Biology as Revision

Topics: DNA, Cell, Gene Pages: 25 (6686 words) Published: February 24, 2013
Salters Nuffield Advanced Biology

AS Revision summary
Unit 1 Topic 1: Lifestyle, health and risk Topic 2: Genes and health Unit 2 Topic 3: Topic 4:

SNAB Biology AS Revision Summary

Understanding the specification
The following summary tries to explain what is meant by the specification statements for the SNAB AS course. SNAB includes a lot of material because it helps you to understand ideas or because it is interesting, but it can be a little confusing when it comes to knowing what to revise. This brief summary will not help you to understand the biology and it is not intended to replace a revision programme, but it might help to sort the wood from the trees a little. Remember that examination questions must be set so that you could do them with no reference to the SNAB course materials. Only the statements in bold below can be examined. You will not, for example be asked questions that expect you to recall the ‘Nice to Know’ information in the book, but it might help if you understand it. About half of the examination questions will expect you to recall facts, with the other half asking you to show that you understand ideas. You will often be given unfamiliar material and asked to suggest what might be going on by using ideas that you have studied. Numbers in brackets are page references to the SNAB text books so that you can read more fully if one of the statements isn’t completely clear.


SNAB Biology AS Revision Summary

SNAB Biology – Unit 1 revision outline Topic 1: Lifestyle, health and risk 1.1.1 Explain why many animals have a heart and circulation (mass transport to overcome limitations of diffusion)  Large and multicellular means small SA:vol ratio (54)  Cells can be specialised (6) Explain how the structures of blood capillaries, arteries and veins relate to their functions  Capillaries – small, wall single cell thick. Rapid diffusion, leaky for tissue fluid formation (9)  Arteries. – narrow lumen, thick walls (collagen, elastic fibres, smooth muscle), no valves (8). Stretch during systole, maintain high pressure (9)  Veins – wide lumen, thin walls (less collagen, few elastic fibres, little muscle), valves (8). Low pressure, valves prevent back flow, flow due to skeletal muscle contraction and low pressure in thorax (9). Relate the structure and operation of the mammalian heart to its function (the cardiac cycle including diastole, atrial systole and ventricular systole)  Diastole – muscle at rest, semi lunar valves prevent back flow, blood entering from veins into atria and ventricles due to elastic recoil of heart, atrio ventricular valves open.  Atrial systole – atrial muscle contracts, blood fills ventricles.  Ventricular systole – ventricular muscle contracts, pressure closes atrio ventricular valves and opens semi lunar valves.  Thickness of chamber walls related to function (10-11). Explain the course of events that leads to atherosclerosis (endothelial damage, inflammatory response, plaque formation, raised blood pressure)  Fatty deposits (plaques) narrowing and hardening arteries. Increases risk of blockage by blood clots, restricts blood flow.  Damaged endothelial cells due to high BP or toxins (eg from cigarettes).  Inflammatory response – WBC accumulate and collect cholesterol to form atheroma.  Calcium salts and fibrous tissue added to form plaque.  BP increases – positive feedback (11).





SNAB Biology AS Revision Summary


Describe the blood clotting process (thromboplastin release, conversion of prothrombin to thrombin and fibrinogen to fibrin) and its role in CVD  Thromboplastin released from platelets and damaged tissue.  Converts prothrombin to thrombin.  Converts fibrinogen to fibrin, which makes clots form (13). Describe the symptoms of CVD, ie coronary heart disease (CHD) and stroke, and the factors which increase the risk of CVD (genetic, diet, age, gender, high blood pressure, smoking and inactivity) ...
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