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This paper covers the whole of Topic 9. Like a real Cambridge paper it ranges across every sub-topic — 9.1 circulatory systems, 9.2 the heart, 9.3 blood vessels and 9.4 blood — and it mixes them inside single questions. All three Topic 9 papers do; they differ in the angle they come at it from, not in what they cover.
Question 1 — Pushing the Pump, and Waiting for It to Come Back Down
Total: 12 marks
(a)[4]
Bela wants to find out how a period of physical activity changes her heart rate. She has a stopclock and a notebook and nothing else. Describe how she should carry out the investigation. Include how she measures her heart rate, one variable she must keep the same, and one thing she should do to make her results more reliable.
Model Answer — 1(a)
find the pulse by pressing two fingertips gently on an artery at the wrist or the side of the neck (not the thumb, which has a pulse of its own) [1]
count the beats for a measured time and convert — e.g. count for 15 s and multiply by 4, or 30 s and multiply by 2 — to give the rate in beats per minute [1]
keep one variable the same, e.g. the type and intensity of the exercise, the length of time she exercises for, the time of day, or the room temperature [1]
repeat the whole investigation on several days and take a mean, so that a single odd reading does not decide the result [1]
⚠ If you missed marks here: “Count her heartbeat” is not a method. The examiner wants a number produced in a stated unit, so the counting time and the multiplication are worth a mark on their own. And repeating a reading three times in the same minute is not a repeat of the investigation — the muscles are in a different state each time.
(b)(i)[3]
Fig. 1.1 shows the trace Bela recorded.State her resting heart rate, state the maximum heart rate she reached, and calculate the increase.
maximum heart rate = 150 beats per minute (accept 148–152) [1]
increase = 150 − 70 = 80 beats per minute [1]
⚠ If you missed marks here: The resting rate is the flat part before the shaded band, not the flat part after it — and the axis starts at 40, not at 0, so counting gridlines up from the bottom of the paper gives 30 too few. Always read the number printed on the axis.
(b)(ii)[2]
Bela stopped exercising at 14 minutes. Use Fig. 1.1 to work out how long her heart took to return to its resting rate after she stopped. State the reading you took from the graph.
Model Answer — 1(b)(ii)
the trace is back at 70 beats per minute at about 22 minutes (accept 21–23) [1]
recovery time = 22 − 14 = about 8 minutes [1]
⚠ If you missed marks here: Recovery time is measured from the moment exercise stops, not from the moment it starts. Reading 22 minutes off the graph and writing that as the answer throws away the subtraction mark. The fitter a person is, the shorter this time — which is why it is the number a coach actually cares about.
(c)[3]
While Bela is exercising her leg muscles take in more oxygen and glucose from the blood and release more carbon dioxide into it. Explain why her heart rate rises, and explain why it does not fall straight back to 70 the instant she stops.
Model Answer — 1(c)
a faster heart rate pumps a greater volume of blood per minute through the muscles [1]
so oxygen and glucose are delivered faster and carbon dioxide is carried away faster, keeping pace with the working muscles [1]
when she stops, the carbon dioxide that built up during exercise is still in the muscles and must be carried away, and the oxygen that was used up must be replaced, so the heart goes on beating quickly until the blood has cleared it [1]
⚠ If you missed marks here: “The heart speeds up to give the muscles energy” scores nothing. The heart does not make energy and does not deliver it — it delivers oxygen and glucose and removes carbon dioxide. Say what is being moved, and the mark is yours.
Question 2 — A Door That No Longer Shuts, and a Door That Barely Opens
Total: 12 marks
(a)[2]
Mr Fernandes is 58 and becomes breathless walking uphill. A scan shows that one of his valves no longer closes completely, so every time his left ventricle contracts, some blood is pushed backwards into the chamber behind it instead of leaving through the aorta. Name the valve that is failing, and state exactly where in the heart it is found.
Model Answer — 2(a)
the left atrioventricular valve (accept bicuspid or mitral valve) [1]
found between the left atrium and the left ventricle [1]
⚠ If you missed marks here: The clue is the word “backwards”. Blood is going back the way it came, so the guilty valve is behind the ventricle, not in front of it. A semilunar valve sits at the start of an artery, so a leaking semilunar valve would let blood fall back from the aorta — a different fault entirely. And Cambridge wants atrioventricular, never “flap”.
(b)[4]
Table 2.1 compares Mr Fernandes with a healthy adult of the same size, both at rest.
measurement (left side of the heart)
healthy adult
Mr Fernandes
volume of blood pushed out of the ventricle each beat / cm³
70
75
of that volume, the amount that goes backwards each beat / cm³
0
30
heart rate at rest / beats per minute
72
96
Calculate the volume of blood delivered to the body each minute in each case, showing your working, and explain why his resting heart rate is 96 and not 72.
