What a peptide is

You may know insulin as the thing people with diabetes inject. When you eat, sugar from your food ends up in your blood. Your cells want to burn that sugar for energy, but can't on their own. Insulin is the key that unlocks your cells and lets the sugar in. If you have diabetes, your body stops making enough insulin, so the sugar stays locked out in your blood. Your cells go hungry surrounded by fuel they can't reach, and the sugar left sitting in your blood slowly does damage. Injecting insulin gives your cells the key they're missing.

Why are we talking about insulin? Well, insulin is a peptide. Peptides are just short chains of amino acids. They are small building blocks that link together like beads on a string. Your body makes thousands of different peptides this way, each a different order of beads doing a different job. Insulin's job is to unlock your cells so sugar can get in.

Those same building blocks also make proteins, which are just much longer chains, like the ones in your muscles. We get into the line between a peptide and a protein in the next lesson.

The peptides that people research and that you often hear about like retatrutide and GHK-Cu work the same way. They're short chains of amino acids that copy signals your body already makes. They can also be a slight tweak of an amino acid chain that is built to last longer than the ones you naturally produce. Don't think about it as putting something foreign into your body, but rather as adding more messages that your body already knows how to read.