AQA A-Level Biology: Paper 1 2021 with complete solution

1.1 Describe the induced fit model of enzyme action and how an enzyme acts as a catalyst. - ans - The substrate binds to the active site and forms an ES complex. - The active site changes shape slightly so it's complimentary to the substrate. - This reduces the activation energy. 1.2 Tick one box to show which are the substrate the scientists must add to the reaction mixture is to produce ATP. - ans - Adenosine diphosphate. 1.3 Suggest and explain a procedure the scientist could have used to stop each reaction. - ans - The nature of the enzyme by putting it in ice. 1.4 Explain the change in ATP concentration with increasing inorganic phosphate concentration - ans - With increasing phosphate concentration more ES complex is form. - And at 40 mol dm3, all active sites are occupied. 2.1 Explain the advantage for large animals of having a specialised system that facilitates oxygen uptake. - ans - Large organisms have a smaller surface area to volume ratio.