Model Answer — 2(b)
healthy adult: 70 × 72 = 5040 cm³ per minute [1]
Mr Fernandes: only 75 − 30 = 45 cm³ actually leaves the heart each beat [1]
45 × 96 = 4320 cm³ per minute — about 14% less than the healthy adult, in spite of the faster heart [1]
his rate is higher because each beat delivers less blood, so the heart must beat more often to keep the volume delivered each minute as close to normal as it can [1]
⚠ If you missed marks here: The trap is 75 × 96. His ventricle really does push out 75 cm³, but 30 of it goes the wrong way, so only 45 reaches the body. Notice also that his ventricle is doing more work than the healthy one and achieving less — that is what makes a leaking valve so exhausting.
(c)[3]
A younger patient has the opposite kind of fault: the semilunar valve at the base of the pulmonary artery is narrowed, so blood has to be forced through a much smaller opening. State which chamber of the heart has to work harder, and explain the consequences of the narrowing.
Model Answer — 2(c)
the right ventricle [1]
it must contract more strongly to generate a higher pressure to force the same volume of blood through a narrower opening; over months and years its muscular wall becomes thicker [1]
less blood reaches the lungs in each beat, so less blood is oxygenated, and the patient becomes breathless when active [1]
⚠ If you missed marks here: Follow the blood, not the diagram. The pulmonary artery leaves the right ventricle, so it is the right side of the heart that is straining — even though the left ventricle is the thick-walled one in a healthy person. This question is also a neat demonstration of why the left ventricle is thick in the first place: a chamber thickens in response to the pressure it has to generate.
(d)[3]
Mr Fernandes has the faulty valve replaced with an artificial one. The artificial valve contains no muscle and no nerves, and nothing is connected to it, yet it works perfectly. Explain how a valve in the heart is opened and how it is closed, and state what a doctor with a stethoscope is actually listening to.
Model Answer — 2(d)
a valve is pushed open when the pressure of the blood behind it is greater than the pressure in front of it [1]
it is pushed shut when blood begins to flow backwards, filling the flaps or pockets so that they meet and seal the opening — so the valve is worked entirely by the blood itself, which is why an artificial one needs no muscle and no nerve supply [1]
the doctor is listening to the valves closing: the atrioventricular valves closing make the first sound and the semilunar valves closing make the second [1]
⚠ If you missed marks here: A very common wrong idea is that the heart, or the nervous system, decides when each valve opens. Nothing does. A valve is a passive one-way device that responds only to the pressure either side of it — and that is exactly why a lump of plastic and carbon can replace one. Note too that the sounds come from valves closing, not from blood rushing through or from muscle contracting.
Question 3 — Eight Hours Without Moving
Total: 12 marks
(a)[3]
Ravi is a security guard. He stands almost motionless for eight hours at a time. By the end of a shift his ankles are swollen and the veins on his lower legs stand out, bulging and twisted. Table 3.1 gives typical mean blood pressures measured at points around one systemic circuit.
position in the circuit
mean blood pressure / kPa
aorta
12.5
small artery in the leg
11.0
arteriole
6.0
capillary
3.0
small vein in the leg
1.2
vena cava
0.4
Describe how the blood pressure changes between the aorta and the vena cava, and explain what has caused the change.
Model Answer — 3(a)
the pressure falls all the way round, from 12.5 kPa in the aorta to 0.4 kPa in the vena cava — a fall of 12.1 kPa [1]
the largest fall is across the arterioles and capillaries: 11.0 kPa down to 3.0 kPa [1]
pressure is lost because the blood has to be forced through very narrow vessels, where there is a great deal of friction/resistance against the vessel walls, and the very large total cross-sectional area of the capillaries slows the blood down [1]
⚠ If you missed marks here: The pressure was not “used up by the heart” and the blood does not run out of energy. Pressure is lost as friction in narrow vessels — which is also why the low, steady pressure in the capillaries is a good thing: a wall one cell thick could not survive 12 kPa, and slow flow gives time for exchange.
(b)[3]
Blood in the veins of Ravi’s lower leg is at about 1 kPa and has to travel upwards, against gravity, all the way to the heart. Explain how it gets there.
Model Answer — 3(b)
veins have a thin wall and a wide lumen, and lie between the skeletal muscles of the leg [1]
when those muscles contract they squeeze the veins flat and press the blood along — the skeletal muscle pump [1]
valves spaced along the vein close as soon as blood starts to move backwards, so the squeezing can only push blood towards the heart — one-way flow [1]
⚠ If you missed marks here: Valves do not push. On their own they would leave the blood standing still in the leg for ever. The push comes from the skeletal muscles outside the vein; the valves only stop the push being wasted. An answer with valves but no muscles has no pump in it at all.
