Second messenger
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 other
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.