Biology 9700 · AS & A Level · Transport mechanisms

Transport mechanisms — practice question

Water is transferred from the soil solution into the xylem of roots through the apoplast and symplast pathways. Mineral ions can also be carried dissolved in water.
(a)[4]

Describe the movement of water from the soil solution to the endodermis of roots by the apoplast pathway and explain why this route stops at the endodermis.

(b)[3]

Researchers studied the transport mechanism used to take up potassium ions ($\text{K}^+$) into root epidermal cells at different concentrations of $\text{K}^+$ in the soil solution. Complete Table 6.1 by adding the information for the two transport mechanisms that the researchers identified.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Any four apoplast pathway features, for example passage through cell walls and intercellular spaces, stopping at the Casparian strip, the suberin barrier, or movement down a water potential gradient” …

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