A student investigated the effect of temperature on the rate of photosynthesis at two different light intensities. The rate of photosynthesis was determined by measuring the rate of oxygen production of the plant. [Figure 7.1] shows the result of the investigation.

Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

1. [3] (a)(i) 1 rate of oxygen produced / rate of photosynthesis, is low / stays constant or small decrease in, rate of oxygen produced / rate of photosynthesis ;
2. [3] (a)(i) 2 light intensity was the limiting factor / AW ;
3. [3] (a)(i) 3 (so) less / little, light energy absorbed / photolysis (of water) / photoactivation (of chlorophyll)/ light-dependent reactions / photophosphorylation ; R no light energy absorbed
4. [3] (a)(ii) any three from:
5. [3] (a)(ii) 1 rate of oxygen produced / rate of photosynthesis, decreased ;
6. [3] (a)(ii) 2 two paired data quotes with units ;
7. [3] (a)(ii) temperature / °C | rate of oxygen production / mm³ h-1
8. [3] (a)(ii) 30 | 4 / 4.00
9. [3] (a)(ii) 40 | 2.55
10. [3] (a)(ii) 50 | 0.65 (A 0.62-0.65)
11. [3] (a)(ii) 3 because, enzyme / ATP synthase / NADP reductase / oxygen evolving complex, denatured ; A rubisco
12. [3] (a)(ii) 4 change in active site / fewer ESCs ;
13. [3] (b) any three from:
14. [3] (b) 1 light absorbed by, photosystem II / P680 or photoactivation / photoionisation (of chlorophyll) ;
15. [3] (b) 2 photolysis (of water) ;
16. [3] (b) 3 water-splitting enzyme / oxygen evolving complex ;
17. [3] (b) 4 water splits into protons, electrons and oxygen ; A equation