Protein
A protein is a large biomolecule composed of 50 or more amino acids folded into a specific three-dimensional structure. Proteins serve structural, enzymatic, and signaling roles throughout the body.
Overview
Proteins are the workhorse molecules of biology, performing functions ranging from catalyzing chemical reactions (enzymes) to providing structural support (collagen) and transporting molecules (hemoglobin). The boundary between peptides and proteins is generally placed at 50 amino acid residues, though this cutoff is a convention rather than a hard rule. Unlike most research peptides, proteins are too large to be absorbed intact through the gut and cannot typically be administered subcutaneously without loss of activity — HGH, for example, must be injected. Proteins are also more prone to denaturation (loss of structure) from heat, pH changes, or mechanical agitation than smaller peptides.
Related Terms
Frequently asked questions
Is HGH a peptide or a protein?+
HGH (human growth hormone) is a 191-amino-acid protein, making it technically a protein by size. However, it is often discussed alongside research peptides because GHRH and GHRP peptides are used to stimulate its endogenous release.
Can proteins be used as research compounds like peptides?+
Some proteins are used in research and medicine (e.g., insulin, HGH), but their larger size makes formulation and administration more complex than most small peptides.
What holds a protein's 3D structure together?+
Disulfide bonds, hydrogen bonds, ionic interactions, and hydrophobic forces all contribute to maintaining a protein's folded structure. Loss of this structure (denaturation) inactivates the protein.