Cardiovascular disease and its causes — Edexcel International A Level Biology
How atherosclerosis and blood clots lead to cardiovascular disease, the risk factors, dietary antioxidants, and Core practical 2 on vitamin C.
Revision notes
5 short notes, in the order of the specification. Each one in short:
Atherosclerosis is the build-up of fatty plaques (atheromas) in artery walls. It begins with damage to the endothelium, followed by an inflammatory response in which white blood cells take up cholesterol and a plaque forms. The artery narrows and stiffens, which raises blood pressure and causes further endothelial damage.
Blood clotting is a series of enzyme-controlled steps. Damaged tissue and platelets release thromboplastin, which catalyses the conversion of prothrombin to thrombin. Thrombin converts soluble fibrinogen to insoluble fibrin fibres that form a mesh trapping blood cells. A clot on a ruptured plaque can block an artery and cause a heart attack or stroke.
A risk factor raises the probability of developing CVD without guaranteeing it. Genetics, diet high in saturated fat and salt, increasing age, being male, high blood pressure, smoking and inactivity all increase risk, mainly by damaging the artery lining, raising LDL cholesterol or blood pressure, or making clots more likely. Several risk factors together raise the risk far more than any one alone.
Free radicals are highly reactive molecules that damage cells and oxidise LDL cholesterol, which promotes atherosclerosis. Dietary antioxidants such as vitamin C, vitamin E and carotenoids neutralise free radicals. Diets rich in fruit and vegetables are linked with lower CVD risk, but trials of antioxidant supplements have given conflicting results.
Vitamin C (ascorbic acid) reduces the blue dye DCPIP to a colourless form. Adding a food or drink extract to a fixed volume of DCPIP until it just turns colourless shows how much vitamin C it contains: a smaller volume needed means a higher concentration. Standards of known concentration give a calibration to calculate the unknown.
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9 exam-style questions (32 marks), each with its mark scheme.
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Quick check questions
Name the four stages in the course of events leading to atherosclerosis.
Show answer
Endothelial dysfunction, inflammatory response, plaque formation and raised blood pressure.
What does thrombin do?
Show answer
It is an enzyme that catalyses the conversion of soluble fibrinogen to insoluble fibrin.
Give two ways smoking raises the risk of CVD.
Show answer
Any two of: carbon monoxide reduces oxygen carried by haemoglobin; nicotine raises heart rate and blood pressure; chemicals damage the endothelium; platelets are stickier.
How do antioxidants reduce the risk of CVD?
Show answer
They neutralise free radicals, so less LDL is oxidised and there is less endothelial damage and foam cell formation.
In Core practical 2, what colour change shows vitamin C?
Show answer
Blue DCPIP turns colourless.
Frequently asked questions
What causes atherosclerosis?
Atherosclerosis starts with damage to the artery’s endothelium, for example from high blood pressure or smoking. LDL cholesterol enters the wall, white blood cells engulf it, and a plaque of cholesterol, cells and fibres forms. The artery narrows and stiffens, raising blood pressure and causing more damage.
How does a blood clot cause a heart attack?
If a plaque in a coronary artery ruptures, clotting starts and a thrombus forms in the narrowed artery. Blood flow to part of the cardiac muscle is blocked, so those cells lack oxygen, cannot respire aerobically and die. This is a myocardial infarction.
What are the risk factors for cardiovascular disease?
The risk factors are genetics, a diet high in saturated fat and salt, age, being male, high blood pressure, smoking and inactivity. They raise the probability of CVD by damaging the artery lining, raising LDL cholesterol or blood pressure, or making clots form more easily, and together they raise the risk further.
How do antioxidants protect against heart disease?
Antioxidants such as vitamin C and vitamin E neutralise free radicals, which would otherwise damage the endothelium and oxidise LDL cholesterol. Less oxidised LDL means fewer foam cells and less plaque. However, evidence from trials of antioxidant supplements is mixed, so the benefit is uncertain.
How do you test the vitamin C content of a drink?
Add the drink drop by drop to a fixed volume of blue DCPIP until it just turns colourless. Vitamin C reduces DCPIP, so the less drink needed, the more vitamin C it contains. Comparing with standards of known concentration lets you calculate the concentration.
Written and checked against the Edexcel International A Level Biology (YBI11) specification · Updated October 2026