2025 OCR GCSE Gateway Science - Biology A - J247 Practice Paper with Answers

A vaccine contains a harmless form of the pathogen's antigens, so memory lymphocytes are produced. On re-infection they respond quickly and make the specific antibody in large amounts, so the bacterium is destroyed before symptoms develop. Vaccines do not contain antibiotics (B), phagocytes engulf pathogens rather than make antibodies (C), and platelets are involved in clotting (D).

A (1 mark, AO1/AO2).
B, C and D are incorrect distractors: B vaccines do not contain antibiotics; C phagocytes do not make antibodies; D platelets clot blood. Award 1 mark for A only; no marks if more than one box is selected.

Biuret reagent tests for protein. A positive result is a colour change from blue to purple (lilac). Brick-red is the Benedict's test result for reducing sugars, and blue-black is the iodine result for starch.

A (1 mark, AO1).
Distractors: B mixes protein with the Benedict's colour; C and D name the wrong molecule for the colour change. Award 1 mark for A only.

The impulse starts at the receptor, travels along the sensory neurone to the relay neurone in the central nervous system, then along the motor neurone to the effector (a muscle), which pulls the hand away.

B (1 mark, AO1).
A, C and D have neurones or structures in the wrong order. Award 1 mark for B only.

At high temperatures the bonds holding the enzyme in shape break and the enzyme becomes denatured. The active site changes shape so the substrate no longer fits, and the rate falls. Molecules move faster, not slower, at higher temperature.

B (1 mark, AO1/AO2).
C is wrong because particles move faster when heated; A and D are not caused by temperature. Award 1 mark for B only.

LH from the pituitary gland stimulates ovulation. FSH causes follicle development and oestrogen release. Oestrogen and progesterone are made by the ovary, not the pituitary gland.

C (1 mark, AO1).
A and B are ovarian hormones; D stimulates egg maturation, not release. Award 1 mark for C only.

Carbon dioxide is a reactant in photosynthesis. When its concentration is low it limits the rate, so adding more allows faster photosynthesis, more glucose and biomass, and a higher yield.

D (1 mark, AO2).
A, B and C describe effects that carbon dioxide does not have. Award 1 mark for D only.

Both parents are Ff. Gametes are F or f. Offspring: FF, Ff, Ff, ff, so 1 in 4 is ff. The probability is 1/4 = 0.25.

B (1 mark, AO2).
C is the probability of being a carrier; D is the probability of having at least one dominant allele. Award 1 mark for B only.

Surface area = 6 × 2 × 2 = 24 cm². Volume = 2 × 2 × 2 = 8 cm³. Ratio = 24 : 8 = 3 : 1.

B (1 mark, AO2).
Method: surface area 24 cm² and volume 8 cm³, ratio 3 : 1. C results from using one face (4) or 6 faces without dividing correctly; D is not derived from valid working. Award 1 mark for B only.

A vaccine contains a weakened or inactive form of the pathogen (antigens). This triggers lymphocytes to make specific antibodies and memory cells, so a faster response occurs on later infection. Antibiotics do not work on viruses (A), vaccines do not supply ready-made antibodies (C), and phagocytes are non-specific (D).

1 mark (AO1) for B only. Do not allow more than one letter. A: antibiotics do not kill viruses. C: describes passive immunity. D: not specific to measles.

\( \text{actual size} = \dfrac{\text{image size}}{\text{magnification}} = \dfrac{36}{400} = 0.09\ \text{mm} \).

1 mark (AO2) for B only. Method: image size ÷ magnification. D results from multiplying instead of dividing.

The impulse starts at the receptor, travels along the sensory neurone to the relay neurone in the CNS, then along the motor neurone to the effector (muscle), which causes the hand to move.

1 mark (AO1) for C only.

Insulin is secreted by the pancreas when blood glucose is high. It causes cells (especially liver and muscle) to take up glucose, so blood glucose concentration falls.

1 mark (AO1) for A only.

High temperature breaks bonds holding the enzyme's protein structure, so the active site changes shape (denaturation). The substrate can no longer bind, so the reaction stops.

1 mark (AO1) for C only. Enzymes are not used up in reactions (B).

Both parents are \( Ff \). Offspring: \( FF, Ff, Ff, ff \). Only \( ff \) has the disorder, so the probability is \( \dfrac{1}{4} = 25\% \).

1 mark (AO2) for B only. C is the probability of being a carrier; D is the probability of not having the disorder.

When the rate levels off, light is no longer the limiting factor. Another factor, such as carbon dioxide concentration or temperature, is limiting. Increasing carbon dioxide concentration could therefore raise the rate. The other options would reduce or not affect the rate.

1 mark (AO3) for D only.

a(i) The pancreas detects the glucose rise and secretes insulin.
a(ii) Insulin acts on the liver (and muscle) cells, converting glucose to glycogen.
b Decrease = 8.6 − 6.2 = 2.4 mmol/dm\(^3\). Time = 60 − 30 = 30 minutes. Rate = \(\frac{2.4}{30}\) = 0.08 mmol/dm\(^3\) per minute.
c Insulin is a protein, so if swallowed it would be broken down by digestive enzymes and not absorbed intact into the blood.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| a(i) | pancreas | 1 | AO1 | DO NOT ALLOW islets/pancreatic cells alone if organ not named; ALLOW 'pancreas' with extra correct detail |
| a(ii) | liver | 1 | AO1 | ALLOW muscle(s) as an alternative; DO NOT ALLOW pancreas |
| b | Correct final answer 0.08 (mmol/dm\(^3\) per minute) = 2 marks. If answer incorrect: 8.6 − 6.2 = 2.4 (1 mark) OR \(\frac{2.4}{30}\) (1 mark) | 2 | AO2 | ALLOW 0.080. ALLOW ECF for one mark if a wrong time interval or subtraction is used consistently and the division is correct. Unit is given in the question; IGNORE missing unit |
| c | insulin is a protein (1) AND would be digested/broken down (by enzymes/protease) in the stomach/gut/digestive system (1) – both needed for the mark | 1 | AO1 | ALLOW 'would not be absorbed into blood intact'; IGNORE 'faster'/'more convenient' alone; IGNORE 'destroyed by acid' alone |

