Proteins have a variety of functions within a living cell. Describe at least three of the possible functions of proteins, and explain how proteins can be so diverse when there are only a limited number of different amino acids.

anonymous 3 years ago Proteins are involved in almost all of the cell's functions. They can act as: Transportation: they can transport hydrophobic molecules in blood for example Regulation: protein hormones and enzymes Receptor: can act as receptors on cell surface and in the subsequent signal transduction (G-protein for instance) It is true that all proteins are made up of up to 20 amino acids, but there are several reasons for their diverse actions: - One reason is the possible sequence and number of amino acids: Met-Ser-His is different from Met-His-Ser for example. Besides, you have different chain length, for a protein is made up of long chain of polypeptide (longer than 50-70 amino acids) and can have any of the 20 amino acids with repetition, so using simple probability, this can provide up to practically unlimited combination with proteins that have chains of thousands of amino acids. - Another very crucial reason for the diversity of protein action is the conformation. A protein passes by at least 3 conformational stages before becoming mature. The straight amino acid chain is the primary structure of the protein that can never be active. Spatial modification of this primary structure results in a secondary structure, Helix or Beta-pleated sheets (or other coiling structure), that is also inactive. Further coiling and bending of the secondary structure produce a 3-dimentional conformation that is the active form of the protein. Moreover, many proteins can undergo further conformational rearrangement and combination with other protein sub-units producing a quaternary structure.