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B1.1.12—Phospholipid bilayers

Phospholipids are amphipathic molecules whose hydrophilic phosphate heads and hydrophobic fatty-acid tails self-arrange into stable membrane bilayers in water-rich environments.

Syllabus
First assessment 2025
Objective
B1.1.12
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2021
Most common paperPaper1
Typical marks1

Common command terms

  • Outline
  • Annotate

Scoring notes

Common mistake
Reversing the hydrophilic phosphate head and hydrophobic fatty-acid tails.

Recent exam appearances

November 2021Paper1 ["HL"] · TZ04[ 1 ]B1.1.12—Phospholipid bilayers
Practice this objective

Coverage 2021–2021 · Updated 15 Jul 2026

Concept essentials

  • Phospholipid heads are hydrophilic and phosphate-containing.
  • Fatty-acid tails are hydrophobic and avoid water.
  • In water, phospholipids self-arrange so tails are shielded from water.
  • Phospholipid bilayers form the basic barrier structure of cell membranes.
ConceptIB Biology HL