Total: 5 marks

(a)(i) The pancreas releases insulin.
(ii) After the rise in blood glucose, insulin is released and travels in the blood to target cells (liver and muscle). It makes them take up glucose and the liver converts glucose to glycogen, so blood glucose concentration falls.
(b) Decrease = 7.8 - 5.2 = 2.6 mmol/dm\(^3\). Time = 120 - 60 = 60 min. Rate = \(2.6 \div 60 = 0.04333...\) = 0.043 mmol/dm\(^3\) per minute (2 s.f.).
(c) Insulin is a protein, so if swallowed it would be digested by protease enzymes in the gut into amino acids and would not enter the blood as insulin. Injection puts it straight into the blood/tissue fluid.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| (a)(i) | pancreas | 1 | AO1 | DO NOT ALLOW pancrea/islets alone if organ is wrong; ALLOW 'pancreas (islet) cells' |
| (a)(ii) | any two from: insulin travels in the blood to liver/muscle (cells) (1); causes cells to take up glucose / glucose moves from blood into cells (1); glucose converted to glycogen (for storage) (1) | 2 | AO1 | ALLOW 'insulin converts glucose to glycogen'. IGNORE 'insulin breaks down glucose'. DO NOT ALLOW glucagon being released |
| (b) | correct answer 0.043 = 2 marks. Otherwise: 7.8 - 5.2 = 2.6 (1) and/or 2.6 / 60 (1) | 2 | AO2 | ALLOW 0.04 or 0.0433 for 1 mark only if working shown but not rounded to 2 s.f. (i.e. max 1 for unrounded 0.04333). Allow ECF for one mark if wrong subtraction is divided by 60. Unit given in question |
| (c) | (insulin is a) protein and would be digested / broken down (1); by protease (enzymes) in the stomach / gut / digestive system (1) (so would not be absorbed into the blood as insulin / would not work) | 2 | AO2 | ALLOW 'enzymes / acid would break it down' for 1 mark if protein not linked; ALLOW 'broken down into amino acids'. IGNORE 'less painful' / 'faster' unless linked to the digestion idea |

a(i) The pancreas releases insulin. (ii) The liver converts glucose to glycogen for storage.
b) Increase = 14.0 − 5.0 = 9.0 mmol/dm³. Percentage increase = \( \frac{9.0}{5.0} \times 100 = 180\% \).
c) The high blood glucose is detected by the pancreas, which secretes more insulin. Insulin causes liver (and muscle) cells to take up glucose and convert it to glycogen, so blood glucose concentration falls back towards normal.
d) Insulin is a protein, so it would be digested by protease enzymes in the stomach/small intestine before reaching the blood.

a(i) pancreas [1] (AO1). DO NOT ALLOW pituitary gland/adrenal gland.
a(ii) liver [1] (AO1). ALLOW muscles. IGNORE adipose tissue.
b) Correct final answer 180 (%) [2] (AO2). Method: (14.0 − 5.0) ÷ 5.0 × 100 [1]. ALLOW 9 ÷ 5 × 100 [1]. An answer of 280 (no subtraction) scores 0.
c) Any three from [3] (AO1 x2, AO2 x1): 1. blood glucose rise is detected (by the pancreas); 2. pancreas releases/secretes more insulin; 3. insulin causes liver/muscle cells to take up glucose; 4. glucose converted to glycogen (for storage). ALLOW insulin travels in the blood to target cells. IGNORE references to glucagon.
d) insulin is a protein (1) AND would be digested/broken down (by protease in the stomach/gut) (1) – both required for the mark [1] (AO2). ALLOW 'denatured by stomach acid' as an alternative to digestion.

(a)(i) Decrease = 380 - 19 = 361 cases per 100 000. Percentage decrease = \( \frac{361}{380} \times 100 = 95\% \).
(ii) With 91% of people vaccinated, few people carry and pass on the virus, so an unvaccinated person is less likely to come into contact with an infected person (herd immunity).
(b) Vaccine contains harmless antigens (weakened, dead or inactive pathogen). White blood cells (lymphocytes) detect the foreign antigens and produce complementary antibodies; memory cells remain. If the real pathogen later enters, memory cells cause a faster and larger antibody response, so the person does not become ill. When most of the population is immune, fewer people are infected and the chain of transmission is broken, so the disease spreads less, protecting those who cannot be vaccinated.

(a)(i) [2, AO2] Correct answer 95 (%) = 2 marks. If answer wrong: 380 - 19 = 361 (or 361/380) = 1 mark (method). ALLOW 95.0. ECF for a slip in subtraction.
(ii) [2, AO2] Any two from: most/many people are vaccinated / high vaccination rate (1); so fewer people are infected / fewer carriers / pathogen cannot pass on easily (1); so unvaccinated people are less likely to be exposed/infected (1); herd immunity named (1, AW). IGNORE 'they are immune' for unvaccinated people. Max 2.
(b)* [6, AO1 x4, AO2 x2] Levels of response, best fit.
Level 3 (5-6 marks): Detailed, correct explanation of both the effect on the individual (antigens, specific antibodies, memory cells, faster/larger secondary response) and the population effect (fewer infected people, reduced transmission, herd immunity). Logically structured, scientific terms used accurately.
Level 2 (3-4 marks): Correct explanation of the individual effect OR a partial account of both; some use of scientific terms; mostly clear.
Level 1 (1-2 marks): Simple statements, e.g. vaccine stops you getting ill / fewer people get ill; little or no linkage; limited use of scientific terms.
Level 0 (0 marks): No relevant content.
Indicative content (not a tick list): vaccine contains weakened/dead/inactive pathogen or antigens; does not cause the disease; lymphocytes recognise antigens; specific antibodies produced; memory cells formed; on later infection rapid, large antibody production; pathogen destroyed before symptoms; fewer infected people / fewer carriers; reduced transmission; herd immunity protects unvaccinated/vulnerable people. DO NOT ALLOW 'antibodies kill the virus by themselves' as a sole point at Level 3; DO NOT ALLOW vaccines containing antibiotics. IGNORE reference to antibiotics treating viruses.

