Biology 9700 · AS & A Level · Transport mechanisms

Transport mechanisms — practice question

Table 1.1 presents three of the ways in which dissolved substances can cross cell membranes. It also gives five statements that may or may not describe each of these three processes. Fill in Table 1.1 to indicate which statements apply to each of the three processes shown. Put a tick (✓) where a statement applies, or a cross (✗) where it does not. Every box must contain either a tick or a cross. The first row has already been completed.
(a)[4]

Complete Table 1.1 to show which statements apply to active transport, facilitated diffusion and simple diffusion.

(b(i))[1]

On Fig. 1.1, draw a label line and use the letter C to identify the Casparian strip.

(b(ii))[1]

Root hairs are about $5\,\mu\text{m}$ across and $500\,\mu\text{m}$ long. Explain how this makes them suitable for water absorption.

(b(iii))[1]

Name the pathway followed by the water shown by the arrows in Fig. 1.1.

(c)[3]

Water enters the xylem vessels shown in Fig. 1.1. Explain how water rises through the xylem vessels to the leaves as a continuous column.

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This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Oxygen entering a red blood cell occurs by simple diffusion” …

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