Endocytosis takes material into a biological cell by inward budding and separation of part of its cell membrane. At a chemical synapse, it helps recover membrane and proteins after synaptic vesicle exocytosis. This recovery is distinct from uptake of individual neurotransmitter molecules through membrane transport proteins.
synaptic vesicle recycling retrieves and reuses membrane and components after synaptic release. Uptake, uncoating, sorting and preparation for subsequent release are distinct measurable steps.
clathrin-mediated endocytosis internalizes selected surface material through assembly of adaptors and a clathrin coat, membrane deformation, scission and subsequent coat release. Counts of coated puncta alone do not distinguish initiation, successful internalization and stalled intermediates.
Phagocytosis encloses a large extracellular particle by extending and closing the cell membrane around it. It is one possible conceptual route for internalizing a symbiotic partner, but a modern phagocytic pathway should not be assumed to have existed before eukaryotic organization evolved.
