g. through cuts or by being inhaled(1)
Against: the first time a pathogen enters, white blood cells take time to produce the right antibodies, so the pathogen can reproduce and cause illness (or death) first(1)
Against: a vaccine (small amount of dead / inactive pathogen) stimulates white blood cells to produce antibodies without causing illness(1)
Against: if the same pathogen enters later, antibodies are produced rapidly, so the person does not become ill(1)
Against: vaccinating a large proportion of the population reduces spread (herd effect), protecting people who cannot be vaccinated(1)
Conclusion: the statement is not correct overall – natural defences help, but vaccination is needed to prevent serious illness and reduce spread(1)

Level	Marks	What it looks like
Level 3	5–6	Gives a balanced evaluation: describes several of the body’s defences AND explains why they are not enough, linking slow antibody production on first infection to illness and the rapid response after vaccination (and/or the herd effect). Reaches a clear conclusion that is supported by the reasoning.
Level 2	3–4	Describes some defences and gives at least one relevant reason why vaccination is still useful, but the explanation is incomplete or one side is weak. A conclusion may be given but is not fully supported.
Level 1	1–2	Makes simple relevant statements, e.g. names some defences or states that vaccines make antibodies. Little or no attempt to weigh up the statement.
No marks	0	No relevant content.

Answer: Natural defences (skin, nose, mucus and cilia, stomach acid, white blood cells) do stop many pathogens, but on first infection antibodies are produced too slowly to prevent illness. Vaccination gives a rapid response on later infection and reduces spread through the herd effect, so the statement is wrong.
Examiner tip: ‘Evaluate’ needs both sides AND a conclusion – an answer that only lists defences cannot get above Level 2.

10Grade 6–7Higher6 marks

A person was vaccinated against a disease on day 0. On day 50 the same person was exposed to the live pathogen that causes the disease.

The graph shows the concentration of antibodies against this pathogen in the person’s blood.

(a) How many days after vaccination was the antibody concentration at its highest before day 50? [1]

(b) Calculate the mean rate of increase in antibody concentration between day 50 and day 55.

Give the unit. [2]

(d) The vaccine contained a dead form of the pathogen.

Explain why the vaccine did not make the person ill. [1]

(a) 14 (days) (allow 13–15)(1)
(b) (120 − 10) ÷ 5 (allow readings of 118–122 at day 55 and 8–12 at day 50)(1)
(b) 22 arbitrary units per day (allow 21–23; unit required for this mark: allow AU/day, units/day)(1)
(c) any two from (1 mark each): antibodies produced faster / sooner / with no delay after exposure (allow rises immediately at day 50 compared with a delay of about 5 days after vaccination); a (much) higher concentration of antibodies is produced (allow peak about 130 compared with 20 / about 6.5 times higher); concentration stays high for longer (allow still above 110 at day 80, 20 days after the peak, whereas after vaccination it had about halved 20 days after the peak; allow falls by a smaller proportion; do not accept ‘falls more slowly’ unqualified, as the actual fall after day 60 is larger).(1)
(c) a second, different difference from the list above (allow numbers quoted from the graph to support each point)(1)
(d) dead pathogen cannot reproduce (in the body) / cannot damage cells / cannot release toxins (allow inactive pathogen is harmless) (ignore 'it is weak')(1)
Answer: (a) 14 days (b) 22 arbitrary units per day (c) Faster response; much higher antibody concentration (or lasts longer) (d) Dead pathogen cannot reproduce or damage cells.
Examiner tip: In rate questions the unit carries a mark – write 'arbitrary units per day', not just the number.

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