A-LevelBiologyControl and coordination9700/42 · Oct/Nov 2017 · Q68 Marks

Cloves are the aromatic flower buds of the tree Syzygium aromaticum. Eugenol is a drug extracted from cloves. Eugenol affects the movement of sodium ions through the cell surface membranes of sensory neurones. (a) Fig. 6.1 shows the effect of eugenol concentration on the percentage decrease in sodium ion movement. [Figure 6.1]

(a)(i)Describe the effect of eugenol concentration on the percentage decrease in sodium ion movement.[2]
(a)(ii)Using Fig. 6.1, determine the percentage decrease in sodium ion movement at a eugenol concentration of 0.5mmol dm⁻³. percentage decrease ..................................................... %[1]
(b)Eugenol can be used to relieve the pain of toothache by putting it onto the affected tooth and gum. Suggest and explain how the action of eugenol may reduce pain.[5]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.

[2] 1 as the eugenol concentration increases the percentage decrease in sodium ion movement increases ; 2 percentage at two concentrations of eugenol plus units ;
[1] 57-58 (%);
[5] five from: 1 reduced entry of Na⁺ into sensory neurone ; 2 eugenol prevents opening of sodium ion channels / described ; 3 no / reduced, depolarisation of sensory neurone membrane ; 4 receptor potential / threshold potential, not reached ; 5 no / fewer, action potentials / impulses ; 6 may affect sodium-potassium pump ; 7 resting potential not restored ; 8 action potentials / impulses, do not reach brain ;

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.