(c)[3]
Explain why eight hours of standing still makes Ravi’s ankles swell and the veins in his lower legs bulge and become twisted.
Model Answer — 3(c)
standing still means his leg muscles are hardly contracting, so there is almost no squeezing of the veins — the muscle pump is not working [1]
blood therefore collects in the veins of the lower leg under gravity, and the pressure inside them rises [1]
the thin walls stretch, so the valves are pulled apart and can no longer meet to seal the vessel; blood leaks backwards and pools, the veins swell and twist (varicose veins), and fluid is forced out of the capillaries into the tissues, swelling the ankles [1]
⚠ If you missed marks here: The valves do not “wear out” or break. They are perfectly good flaps that have simply been pulled too far apart to touch, because the wall they are attached to has been stretched. That is why the cure is compression stockings — narrow the vein again and the valves meet again.
(d)[3]
An artery runs down the same leg, carrying blood at more than eight times the pressure. It never bulges in this way and it contains no valves at all. Explain both of these observations.
Model Answer — 3(d)
blood in an artery is at high pressure because it has just been forced out of a contracting ventricle [1]
an artery has a thick wall containing muscle and elastic tissue and a relatively narrow lumen; the wall withstands the pressure without stretching permanently, and recoils between beats to keep the blood moving [1]
that pressure behind the blood is high enough that it never flows backwards, so no valves are needed [1]
⚠ If you missed marks here: Two classics to avoid. First, capillaries and arteries do not contain valves — only veins do (and the heart). Second, the reason veins have thin walls is not that “the blood has further to travel” but that there is almost no pressure left to contain. Wall thickness follows pressure, every time.
Question 4 — A Wall With a Gap In It
Total: 12 marks
(a)[2]
Fig. 4.1 shows the heart of a newborn baby who was born with a hole in one of its internal walls.Name structure S, and state its importance in a healthy heart.
Model Answer — 4(a)
S is the septum [1]
it keeps the oxygenated blood on the left side of the heart completely separate from the deoxygenated blood on the right side, so the two never mix [1]
⚠ If you missed marks here: Cambridge will not accept “pure” and “impure” blood, and “clean” and “dirty” are worse. The words are oxygenated and deoxygenated, and they are worth writing out every time. Note also that the septum is one wall, not two — it runs from between the atria all the way down between the ventricles.
(b)[4]
The pressure inside the left ventricle is far higher than the pressure inside the right ventricle. Use this fact and Fig. 4.1 to explain what happens each time the baby’s ventricles contract, and describe the effect on the right side of the heart.
Model Answer — 4(b)
blood is forced through the hole from the left ventricle into the right ventricle, because it moves from the higher pressure to the lower pressure [1]
so oxygenated blood is added to the deoxygenated blood already in the right ventricle [1]
that blood is then pumped along the pulmonary artery to the lungs for a second time, even though it is already oxygenated, which achieves nothing [1]
the right ventricle has to pump a larger volume with every beat, so it works much harder and its muscular wall becomes thicker [1]
⚠ If you missed marks here: Most people guess that blood crosses from right to left, because they are thinking about deoxygenated blood reaching the body. Blood does not choose a direction — it goes from high pressure to low pressure, and the left ventricle is the high-pressure chamber. The direction of flow through any hole is decided by the pressure, never by what the body needs.
(c)[3]
If the hole is very large, some deoxygenated blood crosses the other way as well, so the blood leaving the aorta is a mixture. Explain the effect of this on the tissues of the baby’s body.
Model Answer — 4(c)
the blood pumped into the aorta is a mixture, so each cm³ of it carries less oxygen than normal [1]
so less oxygen is delivered to the body cells; they cannot respire as quickly and less energy is released [1]
the baby tires very quickly — typically during feeding — grows slowly, breathes fast, and the lips and fingertips may look blue [1]
⚠ If you missed marks here: The volume of blood reaching the body is not reduced — the concentration of oxygen in it is. Getting that distinction right is the difference between a vague answer and a marked one. Notice how neatly this shows what the septum was for: remove it and the entire point of having two separate sides disappears.
(d)[3]
A fish has a single circulation. Explain the advantage of the double circulation of a mammal, and state what the hole in Fig. 4.1 does to that advantage.
