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

Exocytosis & endocytosis

• The processes of endocytosis and exocytosis move large substances or large amounts of substances into and out of cells

  • 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 materials are transported out of cells:

  1. The substance to be released is packaged into internal vesicles

  2. These vesicles then travel to the plasma 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 large molecules and particulate matter:

  1. The plasma membrane folds in on itself to form new vesicles

  2. Material from the external environment is engulfed by the vesicle

  3. The vesicle then carries the material 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