A-LevelBiologyEnzymesFeb/Mar 2017Paper 3 Q121 Marks
Enzyme E hydrolyses (breaks down) starch to reducing sugar. You are required to investigate the effect of temperature (independent variable) on the activity of E by recording the time taken for the starch to be hydrolysed (dependent variable). (a) You will investigate the hydrolysis of starch: • at room temperature • at other temperatures, starting at 40°C to a maximum of 80 °C. You are provided with: labelled | contents | hazard | volume/cm³ E | 2.0% enzyme E solution | harmful | 20 S | starch solution | none | 50 iodine | iodine solution | none | 15 You are advised to wear suitable eye protection. Iodine solution is a stain. If E or iodine comes into contact with your skin, wash it off immediately under cold water. The enzyme and starch solutions are mixed together and then a sample of the mixture is removed every 15 seconds and tested for starch. The end-point of the hydrolysis of the starch is when a sample does not change the colour of iodine solution, showing that all of the starch has been hydrolysed.
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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