(b) Radius = 18 ÷ 2 = 9 mm. Area = \( \pi \times 9^2 = 254.469... \) mm² = 254 mm² (3 s.f.). (e) Vaccine contains weakened/dead pathogen or antigens; white blood cells (lymphocytes) detect the antigens and make specific antibodies; memory cells remain so a later infection is met with a faster, larger antibody response. If many people are immune the pathogen cannot spread easily (herd immunity), so unvaccinated people are less likely to meet an infected person.

(a) 1 mark: microorganism/microbe that causes (infectious) disease. DO NOT ALLOW 'bacteria' only.
(b) 2 marks: correct answer 254 (mm²) = 2 marks. If incorrect, award 1 mark for r = 9 (mm) used in \( \pi r^2 \) (method). Using diameter 18 as radius gives 1018 (mm²): 0 marks. ALLOW 255 if \( \pi \) = 3.14 is not penalised only if unrounded value is shown; ALLOW ECF for method mark only.
(c) 1 mark: control / to show that water (or the paper disc) does not kill bacteria / so the effect of antibiotics can be compared. IGNORE 'to make it a fair test'.
(d) 1 mark: bacteria resistant to antibiotic C / antibiotic C does not kill (these) bacteria / antibiotic C ineffective.
(e)* 6 marks, levels of response. Indicative content: vaccine contains dead/weakened pathogen or antigens; no disease caused; antigens detected by white blood cells/lymphocytes; specific antibodies produced; memory cells formed; faster/larger secondary response on later infection by the same pathogen; high vaccination rate means most people immune; pathogen cannot spread easily / fewer carriers; chain of transmission broken (herd immunity); unvaccinated people less likely to be exposed.
Level 3 (5–6 marks): clear, detailed description of how immunity develops (antigens, antibodies, memory cells, faster response) AND a clear explanation of herd immunity with a link to reduced spread. Logical and well organised.
Level 2 (3–4 marks): describes some of the immune response with at least one correct detail, and attempts to explain protection of the unvaccinated, OR one part is detailed and the other only partly covered. Some structure.
Level 1 (1–2 marks): basic statements, e.g. vaccine makes you immune / fewer people get ill, with little scientific detail or linkage.
Level 0 (0 marks): no response worthy of credit.
AO1 = 4 marks (a, e), AO2 = 5 marks (b, c, d, e), AO3 = 2 marks (c, d).

(a)(i) 29 cm is much larger than the others (14–16 cm). (ii) (14 + 16 + 15 + 15) ÷ 4 = 60 ÷ 4 = 15.0 cm. (c) Receptor → sensory neurone → relay neurone (in the spinal cord/CNS) → motor neurone → effector. (d) Reflexes are automatic and bypass conscious thought in the brain, so the impulse takes a shorter pathway with fewer synapses.

(a)(i) 1 mark: 29 (cm) / trial 4.
(a)(ii) 2 marks: 15 (cm) = 2 marks. ALLOW 15.0. If incorrect, 1 mark for (14 + 16 + 15 + 15) = 60 or for dividing a correct sum of values by 4. Using 89 ÷ 5 = 17.8 scores 0.
(b) 2 marks, any two from: same ruler; same starting position/height of fingers; same release point/height; same person catching/releasing; same hand; same distraction/screen content (AW). IGNORE 'same time', 'same temperature'.
(c) 3 marks, any three from, in correct order: receptor detects stimulus (1); sensory neurone carries impulse to CNS/spinal cord (1); relay neurone connects sensory and motor neurones (1); motor neurone carries impulse to effector (1); effector/muscle contracts (to produce response) (1). Maximum 3. DO NOT ALLOW nerves/messages travel through 'veins'.
(d) 2 marks: does not involve conscious thought / brain (not needed to decide) (1); shorter pathway / fewer synapses / fewer neurones so less time (1). IGNORE 'automatic' alone.
(e) 1 mark: use of electronic/digital timer or light gate / use a computer-based reaction test / greater number of repeats to reduce effect of random error / use smaller scale calibrated in time (AW). IGNORE 'be more careful'.
AO1 = 3 marks (c), AO2 = 3 marks (b, d), AO3 = 5 marks (a, b, e).

(b) Decrease = 14.0 − 11.0 = 3.0 mmol/dm³. Time = 120 − 30 = 90 minutes. Rate = 3.0 ÷ 90 = 0.0333... = 0.033 mmol/dm³ per minute (2 s.f.). (c) The healthy person's pancreas releases enough insulin, so glucose is removed from the blood and returns to near normal by 120 min. The person with type 1 diabetes makes little or no insulin, so glucose rises higher and stays high, falling only slowly (probably through use in respiration and excretion).

