- enzymes
- toxins
- mucus
- extracellular matrix
- organic acids
- gases
- signaling compounds
Operational definition
Accounting output.
Compounds synthesized or processed by the organism and transported outside its cells or tissues while serving a biological, ecological, or metabolic function.
Examples include:
- extracellular enzymes;
- mucus;
- toxins;
- signaling compounds;
- extracellular matrix;
- organic acids;
- siderophores.
A secretion is not necessarily a waste product.