A-LevelBiologyTransport in plants9700/41 · May/June 2022 · Q96 Marks

Stomata are involved in both transpiration and photosynthesis in plants. [Figure 9.1] Complete Table 9.1 by choosing the correct letter from Fig. 9.1 to match the feature stated in Table 9.1. Each letter may be used once, more than once or not at all. Table 9.1 letter feature location of Calvin cycle made mainly of cellulose

(a)Stomata are involved in both transpiration and photosynthesis in plants. [Figure 9.1] Complete Table 9.1 by choosing the correct letter from Fig. 9.1 to match the feature stated in Table 9.1. Each letter may be used once, more than once or not at all. Table 9.1 letter feature location of Calvin cycle made mainly of cellulose[2]
(b)The opening and closing of stomata are due to changes in environmental conditions. Hydrogen ions (H⁺) and potassium ions (K⁺) are involved in the opening of stomata. Describe how hydrogen ions and potassium ions are involved in the opening of a stoma.[4]

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Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

[1] (a) B location of Calvin cycle ;
[1] (a) D made of cellulose ;
[4] (b) any four from: 1 H+ pumped, out of guard cell / into cell wall of guard cell ; 2 inside of cell becomes (relatively) negatively charged ; 3 K+ enters cell by facilitated diffusion ; 4 water potential of cell decreases ; 5 water enters cell by osmosis ; 6 cell, expands / increases in volume / becomes turgid ; 7 stoma opens due to thick inner wall ;

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