Model Answer — 4(d)
in a fish the blood passes through the heart once per circuit; it loses most of its pressure squeezing through the narrow gill capillaries and then travels on to the rest of the body slowly [1]
in a mammal the blood returns to the heart after the lungs and is pumped a second time, so it leaves for the body at high pressure and flows quickly, delivering oxygen and glucose and removing carbon dioxide faster, which supports a much higher level of activity [1]
that advantage depends on the two circuits being completely separate; the hole joins them, so blood short-circuits between the sides and the separation — and much of the advantage — is lost [1]
⚠ If you missed marks here: “Double circulation” does not mean two hearts, and it does not mean twice as much blood. It means the blood passes through the one heart twice in every complete circuit — once on the way to the lungs, once on the way to the body. The advantage is pressure, and therefore speed of delivery.
Question 5 — Not Enough of One Element
Total: 10 marks
(a)[3]
Priya is 15. She has been feeling tired for months and her diet contains very little iron, which the body needs in order to make the protein that fills a red blood cell. Name that protein, name the substance it forms in the lungs, and describe what happens to that substance when the red blood cell reaches a respiring muscle.
Model Answer — 5(a)
the protein is haemoglobin [1]
in the lungs, where the oxygen concentration is high, haemoglobin combines with oxygen to form oxyhaemoglobin [1]
at a respiring muscle the oxygen concentration is low, so the oxyhaemoglobin breaks down again, releasing oxygen, which diffuses out of the red blood cell and into the muscle cells [1]
⚠ If you missed marks here: Haemoglobin and oxyhaemoglobin are two different words and Cambridge pays for both. The really important point is that the combination is reversible — if haemoglobin held on to oxygen permanently it would be useless. It picks up where oxygen is plentiful and lets go where oxygen is scarce, which is exactly where the oxygen is wanted.
(b)[4]
Describe two features of the structure of a red blood cell and explain how each one helps it to carry out its function.
Model Answer — 5(b)
biconcave disc shape [1]
— this gives a large surface area compared with its volume, and means no part of the inside is far from the surface, so oxygen diffuses in and out quickly [1]
no nucleus [1]
— this leaves more room inside the cell for haemoglobin, so each cell can carry more oxygen (also accept: the cell is small and flexible, so it can squeeze through a capillary in single file) [1]
⚠ If you missed marks here: A mature red blood cell has no nucleus — drawing one is one of the commonest errors in the whole of Biology, and it is the fastest way to tell a red cell from a white cell down a microscope. Notice also that each feature is worth a mark and each explanation is worth a separate mark, so listing four features without a single “because” scores two out of four.
(c)[3]
Table 5.1 shows Priya’s blood test results beside the normal values for a girl of her age.
measurement
normal value
Priya
haemoglobin / g per 100 cm³ of blood
13.5
8.4
red blood cells / million per mm³
4.6
3.5
mean volume of one red blood cell / µm³
90
71
white blood cells / thousand per mm³
7.0
6.8
Calculate the percentage by which Priya’s haemoglobin concentration is below the normal value, showing your working. Then explain why she is out of breath after climbing one flight of stairs.
with much less haemoglobin, each cm³ of her blood can carry less oxygen, so less oxygen is delivered to her muscles [1]
her muscles cannot respire fast enough to release the energy she needs for the stairs, so she breathes faster and her heart rate rises, trying to move the oxygen she does have round more quickly [1]
⚠ If you missed marks here: Read the table properly before you write. Her white blood cell count is essentially normal, so nothing here is an infection — and her cells are both fewer and smaller, which is exactly what a shortage of iron does. Watch the percentage too: 8.4 ÷ 13.5 × 100 = 62% is the percentage she has, not the percentage she is below.
Question 6 — Sealing the Hole, Then Defending It
Total: 12 marks
(a)[4]
Anjali cuts her hand deeply on a piece of broken glass. Within a few minutes the bleeding has stopped by itself. Describe how this happens. Name the two proteins involved and describe what the finished clot is made of.
Model Answer — 6(a)
platelets collect at the damaged surface and set off a series of reactions there [1]
the soluble protein fibrinogen, which is dissolved in the plasma, is converted into the insoluble protein fibrin [1]
the fibrin forms a mesh of fibres across the wound [1]
red blood cells and platelets are trapped in the mesh, forming the clot, which dries in the air to make a scab [1]
⚠ If you missed marks here: Fibrinogen and fibrin sound almost identical and are constantly written the wrong way round. Remember it by the ending: fibrinogengenerates fibrin. The other half of the mark is the word mesh — fibrin does not plug the hole by itself, it forms a net that catches the cells, and the cells are what actually block the gap.
(b)[2]
State the two roles of blood clotting.
