(a) Describe the features of ATP that make it suitable for its role as the universal energy currency of cells. [6] (b) Describe how you would carry out an investigation on the effect of temperature on the rate of respiration of yeast in anaerobic conditions using a redox indicator, such as methylene blue. [9]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

1. [1] small (molecule)
2. [1] water soluble so can move around cell
3. [1] immediate source of energy / immediate energy donor
4. [1] (can be) hydrolysed
5. [1] phosphate removed releases energy
6. [1] 30.5 kJ mol-1 (energy released per molecule)
7. [1] ATP splits to ADP and Pi
8. [1] reversible (reaction)
9. [1] intermediate between, anabolic and catabolic reactions / energy yielding and energy requiring reactions
10. [1] high turnover
11. [1] methylene blue / DCPIP, is a hydrogen acceptor (dye)
12. [1] becomes colourless when reduced
13. [1] use yeast suspension (in tube)
14. [1] add named sugar (solution) and, methylene blue / DCPIP
15. [1] put thin layer of oil on / put bung on, to prevent oxygen reaching yeast
16. [1] ref. to water bath (at set temperature)
17. [1] time how long it takes (for methylene blue / DCPIP) to go colourless
18. [1] use colorimeter (to measure colour change)
19. [1] ref. to 5 different temperatures
20. [1] repeat (whole) experiment at least twice more
21. [1] calculate mean values
22. [1] method to calculate rate of respiration; e.g. graph or 1 / T
23. [1] plot graph of rate of respiration against temperature