(a) 1 mark: pancreas.
(b) 2 marks: 0.033 = 2 marks. If incorrect, 1 mark for 3.0 ÷ 90 or 14.0 − 11.0 = 3.0 (with 90 minutes used). ALLOW 0.03 for 1 mark only if working shown. ALLOW 0.0333 for 1 mark (not 2 s.f.).
(c) 3 marks, any three from: in healthy person, glucose rises then falls back to near the starting value by 120 minutes (1); pancreas releases insulin (1); insulin causes glucose to be taken into cells / converted to glycogen in the liver (1); person with type 1 diabetes has a higher peak/starts higher (1); pancreas makes little or no insulin / cannot make insulin (1); so glucose is not removed quickly and stays high/falls slowly (1). Must refer to both people for full marks; ORA.
(d) 2 marks, any two from: muscles use more glucose in respiration (1); lowering blood glucose concentration (1); cells become more sensitive to insulin (1); helps maintain healthy body mass, reducing the risk/severity of type 2 diabetes (1). IGNORE 'burns fat' alone.
(e) 2 marks: (insulin) causes liver and muscle cells/body cells to take up glucose (1); glucose is converted to glycogen for storage (1).
(f) 1 mark: glucagon. DO NOT ALLOW glycogen.
AO1 = 5 marks (a, e, f, part d), AO2 = 4 marks (b, c, d), AO3 = 2 marks (c).

a(i) Diameter 18 mm so radius = 9 mm. Area = \( \pi \times 9^2 = \pi \times 81 = 254.47 \) mm\(^2\) = 254 mm\(^2\) to 3 significant figures.

a(ii) Any two precautions, e.g. wash hands/wear gloves and disinfect the bench; keep the lid on and lift it only briefly; flame or sterilise the inoculating loop; use sterile agar and discs; tape the lid (not fully sealed) after inoculation.

b(i) The water disc is a control. It shows that the disc and the water do not kill bacteria, so any clear zones are caused by the antibiotics.

b(ii) No clear zone, so antibiotic Z does not kill or stop the growth of these bacteria: they are resistant to it.

c Random mutation produces a gene that makes a bacterium resistant. When an antibiotic is used, non-resistant bacteria are killed but resistant ones survive (natural selection), reproduce and pass on the resistance allele, so the resistant strain becomes common and can spread between people. Doctors should only prescribe antibiotics when necessary and avoid using them for viral infections; patients should complete the full course; hospitals should use hygiene measures and rotate or restrict use of antibiotics.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| a(i) | 254 (mm\(^2\)) | 2 | AO2 | Correct answer = 2 marks. If answer wrong or not 3 s.f., award 1 mark for radius = 9 mm used, or for \( \pi \times 9^2 \) / 254.469... ALLOW 1 mark for 254.5 or 255 (incorrect rounding) ECF only from a wrong radius used consistently, e.g. using 18 mm gives 1020 = 1 mark. |
| a(ii) | Any two from: wear gloves / wash hands / disinfect bench; lift lid only slightly / for a short time; sterilise the loop (in a flame) / use sterile equipment; tape the lid / do not open after incubation (AW) | 2 | AO1 | 1 mark each. IGNORE 'wear a lab coat' or 'keep clean' without detail. |
| b(i) | (It is a) control / shows that the disc / water / paper does not kill the bacteria (so clear zones are due to the antibiotic) (AW) | 1 | AO2 | ALLOW 'to compare with the antibiotic discs'. DO NOT ALLOW 'to make it a fair test' alone. |
| b(ii) | The bacteria are resistant to Z / Z does not kill the bacteria / Z is not effective (against them) | 1 | AO3 | DO NOT ALLOW 'Z is a weak antibiotic' alone. IGNORE 'immune'. |
| c* | Level 3 (5–6 marks): A detailed, correct explanation of the origin, selection and spread of resistance AND a description of at least two ways doctors and patients can slow it. Ideas are linked logically and clearly organised. Level 2 (3–4 marks): Explains most of the sequence (mutation, survival of resistant bacteria, reproduction) with at least one way to slow spread, OR describes several ways to slow spread with a partial explanation. Some logical linking. Level 1 (1–2 marks): Simple statements, e.g. bacteria become resistant or antibiotics should not be overused, with little or no linking. Level 0 (0 marks): no response worthy of credit. Indicative content: random mutation gives a resistance allele; antibiotic kills non-resistant bacteria; resistant bacteria survive (selection); they reproduce and pass on the allele; the resistant strain increases in frequency and spreads between people; doctors should not prescribe antibiotics for viral infections or unnecessarily; use narrow-spectrum/appropriate antibiotic; patients should complete the course; good hygiene/isolation in hospitals; research into new antibiotics. Guidance: scientific content decides the level; clarity and organisation decide the mark within the level. DO NOT ALLOW 'bacteria become immune' or 'bacteria adapt/get used to the antibiotic' as a mechanism, although the rest of the answer may still be credited. | 6 | AO1 ×3, AO2 ×3 | Best-fit judgement. |

A vaccine contains a harmless form of the pathogen's antigens. This causes lymphocytes to make memory cells. On a second exposure, memory lymphocytes rapidly produce the specific antibodies, so the answer is B. Antibiotics do not act on viruses, phagocytes engulf rather than make toxins, and platelets are involved in clotting.

B (1 mark, AO1). Accept no other option. A, C and D are incorrect: antibiotics do not kill viruses; phagocytes ingest pathogens; platelets help blood clotting.

The impulse travels from the receptor along a sensory neurone to a relay neurone in the spinal cord, then along a motor neurone to the effector (a muscle). This is option D.

D (1 mark, AO1). All other sequences place at least one component in the wrong order.

High blood glucose is detected by the pancreas, which secretes insulin. Insulin causes the liver and muscles to take up glucose and store it as glycogen, lowering blood glucose. This is A.

A (1 mark, AO1). B, C and D each contain the wrong hormone or the wrong direction of conversion.

