DP Biology (first assessment 2025)

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Question 21M.1A.SL.TZ2.4

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Date May 2021 Marks available [Maximum mark: 1] Reference code 21M.1A.SL.TZ2.4
Level SL Paper 1A Time zone TZ2
Command term Question number 4 Adapted from N/A
4.
[Maximum mark: 1]
21M.1A.SL.TZ2.4

Which graph best represents the relationship between the concentration of chloride ions in the external environment of a cell and the rate at which the chloride ions move by facilitated diffusion into the cytoplasm of the cell?

[1]

Markscheme

C

Examiners report

It was expected that candidates would realise that the rate of facilitated diffusion would increase with the concentration of chloride ions, and that the graph would level off as the carrier proteins become saturated. Although the difficulty index indicates this was not a hard question it did not discriminate as well as expected with many of the stronger candidates opting for graph D.

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