Protein structure and synthesis
Protein synthesis occurs in cells through a process called translation. The genetic code for a protein, in the form of messenger RNA (mRNA), is read by a ribosome, which then assembles the appropriate sequence of amino acids according to the code. The process of translation requires the help of transfer RNA (tRNA) molecules, which deliver the correct amino acid to the ribosome. Once proteins are synthesized, they are further folded into their unique 3D structure.
There are hierarchical degrees of complexity in the formation of a mature, fully-folded protein. Primary structure describes a linear chain of amino acids formed by sequential peptide bonds. The secondary structure consists of backbone interactions in the polypeptide chain that are stabilized by hydrogen bonds between amino acids, forming α-helices and β-pleated sheets. In tertiary structure, secondary structures come together and further orient themselves depending on hydrophobic interactions, ionic interactions, and disulfide bridges. Finally, the quaternary structure consists of multiple tertiary structures coming together to form subunits of a larger protein.