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B2.1.13 (HL)—Membrane fluidity and vesicles

Membrane fluidity lets vesicles bud, move, and fuse during endocytosis, exocytosis, and intracellular transport of materials; These events connect membrane structure to uptake, secretion, and intracellular movement.

Syllabus
First assessment 2025
Objective
B2.1.13
Level
HL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper2
Typical marks1–5

Common command terms

  • Describe
  • Identify
  • State
  • Explain

Scoring notes

Common mistake
Naming endocytosis without describing membrane invagination and vesicle formation.

Recent exam appearances

May 2023Paper2 ["HL"] · TZ18(a)[ 5 ]B2.1.13 (HL)—Membrane fluidity and vesicles
May 2021Paper2 ["HL"] · TZ22(a)(ii)[ 1 ]B2.1.13 (HL)—Membrane fluidity and vesicles
November 2015Paper2 ["HL"] · TZ06(c)[ 5 ]B2.1.13 (HL)—Membrane fluidity and vesicles
May 2013Paper2 ["HL"] · TZ12(b)[ 2 ]B2.1.13 (HL)—Membrane fluidity and vesicles
Practice this objective

Coverage 2013–2023 · Updated 15 Jul 2026

Concept essentials

  • Fluid membranes can change shape to form vesicles.
  • Endocytosis takes material into cells by enclosing it in a vesicle.
  • Exocytosis releases material when vesicles fuse with the plasma membrane.
  • Vesicles also transport materials between organelles inside cells.
ConceptIB Biology HL