Paper 2 · cell membranes
Fig 1.1 shows a diagrammatic model of a cell surface membrane. Name the structure labelled P.
Model answer
cholesterol
Explanation: P is a small lipid molecule embedded among the phospholipid tails of the bilayer. It regulates membrane fluidity, making the membrane less fluid at high temperatures and less rigid at low temperatures, which is the role of cholesterol in the cell surface membrane.
Derived from ZIMSEC Biology Paper 2, November 2008, Q16
