Protein
![A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. This protein was the first to have its structure solved by X-ray crystallography. Towards the right-center among the coils, a prosthetic group called a heme group (shown in gray) with a bound oxygen molecule (red).](/Images/godic/202502/03/Myoglobin3845.png")
![Chemical structure of the peptide bond (bottom) and the three-dimensional structure of a peptide bond between an alanine and an adjacent amino acid (top/inset)](/Images/godic/202502/03/Peptide-Figure-Revised3845.png")
![A ribosome produces a protein using mRNA as template](/Images/godic/202502/03/Ribosome_mRNA_translation_en.svg3845.png")
![The crystal structure of the chaperonin, a huge protein complex. A single protein subunit is highlighted. Chaperonins assist protein folding.](/Images/godic/202502/03/Chaperonin_1AON3845.png")
Proteins (/ˈproʊˌtiːnz/ or /ˈproʊti.ᵻnz/) are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within living organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.