Cotton, Gossypium hirsutum, and false flax, Camelina sativa, are crop plants that are grown in different parts of the world. Rubisco activase is an enzyme in the stroma of chloroplasts that is needed to maintain the activity of a second enzyme, rubisco. Scientists measured the activity of rubisco activase in cotton and in false flax at a range of temperatures. [Figure 2.1]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

1. [1] cotton (enzyme / rubisco activase) has a higher, optimum temperature / temperature at which activity is highest; ora
2. [1] maximum / highest / peak, activity higher in flax (enzyme / rubisco activase) (than in cotton); ora
3. [1] cotton (enzyme / rubisco activase) can work at higher temperature (than flax) ;
4. [1] (at stated temp) <30 °C flax (enzyme) has higher activity than cotton ; ora
5. [1] (at stated temp) >30 °C cotton (enzyme) has higher activity than flax ; ora
6. [1] (activity of) both increases then decreases as temperature increases ;
7. [1] (enzyme / rubisco activase) activity, same / 0.104 (au), at 30 °C;
8. [1] cotton, is adapted to / lives in areas with, high(er) temperatures ; ora
9. [1] ref. to different, genes / alleles (in cotton vs. flax);
10. [1] ref. to different primary structure of rubisco activase (in cotton vs. flax) ;
11. [1] ref. to different tertiary structure of rubisco activase (in cotton vs. flax) ;
12. [1] AVP;
13. [1] less / no, CO2 fixation / carboxylation of RuBP ;
14. [1] less / no, GP, made into / converted to, TP ;
15. [1] less / no, regeneration of RuBP ;
16. [1] less / no, glucose / hexose, made ;
17. [1] take, gene / (c)DNA, for rubisco activase ;
18. [1] from, cotton and insert into, (false) flax / (named crop) plant / embryo ;
19. [1] to maintain rubisco action at, high temperatures / >37.5 °C / up to 42.5 °C ;
20. [1] AVP;