The radius is half the diameter: \(r = 20 \div 2 = 10\) mm. Area \(= \pi \times 10^2 = 314.16\), which is 314 mm\(^2\) to the nearest whole number. Answer C.

C (1 mark, AO2). Common errors: A uses \(\pi \times 20\); B uses \(2\pi \times 20\); D uses the diameter as the radius, \(\pi \times 20^2\).

High temperatures break bonds holding the enzyme in shape, so the active site is altered (the enzyme is denatured). The substrate can no longer bind. Answer B.

B (1 mark, AO1). Enzymes are not used up (C); heating makes molecules move faster, not slower (D); substrate size does not change (A).

The cross is Gg × gg. Gametes: G or g from one parent, g only from the other. Offspring are Gg and gg in equal numbers, so half (50%) are gg and brown. Answer C.

C (1 mark, AO2). B and D result from using a Gg × Gg cross; A assumes no brown offspring are possible.

Keeping animals warm and limiting movement reduces energy lost as heat and used for movement, so more energy from food is used for growth. Answer A.

A (1 mark, AO1). Chickens do not photosynthesise (B); digestion rate and protein need are not the reason given (C, D).

Increased sweating allows evaporation, which transfers energy from the skin. Vasodilation of skin blood vessels increases blood flow near the surface so more heat is radiated. Answer D.

D (1 mark, AO1). Each other option includes at least one response that would conserve heat rather than lose it.

A vaccine contains dead or weakened pathogens (or their antigens). These stimulate white blood cells to make specific antibodies and memory cells, so a later infection is met with a faster, larger response. Option B is therefore correct.

B = 1 mark. A is wrong: vaccines stimulate the person's own antibody production (passive immunity is not involved). C is wrong: antibiotics are not in vaccines. D is wrong: vaccines do not contain white blood cells. Any answer other than B = 0 marks.

Magnification = \( 45 \div 0.30 = 150 \). The magnification is \( \times 150 \), option C.

C = 1 mark. Distractors come from decimal-place slips (A, D) and subtraction instead of division (B is not a valid method). Any answer other than C = 0 marks.

In a reflex arc a receptor detects the stimulus, a sensory neurone carries the impulse to the CNS, a relay neurone connects within the CNS, a motor neurone carries the impulse to the effector (muscle), which produces the response. Only D lists this complete sequence correctly.

D = 1 mark. A, B and C each have neurones or structures in the wrong order. Any answer other than D = 0 marks.

High temperature breaks bonds holding the enzyme's protein structure, so the active site changes shape (denaturation). The substrate can no longer bind, so the reaction stops. Option A is correct.

A = 1 mark. B is wrong as substrate size does not change. C is wrong as enzymes are not used up. D is wrong as heating increases particle movement. Any answer other than A = 0 marks.

Thyroxine is released by the thyroid gland. Adrenaline comes from the adrenal glands, insulin from the pancreas and oestrogen from the ovaries, so only C is correct.

C = 1 mark. A, B and D each pair a hormone with the wrong gland. Any answer other than C = 0 marks.

Ladybirds are predators of aphids. Using a living organism to reduce a pest population is biological control, option B.

B = 1 mark. A, C and D describe unrelated techniques. Any answer other than B = 0 marks.

Both parents are Ff. The possible offspring genotypes are FF, Ff, Ff and ff in equal proportions. Only ff has cystic fibrosis, so the probability is 1 in 4 = 25%.

D = 1 mark. B is the proportion of carriers; C is the proportion without the disorder. Any answer other than D = 0 marks.

a)i) Radius = 18 ÷ 2 = 9 mm. Area = \( \pi \times 9^2 = \pi \times 81 = 254.47... \) mm², which is 254 mm² to 3 significant figures.

a)ii) The sterile water disc is a control. It shows that the disc itself (or the water) does not stop bacteria growing, so the clear zones around P and Q are due to the antibiotics.

b) Mutation produces a gene/allele that makes some bacteria resistant. When the antibiotic is present, non-resistant bacteria are killed but resistant bacteria survive (natural selection). The survivors reproduce, passing the resistance allele to offspring, so the population becomes mainly resistant.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| a)i) | 254 (mm²) | 2 | AO2 | Correct final answer to 3 s.f. scores 2 marks. If answer is incorrect or not to 3 s.f., award 1 mark for radius = 9 (mm) used in \( \pi r^2 \) (e.g. 254.47 or 250 earns 1). ALLOW 255 only if from 254.5 and shown. ECF: if radius is wrongly taken as 18 mm, ALLOW 1 mark for 1020 (mm²) (1017.9 to 3 s.f.). IGNORE missing units if the units are printed on the answer line. |
| a)ii) | (it is) a control (1) to show that the disc / water does not affect the growth of bacteria (AW) | 1 | AO3 | Need the idea of a comparison or of showing the effect is due to the antibiotic. IGNORE 'to make it a fair test' on its own. |
| b) | any two of: (random) mutation (in bacterial DNA/gene) gives resistance (1); non-resistant bacteria are killed by the antibiotic / resistant bacteria survive (1); resistant bacteria reproduce and pass on the resistance allele/gene (1); proportion/number of resistant bacteria increases (AW) (1) | 2 | AO1 | MAX 2. ALLOW natural selection for the idea of survival of the resistant bacteria. DO NOT ALLOW bacteria 'adapt' / 'become used to' the antibiotic / the individual bacteria mutate because they need to. |

(a)(i) The pancreas monitors blood glucose and secretes insulin.
(ii) Increase = 11.0 − 5.0 = 6.0 mmol/dm\(^3\). Percentage increase = \(\frac{6.0}{5.0} \times 100 = 120\)%.
(b) Insulin binds to target cells (liver and muscle), which take up glucose from the blood. In the liver, glucose is converted to glycogen, so blood glucose falls.
(c) Insulin is a protein. In the stomach and small intestine, protease enzymes would digest it into amino acids, so it could not act as a hormone in the blood. Injection places it directly into the bloodstream.

