Peptides have two origins. Some the body makes itself; others are made in a laboratory. For someone just starting out, that raises a question: is a lab-made peptide something different from a body's own peptide? The short answer is no: it is the same type of molecule, arrived at by a different route. Both routes follow below, up to the point where they meet.
Made by the body
Some peptides come from the body itself. The body produces them from its own building instructions and places the amino acids in the right order.
A well-known example is insulin. Insulin consists of fifty-one amino acids, divided over two linked chains, and is a body's own peptide.
The order of those amino acids, the sequence, is what gives the molecule its identity. That principle from the first crash course holds regardless of origin.
In short. The body makes peptides itself, following its own building instructions. The sequence is what gives the molecule its identity.
Made in the lab
Peptides can also be made in a laboratory. That process is called synthesis: the chain is built up step by step, one amino acid at a time, in a predetermined sequence.
A synthesised peptide can be a copy of a body's own peptide, or a new variant that does not occur in nature. Researchers use that possibility to study what a particular sequence does.
Because the sequence is set in advance, the result is a defined substance: known in composition, and therefore usable in research where precision matters.
In short. In synthesis the chain is built up step by step in a predetermined sequence. The result is a defined substance, known in composition.
The same molecule, one framework
Here the routes meet. A lab-made copy of a body's own peptide is the same type of molecule as the original: the same chain, the same sequence.
The difference lies not in what it is, but in where it comes from and how certain the composition is known. How a synthesised peptide is both made and checked is a story of its own; that is the subject of the deep dive Research-grade in Practice.
What is used in a research context falls under a clear framework: research use only, meaning strictly for laboratory research, not for use in humans or animals.
In short. A peptide can be the body's own or synthesised in the lab. The origin differs; the type of molecule is the same, and the sequence remains the identity.
Read further
The deep dive Research-grade in practice shows how a synthesised peptide is made and checked step by step. The first crash course lays the basis under the terms sequence and synthesis.
Research-grade in practice →Peptides Crash Course →This article explains origin and makes no statements about effects in humans or animals.