A-LevelBiologyCell membranes and transport9700/12 · May/June 2016 · Q151 Mark
There is a high concentration of molecule X outside the cell which enters the cell by facilitated diffusion. The results of measuring the concentration of X inside the cell at 30s intervals are shown by the graph. [Figure 15.1] Why does the concentration of X inside the cell remain constant after 150 s? 1 There is no more of X outside the cell. 2 The number of carrier proteins is limiting. 3 There is no net movement of X.
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A1 and 2 only
B1 and 3 only
C2 and 3 only
D3 only
✓ Correct answer
D: 3 only
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