(a)(i) pancreas [1]. DO NOT ALLOW pancreatic islets alone without organ; ALLOW islets of Langerhans in the pancreas. AO1.

(a)(ii) Correct answer 120 (%) [2] (AO2). If the answer is incorrect, award 1 mark for 6.0 (÷ 5.0) \(\times\) 100 or for the change of 6.0. ALLOW 1.2 \(\times\) 100. DO NOT ALLOW 54.5 or 55 (division by 11.0): award the method mark only for 6.0 seen. ECF applies only to a wrongly read value in the subtraction.

(b) Any two from: (AO1)
- insulin causes cells / liver / muscle cells to take up glucose (from the blood) [1]
- liver converts glucose to glycogen [1]
- glycogen is stored (in the liver / muscles) [1]
- (more) glucose used in respiration AW [1]
IGNORE 'insulin breaks down glucose'. DO NOT ALLOW 'converts glucose to glucagon'.

(c) Any two from: (AO2)
- insulin is a protein [1]
- digested / broken down by protease (enzymes) in the stomach / small intestine / gut [1]
- (so) not absorbed into the blood as insulin / would not reach target cells AW [1]
IGNORE 'stomach acid kills it' alone. DO NOT ALLOW 'insulin is an enzyme being digested' as a contradiction of being a protein hormone.

Total 7 marks: AO1 = 3, AO2 = 4.

(b) Radius = 16 / 2 = 8 mm. Area = \( \pi \times 8^2 = 201.06... \) = 201 mm\(^2\) (3 s.f.).
(a), (c), (d) are explanations as in the marking scheme.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| (a) | to prevent contamination (of the culture) by other microorganisms / bacteria from the air or surroundings; OR to stop harmful bacteria being released | 1 | AO1 | ALLOW so only the named bacterium grows. IGNORE 'to keep it sterile' alone. |
| (b) | correct final answer 201 (mm\(^2\)) = 2 marks. Otherwise: radius = 8 (mm) / \( \pi \times 8^2 \) seen = 1 mark | 2 | AO2 | ALLOW 200.96 to 201.1 before rounding. Unrounded value 201.06 with no rounding to 3 s.f. = 1 mark. If 16 used as radius (804) = 1 mark. No ECF beyond a wrong radius used correctly. |
| (c)(i) | it is a control / shows water (or the disc) does not affect bacterial growth, so the clear zones are caused by the antibiotics | 1 | AO3 | DO NOT ALLOW 'to make it a fair test' alone. |
| (c)(ii) | P has the largest clear zone / diameter (16 mm), so it killed / inhibited the bacteria over the greatest area (AW) | 1 | AO3 | ALLOW comparison with Q (10 mm) and R (0 mm). |
| (d) | any three of: (random) mutation produces a resistant bacterium / allele (1); antibiotic kills non-resistant bacteria (1); resistant bacteria survive / are selected (1); resistant bacteria reproduce / pass on the resistance allele to offspring (1); proportion of resistant bacteria increases (in the population) (1) | 3 | AO1 | Max 3. DO NOT ALLOW 'bacteria become used to / adapt to the antibiotic' or 'the bacteria choose to mutate'. |

a(i) Any aseptic technique, e.g. sterilise the loop in a flame, keep the lid of the dish closed as much as possible, disinfect the work surface.
a(ii) Human pathogens grow best at body temperature, 37 \(^\circ\)C; at 25 \(^\circ\)C they are much less likely to multiply, so the risk of culturing harmful bacteria is reduced.
b(i) Mean = \((12 + 14 + 13) \div 3 = 39 \div 3 = 13\) mm.
b(ii) Radius = \(13 \div 2 = 6.5\) mm. Area = \(\pi \times 6.5^2 = \pi \times 42.25 = 132.7\) mm\(^2\) = 133 mm\(^2\) (3 s.f.).
c Mouthwash A has the largest mean clear zone (13 mm compared with 8 mm for B and 0 mm for C), so it killed or stopped the growth of the most bacteria.
d It is a control: it shows that any clear zone is caused by the mouthwash and not by the paper disc or the liquid used, allowing a fair comparison.

| Q | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| a(i) | Any one: flame/sterilise the loop or spreader; keep lid closed/only slightly open; sterilise surfaces/hands; use sterile agar and dishes | 1 | AO1 | ALLOW any sensible aseptic technique. IGNORE 'wear gloves' alone. |
| a(ii) | Human pathogens grow best at/near body temperature (37 \(^\circ\)C) (1); at 25 \(^\circ\)C they are less likely to grow/multiply, so harmful bacteria are less likely to be cultured (1) | 2 | AO1 + AO2 | ALLOW 'disease-causing bacteria/microorganisms' for pathogens. DO NOT ALLOW 'bacteria are killed at 37 \(^\circ\)C'. |
| b(i) | 13 (mm) = 2 marks. Method: \((12+14+13) \div 3\) or 39 \(\div\) 3 (1) | 2 | AO2 | Correct answer without working scores 2. |
| b(ii) | 133 (mm\(^2\)) = 2 marks. Method: \(\pi \times 6.5^2\) / radius = 6.5 (1) | 2 | AO2 | ALLOW 132.7 or 132.73 for 1 mark only if not rounded to 3 s.f. ALLOW ECF from b(i): radius = (b(i) answer) \(\div\) 2 then area to 3 s.f. for 2 marks. Using diameter as radius (\(\pi \times 13^2\) = 531) scores 0. Unit not required. |
| c | Mouthwash A (1); largest (mean) clear zone/diameter/area (1) | 2 | AO3 | Second mark depends on A being chosen. ALLOW 'kills most bacteria' as reason. |
| d | Control / to show the disc or water does not kill bacteria / to show that the clear zone is due to the mouthwash / for comparison | 1 | AO3 | ALLOW 'to show no bacteria killed without mouthwash'. IGNORE 'to make it a fair test' alone. |

