20. This process is known as exocytosis.
A vacuole approaches the inside of the lipid bilayer making
up the plasma membrane. It then contacts this membrane, and according to the
fluid mosaic model of plasma membranes, the lipids in the vacuole flow into
the plasma membrane. As the two sets of membrane lipids join, an opening to
the outside is made and the contents of the vacuole are squeezed out.
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Slichter