Cardiovascular disease and its causes: exam questions

Answer: B – damage to the endothelium of the artery

• damage to the endothelium / endothelial dysfunction (1)
• LDL cholesterol enters the artery wall (1)
• inflammatory response: white blood cells / monocytes / macrophages enter and take up cholesterol (1)
• plaque / atheroma forms from cholesterol, foam cells, fibres and calcium (1)
• lumen narrows and wall loses elasticity (1)
• blood pressure rises, causing further endothelial damage (1)
• Max 5

• platelets / damaged tissue release thromboplastin (1)
• thromboplastin catalyses conversion of prothrombin to thrombin (1)
• thrombin catalyses conversion of soluble fibrinogen to insoluble fibrin (1)
• fibrin forms a mesh of fibres that traps blood cells / platelets, forming a clot (1)
• Max 4

• plaque may rupture / lumen is narrowed (1)
• clotting is triggered / a thrombus forms on the plaque (1)
• artery blocked / blood flow to part of the cardiac muscle stops (1)
• cardiac muscle cells do not receive oxygen / glucose, so cannot respire aerobically and die (1)
• Max 4

• carbon monoxide binds to haemoglobin, reducing oxygen transport / oxygen supply to heart muscle (1)
• nicotine increases heart rate / blood pressure (1)
• chemicals in smoke damage the endothelium, leading to atherosclerosis (1)
• platelets become stickier / clotting more likely (1)
• Max 3

Answer: A – by neutralising free radicals that oxidise LDL

• people who eat fruit and vegetables may also exercise more / smoke less / eat less saturated fat (1)
• so the lower risk may not be caused by antioxidants (correlation is not causation) (1)
• fruit and vegetables contain other beneficial substances, such as fibre, or antioxidants work in combination (1)
• tablets may give the wrong dose / form / the trials may have been too short (1)
• Max 3

• add a fixed volume of DCPIP (blue) to a test tube (1)
• add the juice drop by drop from a graduated pipette / burette, shaking, until the blue colour just disappears (1)
• record the volume of juice needed; repeat and calculate a mean (1)
• repeat with the stored juice (1)
• the juice needing the smaller volume contains more vitamin C (1)
• control volume and concentration of DCPIP, temperature and the rate of adding juice (1)
• wear eye protection / wipe up spills of DCPIP (1)
• Max 5

• (i) fresh mean = (1.5 + 1.6 + 1.4) ÷ 3 = 1.5 cm³ (1)
• boiled mean = (2.0 + 2.1 + 1.9) ÷ 3 = 2.0 cm³ (1)
• (ii) vitamin C needed = 0.6 cm³ × 1.0 mg cm⁻³ = 0.6 mg (1)
• fresh 0.6 ÷ 1.5 = 0.40 mg cm⁻³; boiled 0.6 ÷ 2.0 = 0.30 mg cm⁻³ (1)
• (iii) (0.30 − 0.40) ÷ 0.40 × 100 = −25 % (1)
• (iv) vitamin C is destroyed / oxidised by heating (1)