a(i) The pancreas.
a(ii) Increase = \(14.5 - 9.0 = 5.5\) mmol/dm\(^3\). Percentage increase = \(\dfrac{5.5}{9.0} \times 100 = 61.1\)%, so 61%.
b* Type 1: the pancreas fails to make enough insulin (the insulin-producing cells are destroyed), so glucose is not taken up and converted to glycogen in the liver and muscles; treated by injecting insulin at mealtimes, checking blood glucose and controlling carbohydrate intake. Type 2: body cells no longer respond properly to insulin (insulin resistance), often linked to obesity, poor diet and inactivity; managed by a diet low in refined carbohydrate, regular exercise and weight loss, and sometimes drugs or insulin.

| Q | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| a(i) | Pancreas | 1 | AO1 | DO NOT ALLOW 'liver'. |
| a(ii) | 61 (%) = 3 marks. Increase = 14.5 \(-\) 9.0 = 5.5 (1); \(5.5 \div 9.0 \times 100\) (1); rounded to 61 (1) | 3 | AO2 | Correct answer without working scores 3. ALLOW 61.1 for 2 marks only. ECF for a wrong subtraction. Using 5.5 \(\div\) 14.5 (= 38%) scores 1 mark (for 5.5). |
| b* | Level 3 (5-6 marks): Clear comparison of the causes of both types AND explanation of management of both types, including the role of insulin. Linked, logical, scientifically accurate. Level 2 (3-4 marks): Describes causes of both types OR management of both with some explanation; may be partly imbalanced. Level 1 (1-2 marks): Some relevant points about causes or management of one or both types, with little linking or explanation. Level 0 (0 marks): no response worthy of credit. | 6 | AO1 x3 + AO2 x3 | Indicative content: Causes: Type 1: pancreas does not produce (enough) insulin / insulin-producing cells destroyed. Type 2: body cells do not respond to insulin (insulin resistance) / less sensitive; risk linked to obesity, poor diet, inactivity. Management: Type 1: insulin injections (or pump), usually with meals; monitor blood glucose; control carbohydrate intake and exercise; insulin allows glucose uptake by cells/conversion to glycogen in liver. Type 2: reduce carbohydrate/sugar intake, balanced diet; increase exercise; lose weight; sometimes medication to improve response to insulin or lower glucose. Within a level, clarity, linking and organisation decide the mark. ALLOW 'beta cells'. IGNORE reference to glucagon unless used correctly. |

(a) Sterilise the loop in a flame and keep the dish lid mostly closed to prevent contamination from the air.
(b)(i) Radius = 26 ÷ 2 = 13 mm. Area = \(\pi \times 13^2 = 530.9\) mm² = 531 mm² (3 s.f.).
(ii) Antibiotic B has the largest clear zone (26 mm), so it killed the most bacteria.
(c) The sterile water disc is a control showing that the paper disc and the liquid have no effect on the bacteria.
(d) At 37 °C, bacteria that are harmful to humans could grow, so a lower temperature is used for safety.
(e) Influenza is a viral infection. Viruses live and reproduce inside host cells and antibiotics do not target them.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| (a) | any two from: flame/sterilise the inoculating loop (before and after use) (1); sterilise the agar/dish/equipment before use (1); keep lid on/only lift the lid slightly (1); disinfect the bench/wash hands (1) | 2 | AO1 | ALLOW AW for correct aseptic ideas. IGNORE 'wear gloves' on its own. |
| (b)(i) | 531 (mm²) | 3 | AO2 | Award 3 marks for the correct final answer. If the answer is incorrect: radius = 13 (mm) (1); \(\pi \times 13^2\) / 530.9 (1) for correct unrounded value. ALLOW 530 (mm²) if working is shown, for 2 marks. If 26 is used as the radius, area = 2124 gives max 1 mark for correct use of \(\pi r^2\) (ECF only for this case). Rounding must be to 3 s.f. for the third mark. |
| (b)(ii) | B (1) with reason: largest clear zone / largest diameter (1) | 1 | AO3 | Both antibiotic and reason are required for the mark. DO NOT ALLOW 'biggest area' unless B is identified. |
| (c) | control / to show that the disc (or water) does not kill the bacteria (1) | 1 | AO2 | ALLOW to show the clear zones are caused only by the antibiotics / for comparison. |
| (d) | 37 °C is close to body temperature (1); (so) pathogens/harmful bacteria could grow (1) | 2 | AO2 | ALLOW AW 'disease-causing'. IGNORE 'to keep it safe' on its own. |
| (e) | influenza is caused by a virus (1); antibiotics only kill bacteria / do not affect viruses (1) | 2 | AO1/AO2 | ALLOW viruses live inside cells so antibiotics cannot reach them. DO NOT ALLOW 'viruses are resistant' without further explanation. |

