Large molecule or , consisting of amino acids, polypeptides, and other substances, that serves as the key component that implements the functions encoded by hereditary material.
Proteins consist of polymers of amino acids (polypeptides) along with other, non-amino acid substances, such as the found in the proteins and . Proteins are the primary facilitators of phenotype, as viewed both at cellular and organismal levels.
The following video is a nice introduction to different types and representations of protein structure, shown both in static and dynamic forms:
It is important to not confuse the concept of protein with that of polypeptides since the two terms, though related, are not identical. Indeed, much discussion of proteins, such as the many details of (particularly, the process of translation) are actually more correctly viewed as discussions of the synthesis of polypeptides rather than, strictly, of proteins.
Proteins can be differentiated into a number of components including polypeptide (or polypeptides) along with cofactors (and coenzymes). For the subset of proteins known as enzymes, the polypeptide portion alone is called an apoenzyme whereas the combination of polypeptide(s) and cofactor(s), forming an active enzyme, is known as the holoenzyme. Polypeptides often are functional within proteins in combination with other polypeptides, forming , , etc.
Many and in our serve as cofactors or coenzymes. Proteins requiring these substances are unable to function without them. You can think of these other substances as supplying more chemical properties, that is, chemistry to proteins that is other than what individual amino acids can provide. In proteins that employ these other substances there will be amino acids that together form structures which hold on to them, and typically these cofactors and coenzymes will be held at what is known as an enzyme's or protein's active site.
The following is a list of terms associated with proteins generally (but not necessarily with enzymes also):
Alpha helix, Amino acid, Apoenzyme, Beta pleated sheet, Colloid, Deamination, Denaturation, Disulfide bridge, Enzyme, Globular protein, Glycine, Glycoprotein, Holoenzyme, Integral membrane protein, Ion channel receptor, Membrane protein, Methionine, Peptide bond, Peripheral membrane protein, Polypeptide, Polypeptide backbone, Post-translational modification, Protein, Protein activation, Protein folding, Protein primary structure, Protein secondary structure, Protein tertiary structure, Protein quaternary structure, Proteoglycan, Receptor protein, R group, Salt Bridge, Secreted protein, Signal sequence, Sodium-potassium pump, Transmembrane protein, Transport protein
The following are examples of different types of proteins (see also enzymes):
Actin, cAMP receptor protein, Catabolite gene activator protein, Collagen, G protein-linked receptor, Histones, Insulin, Perforin, Tubulin, Tyrosine kinase receptor