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B2.1.4—Integral and peripheral proteins

Membrane proteins include embedded and surface-associated proteins that transport substances, receive signals, catalyse reactions, and support adhesion; Their positions explain how one membrane can perform many different cellular functions.

Syllabus
First assessment 2025
Objective
B2.1.4
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceMay 2023
Most common paperPaper2
Typical marks4–5

Common command terms

  • State
  • Identify
  • Outline
  • Describe
  • Explain
  • Label

Scoring notes

Common mistake
Listing non-membrane processes such as DNA replication or glycolysis as membrane protein functions.

Recent exam appearances

May 2023Paper2 ["HL"] · TZ27(b)[ 5 ]B2.1.4—Integral and peripheral proteins
May 2017Paper2 ["HL"] · TZ15(b)[ 4 ]B2.1.4—Integral and peripheral proteins
Practice this objective

Coverage 2017–2023 · Updated 15 Jul 2026

Concept essentials

  • Integral proteins are embedded in the bilayer and may span it completely.
  • Peripheral proteins are associated with membrane surfaces rather than crossing the hydrophobic core.
  • Membrane proteins can act as channels, pumps, receptors, enzymes, adhesion molecules, and communication sites.
  • Transport proteins are essential for moving many polar or charged substances across membranes.
ConceptIB Biology HL