Model Answer — 6(b)
it prevents further loss of blood [1]
it seals the wound so that pathogens cannot enter the body [1]
⚠ If you missed marks here: Almost everyone gets the first role and forgets the second. A clot is a barrier as well as a plug — it is part of the body’s defence, not only part of its plumbing. Two marks means Cambridge wants two clearly different ideas, so “stops bleeding and stops blood loss” is one mark, twice.
(c)[4]
Bacteria got into the cut before the clot formed. Name the two types of white blood cell that deal with them, and describe what each one does.
Model Answer — 6(c)
phagocytes — recognisable by a lobed nucleus and a grainy cytoplasm [1]
they engulf the bacteria and digest them; this process is called phagocytosis [1]
lymphocytes — recognisable by a very large round nucleus filling almost the whole cell [1]
they produce antibodies, proteins that attach to the bacteria and either destroy them directly or mark them so that phagocytes destroy them [1]
⚠ If you missed marks here: “White blood cells eat germs” earns nothing at all: the word is phagocytosis, the cell is a phagocyte, and the invaders are pathogens. And do not confuse white blood cells with platelets — platelets are cell fragments that deal with clotting and have nothing to do with attacking bacteria.
(d)[2]
Rather more than half of blood is not cells at all. Name this part of the blood, and list four things other than blood cells that it transports.
Model Answer — 6(d)
plasma [1]
any four of: ions, nutrients (glucose, amino acids), urea, hormones, carbon dioxide, heat [1]
⚠ If you missed marks here: Oxygen is the one thing on everybody’s list that does not belong here — almost all of it is carried by haemoglobin inside the red blood cells, not by the plasma. Urea is the one everybody forgets, and plasma carries the blood cells themselves too, which is why the question had to say “other than blood cells”.
Question 7 — The Pump That Cannot Feed Itself
Total: 10 marks
(a)[2]
State what the coronary arteries supply, and name the two substances that must reach the heart muscle continuously.
Model Answer — 7(a)
they supply the muscular wall of the heart itself with blood, branching over its surface from the base of the aorta [1]
oxygen and glucose (accept nutrients) [1]
⚠ If you missed marks here: “They supply the heart” is too loose to mark. Say the wall, or the muscle, of the heart — the point is that heart muscle is tissue like any other and cannot survive on the blood rushing past it inside the chambers.
(b)[3]
Fig. 7.1 shows cross-sections through two coronary arteries drawn to the same scale.Calculate the percentage by which the lumen diameter of artery B is smaller than that of artery A, showing your working. Then explain why the man gets chest pain when he climbs stairs but has none while he is sitting down.
far less blood can flow through the narrowed artery, so less oxygen and glucose reach that part of the heart muscle [1]
while he is sitting the reduced supply is just enough; climbing stairs makes his heart beat faster and more strongly, so the muscle needs more oxygen than the narrowed artery can deliver, and the shortage is felt as pain [1]
⚠ If you missed marks here: The artery is not blocked, so the “why only on the stairs” mark is about demand, not supply: nothing changed in the artery, everything changed in the muscle. Watch the calculation as well — 1.2 ÷ 3.0 × 100 = 40% is the percentage that remains, so the reduction is 60%.
(c)[3]
Describe how a change of diet and a change in the amount of exercise he takes could each reduce his risk of the artery becoming completely blocked.
Model Answer — 7(c)
diet: eat less saturated (animal) fat and cholesterol, and less salt [1]
because fatty material is deposited in the artery wall and narrows the lumen further, and less salt helps to lower the blood pressure, which reduces damage to the artery lining [1]
exercise: take regular exercise — it strengthens the heart muscle, lowers blood pressure and resting heart rate, and helps to keep body mass down, all of which reduce the risk [1]
⚠ If you missed marks here: “Eat healthily and exercise more” is worth nothing. Name the change — less saturated fat, less salt — and then say what it does to the artery. Remember too that diet and exercise are only two of the risk factors: age, sex, stress, smoking and genetic predisposition also count, and the first two of those cannot be changed at all.
(d)[2]
State two ways in which the activity of a person’s heart may be monitored, and for each one state what is being measured or heard.
Model Answer — 7(d)
an ECG (electrocardiogram), which records the electrical activity of the heart as it beats [1]
any one of: measuring the pulse rate at an artery, which counts the surges of pressure produced by each ventricular contraction; or listening through a stethoscope to the sounds of the valves closing [1]
⚠ If you missed marks here: Cambridge lists exactly three methods — ECG, pulse rate, and listening to the valves closing — so learn them as a set of three. Note also that a pulse can only be felt in an artery: by the time the blood reaches a vein the pressure surges have been smoothed away entirely, as Table 3.1 showed.
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