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B2.1.2—Bilayers as barriers

The hydrophobic core of a lipid bilayer limits passage of polar, charged, or large substances while separating aqueous compartments; This barrier property explains why controlled transport proteins are necessary for many solutes.

Syllabus
First assessment 2025
Objective
B2.1.2
Level
SL

Concept essentials

  • The bilayer core is hydrophobic because fatty acid tails point inward.
  • Polar or charged substances usually need membrane proteins to cross efficiently.
  • Membranes separate aqueous spaces while controlling exchange between them.
ConceptIB Biology SL