Both are chains of amino acids, but they differ fundamentally in size, complexity, and function.
Size
2–50 amino acids
50+ amino acids (often hundreds or thousands)
Structure
Usually linear or simple folds
Complex 3D folding (tertiary/quaternary structure)
Function
Often act as signals, hormones, or modulators
Structural components, enzymes, antibodies
Stability
Generally less stable, shorter half-life
More stable due to complex folding
Synthesis
Often made by chemical synthesis
Usually made by ribosomes in cells
Examples
Oxytocin, BPC-157, DSIP, GHK-Cu
Insulin, collagen, hemoglobin, antibodies