2022 May/June · Paper 33 · Q9 (a, b, c)7 marksSense organs: the eye
2022 May/June · Paper 42 · Q2 (c(i), c(ii))4 marksBlood glucose control & diabetes · Homeostasis & negative feedback (general)
2022 May/June · Paper 42 · Q3 (a(i), a(ii), b(i), b(ii))11 marksSense organs: the eye
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or see the official Cambridge past-papers page; for other papers, ask your
school. “Paper 42” means Paper 4, variant 2.
Practice questions
Original questions written by HomiLabs in the style of the exam, with answers and mark schemes. They are not
Cambridge past paper questions and have not been reviewed by Cambridge. Try each one before opening the answer.
Q1Sense organs: the eye · Core · Paper 4 style · 5 marks
(a)State the function of each part of the eye:(i) cornea(ii) iris(iii) lens(iv) retina(v) optic nerve[5]
Show answer
(a) (i) refracts (bends) light entering the eye; (ii) controls how much light enters (changes pupil size); (iii) focuses light onto the retina (fine focusing); (iv) contains light receptors (rods and cones); (v) carries nerve impulses from the retina to the brain.
B1 each.
Q2Sense organs: the eye · Core · Paper 4 style · 5 marks
(a)Compare rods and cones, stating for each the light conditions in which it works best, whether it detects colour, and where it is mainly found in the retina.[4]
(b)Explain why it is difficult to see the colours of objects at night.[1]
Show answer
(a) Rods: work in dim light; black and white only (no colour); found throughout the retina but not at the fovea. Cones: work in bright light; detect colour (three types); concentrated in the fovea.
(b) Cones do not work in dim light; only rods respond, and rods do not detect colour.
B1.
Q3Sense organs: the eye · Standard · Paper 4 style · 5 marks
A student leaves a dark cinema hall in Islamabad and walks out into bright sunlight.
(a)Describe and explain the changes in the iris when the student walks into the bright sunlight.[3]
(b)State the type of response this is and why it is useful that it is automatic.[2]
Show answer
(a) Circular muscles of the iris contract; radial muscles relax; pupil becomes smaller (constricts), so less light enters and the retina is protected from damage.
B1 circular contract; B1 radial relax; B1 pupil smaller so less light enters / protects retina.
(b) A reflex (involuntary) action; it is very fast and does not need thought, so the retina is protected immediately.
B1 reflex; B1 fast / no conscious thought.
Q4Sense organs: the eye · Standard · Paper 2 style · 1 mark
For a near object the ciliary muscles contract, the suspensory ligaments slacken and the elastic lens becomes fatter (more convex) to refract light more. A describes focusing on a distant object.
Q5Sense organs: the eye · Challenge · Paper 4 style · 5 marks
A man on a train is reading messages on his phone, then looks out of the window at hills several kilometres away.
(a)Describe the changes in the eye that allow the man to focus on the distant hills after looking at his phone.[3]
(b)Explain why the lens must change shape for the image to be focused on the retina.[2]
Show answer
(a) Ciliary muscles relax; suspensory ligaments are pulled tight (tension increases); lens is pulled thinner / less convex.
B1 each.
(b) Light from a distant object needs less refraction (rays almost parallel); a thinner lens refracts light less, so the image is focused on the retina rather than in front of it.
B1 distant object needs less refraction / bending; B1 thinner lens bends light less to focus on retina.
Q6Sense organs: the eye · Challenge · Paper 6 style · 5 marks
A volunteer's pupil was photographed after two minutes at each light intensity and its diameter measured.Light intensity / lux : pupil diameter / mm50 : 6.4200 : 4.8500 : 3.61000 : 2.4
(a)Calculate the percentage decrease in pupil diameter between 50 lux and 1000 lux.[2]
(b)Describe the relationship between light intensity and pupil diameter.[1]
(c)Suggest why the volunteer stayed at each light intensity for two minutes before the photograph was taken.[1]
(d)Suggest one variable, other than light intensity, that should be kept constant.[1]
Show answer
(a) 62.5 %
(6.4 − 2.4) ÷ 6.4 × 100 (M1) = 62.5 % (A1).
(b) As light intensity increases, pupil diameter decreases (not in direct proportion).
B1.
