CAIE A Level Biology 9700 · Cell membranes and transport
A scientist uses freeze-fracture electron microscopy to study the structure of a cell surface membrane. The image reveals a bilayer with embedded proteins, some spanning the membrane and others on the surface.
Outline the fluid mosaic model of membrane structure, describing the arrangement of phospholipids and proteins. In your answer, explain the difference between carrier proteins and channel proteins in terms of their roles in transport across the membrane.
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.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.