Enzymes also can take two separate substrates and make them into one product (exact opposite of the above picture).
They are very specific to their substrates.

Vast majority of enzymes are proteins
Commonly end in -ase
If named well they often tell you what substrate they work on (for example, amylase digests amylose and amylopectin, which are its substrates)

Role of enzymes: -catalyze reactions in the body
-break down food into smaller molecules that cells can absorb.