Question 21N.2.SL.TZ0.3c
| Date | November 2021 | Marks available | [Maximum mark: 3] | Reference code | 21N.2.SL.TZ0.3c |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Explain | Question number | c | Adapted from | N/A |
The amount of food passing into food chains can be affected by the rate of photosynthesis. Explain the effect of one limiting factor on photosynthesis.
[3]
a. the rate of reaction will be limited by the limiting factor that is nearest to its minimum value;
temperature:
b. enzymes that control photosynthesis are influenced by temperature;
c. as temperature increases, reaction rate will increase;
d. above a certain temperature, the rate of photosynthesis will decrease;
e. (where temperature is limiting) essential enzymes begin to denature/not working to optimum;
light intensity:
f. light is source of energy / converted into chemical energy;
g. as light intensity increases reaction rate will increase;
h. at a certain light intensity, rate of photosynthesis will plateau;
i. another factor becomes limiting;
CO2 concentration:
j. CO2 is fixed to form organic molecules;
k. as CO2 concentration increases, reaction rate will increase;
l. at a certain concentration of CO2, rate of photosynthesis will plateau;
m. another factor becomes limiting;
Accept answers using an annotated graph to explain
Only accept the first factor described
Do not accept pH as a limiting factor
In 3c, most knew that temperature/CO2 concentration/light affect photosynthesis but could not explain the idea of acting as a limiting factor. Only the better students gained all 3 marks.
