Second messenger

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In biology, second messengers are low-weight diffusible molecules that are used in signal transduction to relay a signal within a cell. They are synthesized or released by specific enzymatic reactions, usually as a result of an external signal that was received by a transmembrane receptor and pre-processed by membrane-associated proteins. There are two basic types of second messenger molecules:

These intracellular messengers have some properties in common:

  • They can be synthesized/released and broken down again in specific reactions by enzymes.
  • Some (like Ca2+) can be stored in special organelles and quickly released when needed.
  • Their production/release and destruction can be localized, enabling the cell to limit space and time of signal activity.