(c) To allow time for the pupil to adjust fully / reach a steady size.
B1.
(d) Distance of the light from the eye / same eye measured / same volunteer / same direction of light / looking at the same object at the same distance.
B1.
Q7Nervous system & reflex arc · Core · Paper 4 style · 4 marks
A girl accidentally touches a hot tawa (griddle) and pulls her hand away before she feels pain.
(a)Put these in the order an impulse passes along a reflex arc, starting with the receptor:motor neurone, effector (muscle), relay neurone, receptor, sensory neurone[2]
(c) It is very fast / automatic, so damage to the body is reduced.
B1.
Q8Nervous system & reflex arc · Standard · Paper 6 style · 5 marks
A student measures his reaction time. A partner drops a metre ruler between his finger and thumb, and he catches it as quickly as possible. The distance the ruler falls is recorded.Trial : distance / cm1 : 182 : 153 : 214 : 165 : 15reaction time (s) = √(2d ÷ 9.8), where d is the distance in metres.
(a)Calculate the mean distance fallen.[1]
(b)Use the formula to calculate the reaction time for the mean distance. Give your answer to 2 significant figures.[2]
(c)Explain why this is not a reflex action.[2]
Show answer
(a) 17 cm
B1.
(b) 0.19 s
d = 0.17 m (M1); t = √(2 × 0.17 ÷ 9.8) = 0.1863 → 0.19 s (A1).
(c) The response involves the brain and is a conscious decision (voluntary), so it is slower than a reflex.
B1 involves brain / conscious; B1 voluntary / not automatic.
Q9Nervous system & reflex arc · Challenge · Paper 4 style · 5 marks
A patient has damage to the motor neurones that run from the spinal cord to the muscles of his left leg. The sensory neurones are not damaged.
(a)Explain why the patient can feel a pin prick on his foot but cannot move his foot away.[3]
(b)State the difference between a voluntary action and a reflex action.[2]
Show answer
(a) Receptors and sensory neurones still work, so impulses travel to the spinal cord and up to the brain (pain felt); but impulses cannot travel along the damaged motor neurones to the leg muscles (effectors), so no movement.
(b) Voluntary: involves conscious thought / the brain decides, slower. Reflex: automatic, no conscious thought, faster.
B1 each.
Q10Hormones & adrenaline · Core · Paper 4 style · 5 marks
(a)Define the term hormone.[2]
(b)Name the gland that secretes each hormone: (i) adrenaline, (ii) testosterone, (iii) oestrogen.[3]
Show answer
(a) A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.
B1 chemical made by gland; B1 carried in blood to target organ(s).
(b) (i) adrenal gland; (ii) testes; (iii) ovaries.
B1 each.
Q11Hormones & adrenaline · Standard · Paper 4 style · 5 marks
A cricket batter is about to face a very fast bowler in front of a large crowd in Lahore. His adrenal glands release adrenaline.
(a)State three effects of adrenaline on the body.[3]
(b)Explain how one of these effects helps the batter to react to the ball.[2]
Show answer
(a) Any three of: increased heart rate (pulse); increased breathing rate; dilated pupils; increased blood glucose concentration.
1 mark each.
(b) e.g. higher heart rate / blood glucose supplies more oxygen and glucose to muscles; faster respiration releases more energy for muscle contraction.
B1 more oxygen / glucose to muscles; B1 more respiration / energy for movement.
Q12Hormones & adrenaline · Challenge · Paper 4 style · 5 marks
(a)Compare nervous control with hormonal control. Give three differences.[3]
(b)Suggest why control of blood glucose is better done by hormones than by nerves.[2]
Show answer
(a) Nervous: electrical impulses / hormonal: chemicals; nervous: along neurones / hormonal: in the blood; nervous: very fast / hormonal: slower; nervous: short-lived effect / hormonal: longer-lasting; nervous: precise target / hormonal: may affect several organs.
1 mark each for a correct comparison, max 3. Both sides needed for each mark.
(b) The response needs to last a long time and affect organs throughout the body (liver, muscles); speed is not essential, and hormones in the blood reach all target cells.
Q13Tropic responses & auxin · Core · Paper 4 style · 4 marks
A potted plant is left on a windowsill.
