WJEC Biology for A2 Level: Revision Workbook

Understanding AO2: Applying knowledge and understanding You will need to apply knowledge and understanding of scientific ideas, processes, techniques and procedures: ⦁ In a theoretical context ⦁ In a practical context ⦁ When handling qualitative data (this is data with no numerical value, e.g. a colour change) ⦁ When handling quantitative data (this is data with a numerical value, e.g. mass/g). 45% of the available marks on the A2 exam papers are for application of knowledge and understanding. Common command words used here are: describe (if it’s unfamiliar data or diagrams), explain and suggest. AO2 tests applying ideas, processes, techniques and procedures detailed in the specification to unfamiliar situations including using mathematical calculations and interpreting the results of statistical tests. If you were asked to describe the effects of a weed-killer on non-cyclic photophosphorylation explaining why cyclic photophosphorylation was unaffected given the information that the weed-killer blocks electron flow from Photosystem II to the electron carrier, you might write: ‘It stops electrons moving out of Photosystem II into the electron carrier so electrons can’t pass to Photosystem I.’ This is an incomplete answer and does not explain why cyclic photophosphorylation is unaffected. A good answer would say: ‘The weed-killer stops electrons from Photosystem II being moved to Photosystem I, which prevents the reduction of NADP to reduced NADP. Photolysis of water cannot occur. Cyclic photophosphorylation is not stopped because the electrons are still able to pass from Photosystem I and return back to Photosystem I.’ Describing data It is important to describe accurately what you see, and to quote data in your answer. If you were asked to compare the volume of juice produced when using enzymes bound to the gel membrane surface compared to the enzyme immobilised inside the beads, you might write: ‘The volume of juice extracted increases with temperature up to the optimum temperature of 60°C in both enzymes. Above this, the volume of juice decreases.’ This is a basic answer. A good answer needs to be both accurate and detailed. For example: ‘Increasing temperature causes the volume of fruit juice extracted to increase up to 60°C. The volume of juice collected is higher up to 60°C with the enzyme bound to the gel membrane, peaking at 95 cm 3 compared to 75 cm 3 for the enzyme immobilised inside the beads. Above 60°C the volume of fruit juice extracted decreases, but this is more noticeable for the enzymes bound to the gel membrane surface which decrease by 40 cm 3 compared to just 10 cm 3 for the enzyme immobilised inside the beads.’ If you were also asked to explain the results, a basic answer would include reference to ‘ increased kinetic energy up to 60°C, and denaturing enzymes above 60°C’ . A good answer is one that uses detailed biological terminology accurately and has clarity and coherence. A good answer would also include reference to ‘ increased enzyme– substrate complexes forming up to 60°C’ and would include that ‘ above 60°C, hydrogen bonds break, resulting in the active site changing shape so fewer enzyme–substrate complexes could form ’ . 0 1 0 20 20 3 0 40 50 60 7 0 3 0 40 50 60 7 0 8 0 9 0 1 0 0 temperature / º C F ree enz ymes E nz yme b ound to gel memb rane surface E nz yme immob ilised inside b eads volume of fruit j uice extracted / cm 3 0 1 0 20 20 3 0 40 50 60 7 0 3 0 40 50 60 7 0 8 0 9 0 1 0 0 temperature / º C F ree enz ymes E nz yme b ound to gel memb rane surface E nz yme immob ilised inside b eads volume of fruit j uice extracted / cm 3 6 | WJEC Biology for A2 Level: Revision Workbook | Introduction Copyright: Sample material