CAIE A Level Biology 9700 · Cell membranes and transport
The cell surface membrane of a human intestinal epithelial cell contains both carrier proteins and channel proteins. For example, glucose is transported into the cell by facilitated diffusion via a carrier protein, while chloride ions move through a channel protein.
Outline the differences between carrier proteins and channel proteins in terms of their structure, mechanism of transport, and specificity.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Outline means: Give the main points briefly. Less detail than describe, but every key step has to be there. One short line per step, in order. The marks are for coverage, not depth.
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