Exocytosis & Endocytosis (College Board AP® Biology): Study Guide

Exocytosis & endocytosis

• The processes of exocytosis and endocytosis allow the transport of large molecules across the plasma membrane

  • They can also allow for the transport of whole cells, or parts of cells

• Exocytosis and endocytosis require energy, so they are forms of active transport

Exocytosis

• Exocytosis is the process by which large macromolecules are transported out of cells:

  • The substance to be released is packaged into internal vesicles

  • These vesicles then travel to the cell surface membrane where they fuse with the membrane and secrete their contents outside the cell

• Examples of exocytosis include:

  • the release of neurotransmitters during nerve impulse transmission

  • the secretion of insulin during blood glucose regulation

  • enzyme secretion in the digestive system

Endocytosis

• Endocytosis is the process by which cells take in macromolecules and particulate matter:

  • During endocytosis the plasma membrane engulfs material, forming a new vesicle from the membrane

  • The vesicle then carries the imported substance into the cell

• Examples of endocytosis include:

  • phagocytosis, during which cells of the immune system engulf and destroy pathogens

  • the ingestion of cholesterol in order to build new membranes

  • taking in water