AS BIOLOGY 7401/1 Paper 1 Mark scheme June 2021

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AS BIOLOGY 7401/1 Paper 1 Mark scheme June 2021 1. Substrate binds to the active site/enzyme OR Enzyme-substrate complex forms; 2. Active site changes shape (slightly) so it is complementary to s... ubstrate OR Active site changes shape (slightly) so distorting/breaking/forming bonds in the substrate; 3. Reduces activation energy; 3 1. Accept for ‘binds’, fits Question Marking Guidance Mark Comments 01.2 Adenosine diphosphate; 1 Question Marking Guidance Mark Comments 01.3 Mark in pairs, 1 and 2 OR 3 and 4 OR 5 and 6 1. Boil OR Add (strong) acid/alkali; 2. Denatures the enzyme/ATP synthase; OR 3. Put in ice/fridge/freezer; 4. Lower kinetic energy so no enzyme-substrate complexes form; OR 5. Add high concentration of inhibitor; 6. Enzyme-substrate complexes do not form; 2 1. Accept heat at > 50oC OR at very high temperatures 2. Accept for 'denatures', a description of denaturation 4. Accept ES for enzyme substrate complex MARK SCHEME – A-LEVEL BIOLOGY – 7402/1 – JUNE 2021 6 Question Marking Guidance Mark Comments 01.4 1. (With) increasing Pi concentration, more enzyme-substrate complexes are formed; 2. At or above 40 (mmol dm-3 ) all active sites occupied OR At or above 40 (mmol dm-3 ) enzyme concentration is a limiting factor; [Show More]

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