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ACT Membranes study materials
ACT Membranes study resources

ACT Membranes: Membrane Dynamics and Trafficking

ACT Membranes · Work through your exam, one topic at a time.

All guide sections

Membrane Dynamics and Trafficking

Core concepts

Membranes are dynamic: they bud, fuse, and exchange material through vesicles. Know the secretory pathway (ER → Golgi → plasma membrane or lysosome) and endocytic pathways (phagocytosis, pinocytosis, receptor-mediated endocytosis). Vesicle formation uses coat proteins (COPI, COPII, clathrin); fusion requires SNARE proteins and Rab GTPases for targeting. The plasma membrane also renews through exocytosis and internalizes material through endocytosis.

Concepts to name

  • Exocytosis, endocytosis, vesicle budding and fusion
  • COPI (Golgi-to-ER retrograde), COPII (ER-to-Golgi), clathrin (endocytosis and some Golgi traffic)
  • SNAREs (v-SNARE and t-SNARE) and Rab GTPases
  • Receptor-mediated endocytosis, endosome, lysosome, phagosome
  • Membrane recycling and asymmetry maintenance

Traps

  1. Mixing up COPI and COPII directions - COPII is ER-to-Golgi (forward); COPI is Golgi-to-ER (retrograde).
  2. Forgetting that SNAREs mediate fusion while Rabs mediate targeting/docking.
  3. Assuming all endocytosis is receptor-mediated - pinocytosis and phagocytosis are distinct.
  4. Overlooking that membrane is conserved: exocytosis adds membrane, endocytosis removes it.

Worked example / rule of thumb

Rule: "COPII goes forward, COPI comes back." For fusion, remember SNAREs are the zipper that pulls membranes together, and Rabs are the address label that ensures the right destination. If a question asks how LDL enters a cell, answer receptor-mediated endocytosis via clathrin-coated pits.