Overview
What you’ll learn
- Trace a blood cell through both loops of the double circulatory system.
- Link each blood vessel’s layers and lumen to its pressure and job.
- Name every blood component and its function, including haemoglobin’s chemistry.
- Explain how fatty deposits cause coronary heart disease and evaluate stents vs statins.
- Interpret data linking diet, smoking, exercise and alcohol to non-communicable disease.
- Distinguish benign from malignant tumours and list the risk factors for cancer.
Specification checklist (AQA Trilogy 8464 · Edexcel 1SC0 · OCR Gateway J250)
Statements are paraphrased from the shared DfE combined science subject content and grouped by tier. Foundation content is studied by every student; Higher statements are examined on Higher-tier papers only. This chapter covers only what Combined Science (double award) examines — separate-science extras live on the GCSE Biology, Chemistry and Physics hubs. QuizQuip is not affiliated with AQA, Pearson Edexcel or OCR.
Foundation — every student
- 4.1Describe the heart as a double pump: the right side pumps deoxygenated blood to the lungs to collect oxygen, the left side pumps oxygenated blood around the body, and valves prevent backflow.
- 4.2Describe the structure and function of arteries, veins and capillaries, and explain how their structures suit their jobs, including how capillaries exchange substances with tissues.
- 4.3Describe blood as a tissue containing plasma, red blood cells, white blood cells and platelets, and explain the function of each component, including the transport of oxygen by haemoglobin.
- 4.4Describe coronary heart disease as the build-up of fatty material in the coronary arteries narrowing them and reducing blood flow to the heart muscle, and evaluate stents and statins as treatments.
- 4.5Describe health as the state of physical and mental wellbeing, explain how diseases can interact (for example immune reactions and physical mental health effects), and describe risk factors — including diet, smoking, exercise, alcohol and inherited factors — for non-communicable diseases, interpreting data on their effects.
- 4.6Describe cancer as the result of changes in cells leading to uncontrolled growth and division, distinguish benign tumours (contained in a membrane, not spreading) from malignant tumours (invading tissue and spreading), and link genetic and lifestyle risk factors — including smoking, alcohol, obesity, ionising radiation and viruses — to cancer risk.
- 4.7Calculate rates of blood flow and cardiac output from given data, and interpret graphs of disease incidence against lifestyle factors.
Key points
- 1Double circulatory system: right heart → lungs for oxygen; left heart → body; the left wall is thicker because it pumps further.
- 2Vessel ladder: arteries thick muscle, small lumen, high pressure · capillaries one cell thick for exchange · veins thin walls, valves, low pressure.
- 3Blood parts: plasma carries dissolved substances · red cells carry oxygen on haemoglobin (no nucleus, biconcave) · white cells defend · platelets clot.
- 4Coronary heart disease: fatty layers narrow the coronary arteries, starving heart muscle of oxygen — treated with stents (open the artery) or statins (lower blood cholesterol).
- 5Health = physical + mental wellbeing; diseases interact — immune problems invite others, and long illness weighs on mental health.
- 6Risk factors for non-communicable disease: diet, smoking, exercise level, alcohol, and inherited factors — read the correlation in the data, but remember correlation is not proof of cause.
- 7Cancer = uncontrolled cell growth and division; benign tumours stay in one place inside a membrane, malignant ones invade and spread.
- 8Cancer risk factors: smoking (lung), alcohol, obesity, ionising radiation, UV light, viruses (e.g. hepatitis), and inherited faulty genes.
Notes · 1 of 5
The double circulatory system
Two pumps in one muscle, two loops in one journey.
