CAIE A-Level Biology 13.2.2 Effects of Photosynthesis Limiting Factors

Practise describing rate changes with comparative data, identifying optima or plateaus and switching the limiting-factor explanation when one variable no longer raises rate.

Exam points

describe rate changes and support each trend with comparative data and units
explain light or carbon-dioxide increases through added energy or substrate supply
explain temperature optima and declines through enzyme kinetics and denaturation

[Maximum number: 4]

(a)

Fig. 8.1 shows how the rate of uptake of carbon dioxide by a plant varies with temperature, at an optimum intensity of light on a clear day.
rate of uptake of carbon dioxide / arbitrary units (au)

Fig. 8.1

[ 4 ]

(i)

Suggest why the rate of carbon dioxide uptake levels off and then decreases after $20^{\circ} \mathrm{C}$ .

[ 3 ]

(ii)

On Fig. 8.1, draw a curve to show the uptake of carbon dioxide on a cloudy day.

[ 1 ]

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13.2.2—Effects of limiting factors question 1

Question (a)

Question (i)

Question (ii)