(a)Define the terms (i) phototropism and (ii) gravitropism.[2]
(b)State whether a shoot shows positive or negative phototropism and positive or negative gravitropism.[2]
Show answer
(a) (i) a growth response of a plant to the direction of light; (ii) a growth response of a plant to gravity.
B1 each; must refer to growth response.
(b) Positive phototropism (grows towards light); negative gravitropism (grows away from gravity / upwards).
B1 each.
Q14Tropic responses & auxin · Standard · Paper 4 style · 4 marks
(a)Explain how auxin causes a shoot to grow towards light coming from one side.[4]
Show answer
(a) Auxin is made in the shoot tip; it diffuses down the shoot; auxin moves to / accumulates on the shaded side; auxin stimulates cell elongation, so cells on the shaded side grow longer and the shoot bends towards the light.
1 mark each: made in tip; diffuses down; more on shaded side; stimulates cell elongation on shaded side → bending.
Q15Tropic responses & auxin · Standard · Paper 2 style · 1 mark
(a)[1]
Show answer
(a) B Auxin collects on the lower side, so cells on the lower side elongate more.
In a horizontal shoot auxin accumulates on the lower side; it stimulates cell elongation there, so the lower side grows faster and the shoot curves upwards (negative gravitropism).
Q16Tropic responses & auxin · Challenge · Paper 6 style · 6 marks
Three groups of five oat seedlings were lit from one side for 6 hours. In group 1 the seedlings were untreated; in group 2 the tip of each shoot was covered with a foil cap; in group 3 the tip was cut off. The angle by which each shoot bent towards the light was measured.Group : angles / °untreated : 32, 28, 35, 30, 25foil cap on tip : 2, 0, 1, 0, 2tip removed : 0, 0, 1, 0, 0
(a)Calculate the mean angle of curvature for each group.[2]
(b)Explain what the results show about where light is detected and where auxin is made.[3]
(c)Explain why each group contained five seedlings.[1]
Show answer
(a) untreated 30°; foil cap 1°; tip removed 0.2°
M1 sum ÷ 5; A1 all three correct.
(b) Light is detected by the tip: covering the tip stops bending although the rest of the shoot is exposed; removing the tip stops bending, so the tip produces the substance (auxin) that causes bending.
B1 tip detects light (foil result); B1 tip produces auxin / growth substance (tip-removed result); B1 comparison with untreated control.
(c) To calculate a mean / reduce the effect of individual variation / identify anomalies.
B1.
Q17Blood glucose control & diabetes · Core · Paper 4 style · 4 marks
(a)Name the organ that secretes insulin and glucagon.[1]
(b)Describe the role of insulin when blood glucose concentration rises after a meal.[2]
(c)State the effect of glucagon on the liver.[1]
Show answer
(a) Pancreas.
B1.
(b) Insulin is secreted into the blood; it causes liver and muscle cells to take up glucose and convert it to glycogen (storage), so the blood glucose concentration falls.
B1 glucose taken up by liver / muscle; B1 converted to glycogen / blood glucose falls.
(c) Liver converts (breaks down) glycogen into glucose, which is released into the blood.
B1.
Q18Blood glucose control & diabetes · Standard · Paper 4 style · 5 marks
A 12-year-old boy in Quetta is diagnosed with type 1 diabetes.
(a)State the cause of type 1 diabetes.[1]
(b)State two symptoms of type 1 diabetes.[2]
(c)Describe how type 1 diabetes is treated.[2]
Show answer
(a) The pancreas does not produce (enough) insulin, because the insulin-secreting cells are destroyed (by the body's immune system).
B1.
(b) Any two of: high blood glucose; glucose in the urine; thirst; frequent urination; tiredness; weight loss; blurred vision.
1 mark each.
(c) Regular injections of insulin (or insulin pump); monitoring blood glucose concentration; controlling diet (carbohydrate intake) and exercise.
B1 insulin injections; B1 any other: monitor glucose / control diet / regular meals.
Q19Blood glucose control & diabetes · Standard · Paper 2 style · 1 mark
(a)[1]
Show answer
(a) B Insulin is secreted and the liver converts glucose to glycogen.
Digested starch raises blood glucose, so the pancreas secretes insulin, which makes the liver store glucose as glycogen. A describes the response to low blood glucose.
