Protein

A protein is a molecule made of one or more chains of amino acids. Its sequence and folded structure enable roles including catalysis, signaling, transport, and physical support.

Amino acid: An organic molecule containing amino and carboxyl groups; amino acids are the subunits of proteins. Proteins are assembled from amino acids joined in a specific sequence.
Protein folding: The process by which a protein chain adopts a three-dimensional structure. Folding creates the shapes that make many protein functions possible.
Hemoglobin: An oxygen-binding protein in red blood cells that transports oxygen through vertebrate blood. Its reversible oxygen binding is a clear example of protein-mediated transport.
Gene: A DNA sequence that contributes to a functional product, such as a protein or functional RNA. Genes encode many proteins, though gene expression includes several steps beyond translation.
Protein misfolding: The failure of a protein to adopt or maintain a functional three-dimensional structure. Misfolding can impair protein function or cause harmful aggregates.
Peptide bond: A covalent bond linking the carboxyl group of one amino acid to the amino group of another. These bonds connect amino acids into a protein’s backbone.
Enzyme: A biological catalyst that accelerates a chemical reaction without being consumed by it. Many enzymes are proteins whose active sites catalyze specific reactions.
Collagen: A fibrous structural protein that is a major component of connective tissues. Collagen’s tensile strength helps support skin, tendons, cartilage, and bone.
Messenger RNA: An RNA molecule that carries coding information used to synthesize a protein. Messenger RNA provides the sequence template read during protein synthesis.
Prion: An infectious protein form that propagates by inducing the misfolding of normally folded versions of the same protein. Prions demonstrate that a protein’s shape can transmit biological information.

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