24 8 Cysteine proteases are enzymes found in fruits such as pineapples. When a protease enzyme is added to fat‑free skimmed milk, the milk turns from cloudy to clear. (a) Devise an investigation to find the optimum temperature for the activity of the enzyme cysteine protease found in pineapples. (6) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... Turn over 25 (b) Cysteine proteases are also found in the predatory bacterium Bdellovibrio bacteriovorus (BvB). These bacteria are harmless to humans but prey on Gram negative bacteria. (i) Give two differences between Gram negative and Gram positive bacteria. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) The cell of the predatory BvB is 1µm in length and can swim 100 times its length per second. Calculate the swimming speed of this bacterial cell in mm s–1. (2) Answer .............................................................. 26 (iii) The BvB bacteria have been described as ‘living antibiotics’. Explain why the BvB bacteria might be useful in the future for treating bacterial infections. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 8 = 12 marks) Turn over 27 BLANK PAGE