Some amino acids do double duty: they build proteins, but certain ones also work as neurotransmitters in your brain. These are called biogenic amines, and they're amino acids that signal between neurons.
Amino acids are used for many, many things in the body, but mostly for structural proteins in your body. So we make our own proteins. Next most common thing would be like enzymes. They're the skeleton of enzymes a lot of the time. And then they're used for other things. Well, there's a group of amino acids that are also called biogenic amines. And biogenic amines are simply amino acids that are also used in the neurological system, in the nervous system.