Q20Blood glucose control & diabetes · Challenge · Paper 4 style · 7 marks
Two people drank a glucose drink after fasting overnight. Their blood glucose concentration (mmol/dm³) was measured.Time / min : person A : person B0 : 5.0 : 6.230 : 7.8 : 12.460 : 6.4 : 12.9120 : 5.2 : 11.0
(a)Calculate the percentage increase in blood glucose concentration from 0 to 30 minutes for each person.[2]
(b)Suggest which person has type 1 diabetes. Use the data to explain your answer.[3]
(c)Explain why the blood glucose of person A returns to normal by 120 minutes.[2]
(b) Person B; glucose rises much higher (to 12.4) and is still high (11.0) after 120 minutes; no / little insulin is secreted, so glucose is not taken up by liver and muscle and converted to glycogen.
B1 B; B1 data quoted (higher peak / stays high); B1 lack of insulin so glucose not converted to glycogen.
(c) Rise in glucose detected by the pancreas; insulin secreted, causing liver and muscles to convert glucose to glycogen; this is negative feedback.
Q21Blood glucose control & diabetes · Challenge · Paper 4 style · 6 marks
Runners in a marathon in Lahore are running for more than three hours.
(a)During a long-distance run, blood glucose concentration begins to fall. Explain how the body brings it back to normal.[4]
(b)Suggest why adrenaline released at the start of the race also helps the runner.[2]
Show answer
(a) Fall detected by the pancreas; less insulin and more glucagon secreted; glucagon travels in the blood to the liver; liver converts glycogen to glucose, which enters the blood; glucose rises back towards the set point — negative feedback.
1 mark each, max 4: pancreas detects fall; glucagon secreted (insulin reduced); liver breaks down glycogen to glucose; glucose released into blood; negative feedback / returns to set point.
(b) Adrenaline raises blood glucose concentration (by glycogen breakdown) and increases heart rate, so more glucose and oxygen reach the muscles for respiration.
B1 increases blood glucose; B1 more glucose / oxygen delivered to muscles for respiration.
Q22Temperature control · Core · Paper 4 style · 5 marks
(a)State two ways the body responds when it is too hot.[2]
(b)State two ways the body responds when it is too cold.[2]
(c)Name the part of the brain that controls body temperature.[1]
Show answer
(a) Sweating; vasodilation (arterioles in the skin widen); (also less shivering / hair erector muscles relax).
1 mark each.
(b) Shivering; vasoconstriction (arterioles in the skin narrow); (also hairs raised).
1 mark each.
(c) Hypothalamus.
B1.
Q23Temperature control · Standard · Paper 4 style · 5 marks
(a)Explain how vasodilation helps a person to lose heat on a hot day.[3]
(b)Explain why the skin of a person looks pale when they are very cold.[2]
Show answer
(a) Arterioles supplying the skin capillaries widen (dilate); more blood flows near the skin surface; more heat is lost from the blood to the surroundings by radiation.
B1 arterioles dilate; B1 more blood to skin surface capillaries; B1 more heat lost (radiation / convection). Do not credit 'capillaries move'.
(b) Vasoconstriction: arterioles to the skin narrow, so less blood flows near the surface (reducing heat loss).
B1 arterioles constrict; B1 less blood near skin surface.
Q24Temperature control · Standard · Paper 4 style · 4 marks
(a)Explain how sweating cools the body.[2]
(b)Suggest why a person feels hotter in Karachi in humid monsoon weather than in Jacobabad in dry heat at the same air temperature.[2]
Show answer
(a) Water in sweat evaporates from the skin; evaporation uses heat energy from the skin, so the skin and blood are cooled.
B1 evaporation of water; B1 takes heat (energy) from the body.
(b) In humid air there is already a lot of water vapour, so sweat evaporates slowly; less heat is removed from the skin, so cooling is less effective.
B1 less evaporation in humid air; B1 so less heat lost / less cooling.
