24 8 Yeast is a single-celled organism that can respire aerobically. Mitochondria are the sites of aerobic respiration in yeast cells. (a) The diagram shows a mitochondrion. P R Q S (i) Which labelled component in the diagram is the site of the Krebs cycle? (1) A P B Q C R D S (ii) Which labelled component in the diagram is the site of oxidative phosphorylation? (1) A P B Q C R D S (iii) Yeast cells can have many small mitochondria. Calculate the magnification of the diagram if the maximum length of the mitochondrion is 0.5 µm. (2) Answer .............................................................. Turn over 25 (b) (i) Name two molecules needed for aerobic respiration that can move into the mitochondria. (2) 1 ................................................................................................................................................................................................................................................................................ 2 ................................................................................................................................................................................................................................................................................ (ii) The outer mitochondrial membrane is not permeable to hydrogen ions (H+). Explain the importance of this feature of the membrane. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 26 (c) It has been stated that if the temperature of yeast is raised by 10 °C, the rate of respiration will double. The diagram shows some apparatus that can be used to measure the rate of respiration in yeast. scale (mm) clip potassium hydroxide solution coloured liquid yeast suspension 200 180 160 140 120 100 80 60 40 20 0 Devise an investigation using this apparatus to determine whether an increase of 10 °C doubles the rate of respiration in yeast. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 8 = 14 marks) Turn over 27 BLANK PAGE