Pearson Edexcel International GCSE (9–1) Human Biology UNIT: 4HB1 PAPER: 01. Latest 2022 revision paper. GradedA+

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Answer ALL questions. 1 The enzyme catalase is found in the liver. Catalase acts as a catalyst when added to hydrogen peroxide solution, causing the solution to break down into water and oxygen. A... student investigates the increase in the rate of breakdown of hydrogen peroxide into water and oxygen using catalase. This is the student’s method. • put 100 g of liver into 100 cm3 of water, and mix into a smooth paste • put 10 cm3 of the paste into a beaker at room temperature • add one drop of hydrogen peroxide to the paste • assess how many oxygen bubbles are produced on a scale of 0 to 5, with 5 representing most bubbles and 0 representing no bubbles The student repeats the investigation using different conditions. The conditions he uses are: • liver paste heated to 70 °C • liver paste that has been kept at 3 °C for an hour • acidified liver paste • liver paste with an alkali added • liver paste with no hydrogen peroxide added These are the student’s results. room temperature = 5 heated to 70°C = 0 kept at 3°C = 1 acid added = 2 alkali added = 3 no hydrogen peroxide added = 0 https://britishstudentroom-b430a.web.app/*P67060RRA0320* Turn over 3 (a) (i) Give the student’s results in the form of a suitable table. (3) (ii) State why this investigation is not reliable. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (iii) Give a reason why the results of this investigation are not accurate. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (iv) Describe how the investigation could be improved so that the conclusions could be more accurate and reliable. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... https://britishstudentroom-b430a.web.app/4 *P67060RRA0420* (b) (i) State the condition where the enzyme was most active. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) State the reason for including the beaker with no hydrogen peroxide added. (1) .................................................................................................................................................................................................................................................................................... (iii) Explain the result obtained when the conditions were acidic. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... 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