Summary
Vesicles fuse with the plasma membrane to release their contents outside the cell.
In depth
Vesicles from the Golgi travel along cytoskeletal tracks and fuse with the plasma membrane, releasing contents and adding membrane. It can be constitutive (continuous) or regulated, such as calcium-triggered release of neurotransmitters.
Exocytosis balances endocytosis so the cell surface area stays constant.
Fusion is driven by SNARE proteins and triggered by calcium sensors such as synaptotagmin, which makes neurotransmitter release take under a millisecond. Botulinum and tetanus toxins cleave SNAREs and so block release, causing paralysis; the same effect is used for medical Botox.
In plants, exocytosis delivers wall components and enzymes to the cell surface, and in some cells it expels waste. Insulin granules in beta cells are released this way when glucose rises.
Remember: the vesicle membrane is added to the plasma membrane, so the lipid bilayer and the proteins inside the vesicle become part of the cell surface, with the vesicle interior now facing outward.
Frequently asked questions
What is Exocytosis?
Vesicles fuse with the plasma membrane to release their contents outside the cell.
Which area of biology covers Exocytosis, and how advanced is it?
Exocytosis is one of the 52 topics in Cell Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Vesicle Trafficking, Cytoplasm, Endocytosis.
Can you give an example of Exocytosis?
Pancreatic beta cells release insulin by exocytosis when blood glucose rises.
What should I learn before Exocytosis?
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Exocytosis. Intermediate topics assume the Beginner vocabulary.
What topics are related to Exocytosis?
The closest topics to Exocytosis are Vesicle Trafficking, Cytoplasm, Endocytosis, Facilitated Diffusion. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Exocytosis?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Exocytosis. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Exocytosis different from Vesicle Trafficking?
Exocytosis: Vesicles fuse with the plasma membrane to release their contents outside the cell. Vesicle Trafficking: Coat proteins and SNARE complexes sort, bud and fuse vesicles to move cargo between membrane compartments. Read both side by side and note what each one explains.
How should I study Exocytosis step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Vesicle Trafficking and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.