Here's a breakdown:

* Intracellular protein-containing vesicle: A small, membrane-bound sac within the cell that carries proteins destined for release outside the cell.

* Fusion with cell membrane: The vesicle's membrane merges with the cell's outer membrane.

* Expelling protein to outside cell: The protein contents of the vesicle are released into the extracellular space.

Exocytosis is a crucial process for many cellular functions, including:

* Hormone secretion: Cells release hormones like insulin and growth hormone through exocytosis.

* Neurotransmitter release: Nerve cells release neurotransmitters at synapses through exocytosis.

* Waste removal: Cells can expel waste products through exocytosis.

* Cell signaling: Cells use exocytosis to release signaling molecules that can interact with other cells.