LESSON 1 OF 3
What is a peptide?
By the end you can
- Explain what amino acids and peptides are
- Tell a peptide from a protein
- Name a few peptides the body makes on its own
Built from amino acids
Every peptide is made of amino acids, small molecules that work like building blocks. The body uses 20 standard amino acids. Each one has a name and a one-letter code, like G for glycine or K for lysine.
When amino acids link together in a row, the link between each pair is called a peptide bond. A short chain of amino acids joined this way is a peptide.
Peptide or protein?
The difference is mostly length. A chain of about 2 to 50 amino acids is usually called a peptide. Longer chains fold into complex 3D shapes and are called proteins.
Size matters because it changes how the molecule behaves. Peptides are small enough to make in a lab, one amino acid at a time. Large proteins usually have to be grown in living cells.
Your body already runs on peptides
Many of the body's messengers are peptides. Oxytocin is 9 amino acids long. GLP-1, released by the gut after a meal, is about 30. Insulin, at 51 amino acids, sits right on the line between peptide and protein.
Most research peptides are either copies of natural peptides, fragments of larger proteins, or lab-designed versions of either.
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Key terms
- Amino acid
- One of the 20 building blocks used to make peptides and proteins.
- Peptide bond
- The chemical link between two amino acids in a chain.
- Peptide
- A short chain of amino acids, usually 2 to 50 long.
- Protein
- A long amino acid chain, usually over 50, folded into a 3D shape.
- Sequence
- The exact order of amino acids in a chain, written with one-letter codes.
Remember
- Peptides are short chains of amino acids.
- Length is the main difference between a peptide and a protein.
- Many natural hormones and messengers are peptides.