Q25Temperature control · Challenge · Paper 6 style · 7 marks
Three identical test-tubes each contain 20 cm³ of water at 80 °C. One has no covering, one is wrapped in one layer of cotton wool and one in three layers. The temperature is recorded after 10 minutes.Tube : temperature after 10 min / °Cno covering : 52one layer of cotton wool : 60three layers of cotton wool : 68
(a)Calculate the mean rate of cooling, in °C per minute, for each tube.[3]
(b)Explain how these results relate to the layer of fat under the skin of a seal living in cold water.[2]
(c)State two variables that should be kept constant.[2]
Show answer
(a) no covering: 2.8 °C/min; one layer of cotton wool: 2 °C/min; three layers of cotton wool: 1.2 °C/min
(80 − final temperature) ÷ 10 for each (M1); 2.8 and 2.0 (A1); 1.2 (A1).
(b) The covering acts as insulation, reducing heat loss — thicker layers cool more slowly; a thick fat layer under the skin insulates the seal and reduces heat loss to cold water.
B1 more layers = less heat loss / insulation; B1 fat acts as insulator in the animal.
(c) Any two of: starting temperature of water; volume of water; size / material of test-tube; room temperature; time interval.
1 mark each.
Q26Temperature control · Challenge · Paper 4 style · 6 marks
(a)Explain how the hypothalamus and negative feedback keep body temperature close to 37 °C when a person sits in a cold room.[4]
(b)Suggest why it is important that core body temperature stays close to 37 °C.[2]
Show answer
(a) Temperature receptors (in the hypothalamus / skin) detect a fall in blood temperature; hypothalamus sends nerve impulses to effectors; shivering (muscle contraction releases heat from respiration) and vasoconstriction (less heat lost); temperature rises back to the set point, then the responses stop — negative feedback.
1 mark each, max 4: receptors detect fall; hypothalamus coordinates / sends impulses; named effector response with explanation (shivering / vasoconstriction); return to set point / responses switched off = negative feedback.
(b) Enzymes work best at about 37 °C (optimum); too high and they denature, too low and reactions such as respiration are too slow.
B1 enzymes optimum; B1 denature at high / slow at low temperature.
Q27Synapses · Core · Paper 2 style · 1 mark
(a)What crosses the gap at a synapse?[1]
Show answer
(a) B neurotransmitter molecules
Neurotransmitter is released from vesicles and diffuses across the gap. The electrical impulse itself cannot jump the gap.
Q28Synapses · Standard · Paper 4 style · 4 marks
(a)Describe the sequence of events at a synapse after an impulse arrives at the end of the first neurone.[4]
Show answer
(a) Impulse arrives and vesicles move to the membrane; neurotransmitter is released into the synaptic gap; it diffuses across the gap; binds to receptor proteins on the next neurone, starting an impulse in it.
1 mark each: vesicles release neurotransmitter; into gap; diffuses across; binds to receptors → new impulse.
Q29Synapses · Challenge · Paper 4 style · 4 marks
(a)Explain why impulses can pass across a synapse in one direction only.[2]
(b)A drug has a shape similar to the neurotransmitter and binds permanently to the receptor proteins without starting an impulse. Suggest and explain the effect of the drug.[2]
Show answer
(a) Neurotransmitter is released only from vesicles in the first (pre-synaptic) neurone; receptor proteins are found only on the membrane of the second neurone.
B1 vesicles / neurotransmitter only on one side; B1 receptors only on the other side.
(b) Impulses are blocked / not passed on; the neurotransmitter cannot bind because the receptors are occupied, so no impulse is started in the second neurone.
Q30Homeostasis & negative feedback (general) · Standard · Paper 4 style · 4 marks
A thermostat in an air-conditioned office in Karachi switches the cooler on when the room rises above 24 °C and off when it falls back to 24 °C.
(a)Define homeostasis.[1]
(b)Using the thermostat in the office as a model, explain the principle of negative feedback in the body.[3]
Show answer
(a) The maintenance of a constant internal environment.
B1.
(b) A set point is maintained; a change away from the set point is detected (by receptors); a response (by effectors) reverses the change, returning it to the set point; once back at the set point the corrective response stops.
B1 set point; B1 change detected; B1 response opposes / reverses the change (and is switched off when normal).
Similar questions
Questions that test the same subtopic in different years, grouped so you can work on one skill at a time.
References only: find each question in its paper (official link where available, otherwise through your school).
Sense organs: the eyeBanker45 questions · 9/9 sessions