Your heart is one organ but two pumps. The right side sends deoxygenated blood a short hop to the lungs, where it dumps carbon dioxide and picks up oxygen. The left side then drives that oxygenated blood the long way round the whole body before it returns to the right side again. Because each circuit has its own pump, blood reaches the body at high pressure — the reason the left ventricle wall is the thickest muscle in the heart.
| Step | Where | Oxygen level |
|---|---|---|
| 1 | Body → right atrium (vena cava) | Low |
| 2 | Right atrium → right ventricle → pulmonary artery | Low |
| 3 | Lungs: carbon dioxide out, oxygen in | Rises |
| 4 | Pulmonary vein → left atrium → left ventricle | High |
| 5 | Aorta → body tissues | Falls as cells respire |
Worked example — cardiac output
Cardiac output = stroke volume × heart rate. A rower moves 70 cm³ per beat at 75 beats per minute: 70 × 75 = 5250 cm³ per minute = 5.25 dm³ per minute. During effort her rate rises to 150 bpm with a stroke volume of 160 cm³: 160 × 150 = 24 000 cm³ = 24 dm³ per minute — over four times the resting supply, which is how hard-working muscles get their oxygen.
Notes · 2 of 5
Blood vessels and blood
Three pipes, four components — each shaped for its job.
| Vessel | Structure | Job |
|---|---|---|
| Artery | Thick muscular wall, small lumen, high pressure | Carry blood away from the heart at pressure |
| Capillary | Wall one cell thick, tiny lumen, leaky | Exchange oxygen, nutrients and waste with tissues |
| Vein | Thin wall, large lumen, low pressure, valves | Return blood to the heart; valves stop backflow |
Blood itself is a tissue. Plasma — a pale yellow liquid — ferries dissolved glucose, amino acids, carbon dioxide, urea and hormones. Red blood cells are biconcave discs without a nucleus, packed with haemoglobin, which binds oxygen in the lungs and releases it where respiration is draining it. White blood cells come in two flavours: phagocytes that engulf microbes and lymphocytes that make antibodies. Platelets are cell fragments that trigger clotting at wounds.
Worked example — rate of blood flow
An artery carries 4800 cm³ of blood past a sensor in 4.0 minutes. Rate of flow = volume ÷ time = 4800 ÷ 4.0 = 1200 cm³ per minute. If the question asks for seconds: 1200 ÷ 60 = 20 cm³ per second. State the unit every time — the unit mark is real.
Notes · 3 of 5
Coronary heart disease: stents and statins
When the heart’s own supply narrows, and the two ways to widen the problem away.
The heart muscle has its own supply: the coronary arteries. In coronary heart disease, layers of fatty material build up inside them, narrowing the lumen. Less blood reaches the heart muscle, so it is starved of oxygen — causing chest pain and, if a deposit breaks loose, a heart attack. Two main treatments appear in exams:
| Treatment | What it does | Advantages | Drawbacks |
|---|---|---|---|
| Stent | A metal mesh inserted to hold the narrowed artery open | Works immediately; lowers the risk of a heart attack | Surgery carries risk; the artery can re-narrow; no effect on cholesterol elsewhere |
| Statins | Daily drugs that reduce cholesterol in the blood | Slows fatty build-up everywhere; proven to cut heart-attack risk | Must be taken long term; possible side effects such as muscle or liver problems; helps but does not clear existing deposits |
Evaluation questions want both sides: stents act fast but need an operation; statins are cheap and protective but demand lifelong tablets. Bypass surgery — replacing the narrowed section with a healthy vessel from elsewhere — is a third option worth naming.
Notes · 4 of 5
Health, disease interactions and risk factors
Wellbeing is more than the absence of infection — and diseases gang up.
Health is a state of physical and mental wellbeing, not merely an absence of disease. Diseases interact: a broken immune system invites other infections; a virus living in cells can trigger cancers; joint problems or severe illness depress mobility and mood. Non-communicable diseases — heart disease, many cancers, lung disease, diabetes — are not caught from anyone, but they do track lifestyle and environment:
| Factor | Linked to | Data the exam might give |
|---|---|---|
| Diet high in fat/salt/low in vegetables | Cardiovascular disease, some cancers | Death rates per 100 000 across countries |
| Smoking | Lung cancer, cardiovascular disease, lung disease | Incidence in smokers vs non-smokers over decades |
| Lack of exercise | Obesity, cardiovascular disease | Rates across activity levels |
| Alcohol | Liver disease, brain effects, harm to unborn babies | Units consumed vs liver diagnoses |
| Inherited factors | Some heart diseases and cancers | Family histories and gene studies |
Worked example — reading incidence data
A study of two groups of 40-year-olds finds lung cancer in 8 per 1000 heavy smokers but 1 per 1000 never-smokers over ten years. The incidence is 8 ÷ 1 = eight times higher among smokers — a strong correlation. What it does not prove, on its own, is causation: a causal claim needs the mechanism (carcinogens in smoke damaging DNA) and consistent evidence from many studies.
