O-LevelBiologyPlant Nutrition5090/22 · May/June 2023 · Q610 Marks

Fig. 6.1 shows the pattern of results from an investigation into the effect of increasing light intensity on the rate of photosynthesis. [Figure 6.1]

(a)Describe and explain the pattern of results between a light intensity of 20 and 30 arbitrary units.[2]
(b)(i)The investigation was repeated with an increased concentration of carbon dioxide in the atmosphere. Draw a curve on Fig. 6.1 to show the pattern of results that would be expected from this second investigation.[2]
(b)(ii)State the name of the product of photosynthesis that contains carbon atoms.[1]
(b)(iii)Outline the uses made by a plant of named carbohydrates.[5]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[2] constant AW + rate ; light + not a limiting factor ;
[2] from 0,0 + line gradient same up to at least light intensity 5; ends at light intensity = 30 + levels out higher + after light intensity = 19;
[1] glucose;
[5] 1 glucose + respiration ; 2 respiration / glucose + releases energy / ATP ; 3 starch + store ; 4 glucose + used to make amino acids / proteins / lipids ; 5 cellulose + cell walls; 6 sucrose + transport;

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