What a peptide is.

A short chain of amino acids. That tells you what it's made of, not what it does or whether it works.

Chains of building blocks

Amino acids link into chains. The order of the links is the sequence. Change the order and you get a different molecule that behaves differently.

Peptides and proteins are built the same way. Peptides are usually the shorter ones, but where the line sits depends on who's drawing it. Length doesn't tell you what a molecule does.

Signals and receivers

Some peptides carry messages between cells. A receptor is the molecule that picks up the message and starts a response. Binding, switching on and the effect that follows are separate steps.

A lab-made peptide can look a lot like a natural one, and a small chemical change can still alter what it does. So a familiar name or a similar sequence doesn't make two products the same.

Many uses, one word

Peptides come up in metabolism, immunity, skin and nerve research, and more. Some are in prescription drugs. Others have only been tested in cells or animals. "Peptide" tells you the kind of molecule. It says nothing about the evidence.

Words you'll see

Sequence. The order of amino acids in a chain.
Analogue. A molecule designed to be similar to another one.
Receptor. The molecule that picks up a signal.
Mechanism. An explanation of how an effect might happen.
Formulation. How an ingredient is made into a product.