Notes · 5 of 5
Cancer: benign and malignant tumours
Uncontrolled division, two behaviours — and the risks you can and cannot change.
Cancer begins when changes (mutations) in a cell’s genes break the controls on growth and division. The cell and its descendants divide endlessly, forming a tumour. A benign tumour grows in one place, stays inside a membrane and does not invade neighbouring tissue — dangerous only by pressure. A malignant tumour invades surrounding tissue and sheds cells that travel in the blood or lymph to seed secondary tumours elsewhere — this spreading is what makes cancer life-threatening.
| Risk factor | Example cancers | Kind of factor |
|---|---|---|
| Smoking | Lung, mouth, throat | Lifestyle |
| Alcohol | Liver, bowel | Lifestyle |
| Obesity | Bowel, liver, kidney | Lifestyle |
| UV exposure | Skin | Environmental |
| Ionising radiation | Many | Environmental |
| Viruses living in cells | Liver (hepatitis), cervical (HPV) | Infection |
| Inherited faulty genes | Some breast and bowel cancers | Genetic |
Exam questions often ask you to separate the factors you can change (smoking, diet, alcohol, UV exposure) from the ones you cannot (inherited genes). Screening, vaccination against cancer-causing viruses, and not smoking are the standard risk-reducing answers.
Revise
Key terms
The words examiners expect you to use precisely.
- Double circulatory system
- Two loops — heart to lungs and heart to body — each served by its own pump.
- Haemoglobin
- The red pigment in red blood cells that binds oxygen in the lungs and releases it in tissues.
- Coronary arteries
- The arteries supplying the heart muscle itself; narrowed by fatty layers in coronary heart disease.
- Stent
- A metal mesh placed inside a narrowed artery to hold it open.
- Statins
- Drugs that lower blood cholesterol, slowing the build-up of fatty material.
- Non-communicable disease
- A disease that cannot be passed between people, such as heart disease or most cancers.
Show 1 more key termShow fewer key terms
- Malignant tumour
- A cancerous growth that invades nearby tissue and can spread to form secondary tumours.
Revise
Common mistakes
Where students most often lose marks in this chapter — and what to do instead.
Mistake: Saying the left side pumps blood to the lungs
That is the right side’s short loop.
Instead: Right heart → lungs; left heart → body.
Mistake: Giving veins thick muscular walls
Veins run at low pressure and need none.
Instead: Arteries are thick and muscular; veins are thin with valves.
Show 10 more mistakesShow fewer mistakes
Mistake: Saying red blood cells have a nucleus
Space is at a premium — the nucleus is lost as the cell matures.
Instead: Red cells have no nucleus, making room for more haemoglobin.
Mistake: Claiming plasma carries oxygen around the body
Almost all oxygen travels bound to haemoglobin.
Instead: Plasma carries dissolved foods, wastes, hormones and carbon dioxide; red cells carry oxygen.
Mistake: Describing coronary heart disease as a communicable disease
Nothing is caught from anyone.
Instead: It is non-communicable — lifestyle and inherited factors drive it.
Mistake: Saying statins unblock arteries immediately
Statins act slowly on blood cholesterol.
Instead: Stents open the artery at once; statins lower cholesterol over months and years.
Mistake: Writing “smoking causes cancer, full stop” from one graph
A single correlation does not prove cause.
Instead: Say the data shows a correlation; causation needs a mechanism plus wider evidence.
