The big idea: Vesicles are small membrane sacs that carry materials between compartments and to the plasma membrane; the protein clathrin helps them form.
The points to remember
- A vesicle is a small sac of membrane with cargo inside.
- Vesicles carry proteins from the rough ER to the Golgi apparatus, and from the Golgi to the plasma membrane (secretion) or to lysosomes.
- Clathrin proteins bind to the inner face of a membrane and to each other, forming a coat that pulls the membrane into a bud.
- The coated vesicle detaches; the clathrin coat then falls away so the vesicle can fuse with its target.
- Because membranes are fluid, vesicles can bud off one membrane and fuse with another.
Remember it as: Clathrin pulls it in and pinches it off; the vesicle carries it on.
Real example: nerve endings: After a nerve ending releases neurotransmitter by exocytosis, clathrin-coated vesicles take membrane back in within seconds, so the ending can be refilled and fire again.
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How it is asked: Expect a Paper 1A item on the role of clathrin, or a short Outline of how vesicles form or what they carry.
IB-style questionOutline[2 marks]
Outline the role of clathrin in the formation of vesicles.
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See the answer broken into clear points, with guidance on how each point earns marks.