substrate

In chemistry, the term substrate is highly context-dependent. Broadly speaking, it can refer either to a chemical species being observed in a chemical reaction, or to a surface on which other chemical reactions or microscopy are performed. In biochemistry, an enzyme substrate is the molecule upon which an enzyme acts. In synthetic and organic chemistry a substrate is the chemical of interest that is being modified. A reactant is added to the substrate to generate a product through a chemical reaction. Otherwise, substrate may refer to a surface on which other chemical reactions are performed or a surface that plays a supporting role in various spectroscopic and microscopic techniques.

Microscopy