What Are Peptides? A Plain-English Guide to How They Work

The word peptide gets used a lot in health and research circles without much explanation. If you are new to this area, here is a plain-English account of what peptides are, how they work, and why they are the subject of so much research.

The Basic Definition

A peptide is a short chain of amino acids. Amino acids are the building blocks of protein — your body uses 20 of them to build everything from muscle fibres to enzymes to hormones. When amino acids link together in a chain, that chain is called a peptide. Short chains (typically under 50 amino acids) are peptides. Longer chains are proteins.

So a peptide is essentially a short protein. The distinction matters biologically because size affects how a molecule behaves in the body — how it is absorbed, how it crosses cell membranes, how quickly it breaks down, and which receptors it can interact with.

Natural Peptides in the Body

Your body produces hundreds of peptides naturally. Insulin is a peptide. Growth hormone is a peptide. Many hormones and signalling molecules are peptides. They act as messengers, telling cells and tissues to do specific things — produce collagen, release energy, suppress appetite, trigger repair processes.

The peptides in G&D Pharma's library are either identical to naturally occurring peptides, derived from naturally occurring peptides, or synthetic analogs designed to mimic or extend the effects of natural peptides.

How Research Peptides Work

Research peptides work by binding to specific receptors on cell surfaces and triggering biological responses. A peptide is like a key and a receptor is like a lock — the right peptide fits the right receptor and triggers a specific downstream process.

GDmounjaro binds to GLP-1 and GIP receptors and triggers the appetite suppression and metabolic effects associated with those pathways. GHK-Cu binds to receptors in skin fibroblasts and triggers collagen production. BPC-157 activates growth hormone receptors in tendon tissue and triggers repair processes.

Why Are They Administered by Injection?

Most research peptides are administered by injection because the digestive system breaks them down before they can reach the bloodstream in intact form. Stomach acid and digestive enzymes degrade peptide bonds efficiently — which is exactly what they are designed to do with dietary protein. Injection bypasses this degradation and allows the intact peptide to reach its target receptors.

Some peptides can be delivered nasally (Semax is an example in the G&D Pharma library) because the nasal mucosa offers a more direct route to the bloodstream and, for neuro-targeted peptides, to the brain via the olfactory pathway.

Research vs Approved Medicines

Some peptides in the G&D Pharma library are approved medicines (GDmounjaro and Tesamorelin). Most are research chemicals — compounds with promising evidence bases that have not completed the full regulatory approval process. Research chemicals are supplied for in-vitro and laboratory research use only. They are not medicines and are not supplied as treatments for any condition.