Paper 2 · Cell Structure and Membranes
The cell surface membrane is described as a 'fluid mosaic' model. Which of the following correctly explains why this description is used?
AThe membrane is completely rigid and fixed in overall shape, while only the carbohydrate chains on its outer surface form a repeating, tile-like mosaic pattern.
BThe phospholipids are arranged in a single, fixed layer that mimics the pattern of a mosaic tile.
CThe phospholipid molecules are free to move within the bilayer, and the protein molecules are scattered throughout it like tiles in a mosaic.
DThe protein molecules form a continuous, immobile mosaic layer that anchors the phospholipids in place.
Explanation: 'Fluid' refers to the phospholipid bilayer, whose molecules are free to move sideways within their layer, giving the membrane flexibility. 'Mosaic' refers to the protein molecules, which float about within or on the bilayer and are scattered through it, resembling the irregular scattered pieces of a mosaic, rather than forming a fixed, continuous, or single-layer structure.
Derived from ZIMSEC Biology Paper 2, November 2008, Q16