(a)(i) The pancreas makes insulin. (ii) Glucagon is released when blood glucose is too low and causes the liver to break down glycogen to glucose.
(b) Insulin is a protein, so protease enzymes in the digestive system would digest it into amino acids before it could enter the blood. Injection places it directly in the blood.
(c) Glucose from digested carbohydrate is absorbed, raising blood glucose. Receptors in the pancreas detect the rise and the pancreas secretes insulin. Insulin travels in the blood to the liver and muscles, where glucose is taken into cells and converted to glycogen. Blood glucose falls to normal and insulin release decreases (negative feedback). In untreated type 1 diabetes, too little insulin is made, so the liver cells do not take up glucose or store it as glycogen and the concentration stays high.
(d) Amino acids.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| (a)(i) | pancreas | 1 | AO1 | DO NOT ALLOW pancreases/pancreatic cells only if organ is contradicted. |
| (a)(ii) | glucagon | 1 | AO1 | DO NOT ALLOW glycogen. |
| (b) | insulin is a protein (1); (would be) digested/broken down by protease/enzymes in the stomach/gut (1) | 2 | AO2 | ALLOW AW 'denatured by stomach acid' for second mark. IGNORE 'it works faster'. |
| (c)* | Level of response, 6 marks. Level 3 (5–6 marks): a clear, logically ordered account that explains the response of the healthy person (glucose rise detected, pancreas releases insulin, liver/muscle cells take up glucose and store as glycogen, blood glucose falls) AND explains why untreated type 1 diabetes leaves glucose high (insufficient insulin so no uptake/storage). Organs, hormones and target tissues are all linked. Level 2 (3–4 marks): a mostly correct account of the healthy response with some linking of organ, hormone and target, with a limited or incomplete explanation for diabetes; or a good account of one part only with partial reference to the other. Level 1 (1–2 marks): some relevant statements, e.g. insulin lowers blood glucose / pancreas involved, with little linking or explanation. Level 0 (0 marks): no response or no response worthy of credit. | 6 | AO1 ×3 AO2 ×3 | Indicative content: glucose absorbed so blood glucose rises; detected by pancreas; insulin secreted into the blood; carried to liver and muscles/target cells; glucose taken into cells; converted to glycogen (stored); blood glucose falls to normal; negative feedback; type 1: pancreas does not make enough insulin / cells destroyed; glucose not taken up / not converted to glycogen; blood glucose stays high. Best-fit judgement: scientific content determines the level; clarity and logical organisation determine the mark within the level. Do not penalise omission of the term 'negative feedback'. |
| (d) | amino acids | 1 | AO1 | DO NOT ALLOW 'amino acid chains' or 'polypeptides'. |

a Any precaution, e.g. keep the lid of the Petri dish closed as far as possible / sterilise the spreader in a flame / work near a Bunsen flame.

b i Mean = \((14 + 16 + 15) \div 3 = 15\) mm.

b ii Radius = \(15 \div 2 = 7.5\) mm. Area = \(\pi \times 7.5^2 = \pi \times 56.25 = 176.7\) mm², which is 177 mm² to 3 significant figures.

c The garlic extract diffuses out of the disc into the agar. It contains a substance that kills the bacteria or stops them growing/reproducing, so no lawn forms close to the disc.

d Disc 3 is a control. It shows that the disc and the water do not affect bacterial growth, so any clear zone around disc 1 is caused by the garlic.

e Mutation produces a gene/allele that makes a bacterium resistant. When antibiotics are used, non-resistant bacteria are killed but resistant bacteria survive, reproduce and pass the allele on. The resistant strain becomes more common (natural selection). It can spread between people. Reduce by: doctors not prescribing antibiotics for viral infections or minor infections; patients completing the full course; restricting use of antibiotics in farming; hygiene to reduce spread; developing new antibiotics.

| Question | Answer | Marks | AO | Guidance |
|---|---|---|---|---|
| a | any one precaution to prevent airborne contamination, e.g. lid kept on / only lifted slightly; work near a Bunsen flame; sterilise loop/spreader by flaming | 1 | AO1 | ALLOW wear gloves / wash hands. DO NOT ALLOW 'wear a mask' alone. IGNORE 'clean the bench' alone. |
| b i | 15 (mm) | 1 | AO2 | Correct answer only. |
| b ii | 177 (mm²) = 2 marks. If answer incorrect, award 1 mark for radius 7.5 mm used in \(\pi r^2\) / 176.7 / 176.71 seen | 2 | AO2 | ALLOW 176.7 for 1 mark only if not rounded to 3 s.f. ALLOW ECF from an incorrect mean in b i for both marks if calculated correctly and rounded to 3 s.f. ALLOW 707 (1 mark: diameter used as radius). |
| c | garlic (extract) diffuses into the agar / spreads out from the disc (1); (it contains a substance that) kills bacteria / prevents bacteria growing/reproducing (1) | 2 | AO1 / AO2 | ALLOW antibacterial / antimicrobial chemical from the garlic. IGNORE 'kills the disc'. |
| d | (it is a) control (1) | 1 | AO3 | ALLOW to show water / the paper disc does not kill bacteria / to show the effect is due to garlic extract / for comparison. DO NOT ALLOW 'to keep it a fair test' alone. |
| e* | Level of response (6 marks). Level 3 (5–6 marks): a clear, detailed and logical discussion covering BOTH how resistance develops (mutation, selection by antibiotic, survival and reproduction of resistant bacteria, allele passed on) AND at least two sensible measures for doctors/patients, with links made between the measures and the cause. Level 2 (3–4 marks): some correct explanation of how resistance develops with at least one measure to reduce it, OR a detailed account of development only; some linking, mostly logical. Level 1 (1–2 marks): simple statements, e.g. bacteria become resistant, or antibiotics should not be overused, with little or no explanation; limited structure. Level 0 (0 marks): no response worthy of credit. | 6 | AO1 x3 / AO2 x3 | Indicative content: random mutation gives resistance allele; antibiotic kills non-resistant bacteria; resistant bacteria survive and reproduce, passing on allele; resistant strain becomes the majority (natural selection); spread of resistant strain (e.g. MRSA); doctors avoid prescribing for viral/mild infections; patients complete the full course; reduced agricultural use; hygiene/isolation; new antibiotics developed. Scientific content decides the level; clarity, relevance and logical organisation decide the mark within the level. Use best fit. |