Mistake: Calling benign tumours cancerous
Benign growths stay put and do not spread.
Instead: Malignant = invading and spreading; benign = contained.
Mistake: Forgetting platelets are cell fragments
They are not whole cells.
Instead: Platelets are fragments that start clotting.
Mistake: Mixing up the pulmonary artery and pulmonary vein contents
Students assume arteries always carry oxygenated blood.
Instead: The pulmonary artery carries deoxygenated blood; the pulmonary vein carries oxygenated blood — the exception pair.
Mistake: Forgetting units in cardiac output
A bare number loses the unit mark.
Instead: Cardiac output in cm³ per minute (or convert to dm³ per minute).
Mistake: Saying cancer is a single disease with one cause
Cancers differ by tissue and risk profile.
Instead: Cancer describes uncontrolled division with many triggers — genetic, viral and lifestyle.
Check yourself
Quick quiz
20 questions with instant explanations. About 5 minutes.
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Explain the double circulatory system
Blood leaving the right ventricle travels next to the
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Practise
Topical questions
12 exam-style questions with model answers and mark schemes.
A set of structured and calculation questions matched to this chapter, in three tiers, each with a model answer, mark scheme and examiner tip. Higher-tier questions are tagged.
Practise topical questionsExam practice
Practice paper
A 30-mark paper in the style of a Combined Science paper, with a separate mark scheme. Give yourself 40 min.
Question paper
Chapter 4 Practice Paper
30 marks · 40 min · 6 pages
6 multiple-choice questions and structured questions with answer lines. Circulation and health: the double circulatory system, vessels, blood components, coronary heart disease treatments, risk factors for non-communicable disease, and cancer.
Mark scheme
PROChapter 4 Practice Paper — mark scheme
Answers · Marking points · 3 pages
Model answers with a mark for each creditworthy point — for marking at home or in class.
How does this chapter fit the real exams?
Biology Paper 1
1 h 15 · 70 marks (Trilogy)
Cell biology, organisation, infection and response, bioenergetics (chapters 1–7)
Biology Paper 2
1 h 15 · 70 marks (Trilogy)
Homeostasis, inheritance variation and evolution, ecology (chapters 8–10)
Tiers
Foundation (grades 1-1 to 5-5) · Higher (4-3 to 9-9)
Two grades are awarded together; the 21 required practicals are examined on the written papers
Want a full paper? Try the Biology Paper 1-style (Foundation), Biology Paper 1-style (Higher), Biology Paper 2-style (Foundation), Biology Paper 2-style (Higher), Chemistry Paper 1-style (Foundation), Chemistry Paper 1-style (Higher), Chemistry Paper 2-style (Foundation), Chemistry Paper 2-style (Higher), Physics Paper 1-style (Foundation), Physics Paper 1-style (Higher), Physics Paper 2-style (Foundation), Physics Paper 2-style (Higher), Required practicals practice sets.
Questions
Frequently asked questions
Is cancer covered in GCSE Combined Science?
Yes — benign and malignant tumours and the genetic and lifestyle risk factors for cancer are core Trilogy content in the DfE subject content shared by AQA Trilogy, Edexcel and OCR Gateway.
Which treatments do I need to know for coronary heart disease?
Stents (a mesh holding the artery open) and statins (drugs lowering cholesterol), with their advantages and disadvantages — and bypass surgery as a bonus. Evaluation questions want both sides.
What maths appears in this chapter?
Cardiac output = stroke volume × heart rate, rate of blood flow = volume ÷ time, unit conversion (cm³ to dm³), and percentage or ratio comparisons from incidence tables.
Why does the pulmonary artery carry deoxygenated blood?
Because “artery” means carrying blood away from the heart, not carrying oxygen. The pulmonary artery’s job is to take used blood to the lungs to be refreshed.
Do I need to memorise disease statistics?
No — the exam always supplies the data. You need the skill of describing the trend, calculating a ratio or percentage, and saying what the correlation does and does not prove.
Up next
Chapter 5: Plant transport systems