Edexcel A Level Biology A Topic 1: Lifestyle, Health and Risk Exam Questions

About Edexcel A Level Biology A Topic 1: Lifestyle, Health and Risk

Topic 1 of Edexcel A Level Biology A (Salters-Nuffield) uses cardiovascular disease (CVD) as the context for learning core biology. You study why large animals need a circulatory system, the dipolar nature of water, the structure of the heart and blood vessels, the cardiac cycle, atherosclerosis and the blood clotting cascade. The biochemistry of carbohydrates and lipids is linked to diet, energy budgets and obesity indicators such as BMI and waist-to-hip ratio. You also evaluate risk factors, treatments for CVD and how people perceive risk. Core practicals on vitamin C content and the effect of caffeine on Daphnia heart rate are regularly examined.

What you need to know

• Water and circulation Water is a dipole, so it is a good solvent for transport in blood. Large multicellular animals need a mass transport system because their surface area to volume ratio is small.
• Heart and cardiac cycle Know the stages of atrial systole, ventricular systole and diastole, the pressure changes that open and close atrioventricular and semilunar valves, and how artery and vein structure relates to function.
• Atherosclerosis and clotting Endothelial damage leads to an inflammatory response, build-up of cholesterol, fibres and dead cells (plaque) and narrowing of arteries. Clotting: thromboplastin activates the conversion of prothrombin to thrombin, which converts soluble fibrinogen into insoluble fibrin.
• Carbohydrates and lipids Monosaccharides join by glycosidic bonds in condensation reactions to form disaccharides and polysaccharides (amylose, amylopectin, glycogen). Triglycerides form by ester bonds between glycerol and three fatty acids; saturated fatty acids have no C=C double bonds.
• Risk factors and treatments Risk factors include genetics, age, sex, high blood pressure, smoking, inactivity, and diets high in saturated fat and salt. Treatments include antihypertensives, statins, anticoagulants and platelet inhibitors, each with risks and benefits.
• Core practicals Use DCPIP titration to compare the vitamin C content of fruit juices, and investigate the effect of caffeine on Daphnia heart rate while considering the ethics of using invertebrates.

Common mistakes in Topic 1: Lifestyle, Health and Risk

• Saying atherosclerosis is caused only by eating fat; it starts with damage to the endothelium followed by an inflammatory response.
• Confusing thrombin with thromboplastin; thromboplastin is released from platelets and damaged tissue, thrombin is the enzyme that converts fibrinogen to fibrin.
• Stating that correlation proves causation in CVD studies; a correlation suggests a link but does not prove one factor causes another.
• Writing that HDLs and LDLs are both harmful; high LDL levels are linked to plaque formation while HDLs carry cholesterol to the liver.
• Mixing up valves: atrioventricular valves close when ventricular pressure exceeds atrial pressure, semilunar valves open when it exceeds arterial pressure.

Try three Topic 1: Lifestyle, Health and Risk exam-style questions