Protein Structures

Today I had a quiz in Bio285, Cell and Molecular Biology I, a class I am in as a senior amongst many sophomores and juniors. The quiz was on basic protein structure and folding, but some of the questions were pretty tricky. The primary structure is the first level of proteins, and it is the sequence of amino acids in a polypeptide held together by peptide bonds. The second level is the secondary structure, which is the folding of the backbone. Secondary structure is held together by hydrogen bonds between amino and carboxyl groups of different amino acids. The third level is the tertiary structure, which is the interacting and folding of R groups. Tertiary structure can be influenced by many types of bonds, covalent and non-covalent, including disulfide, hydrogen, Van der Waal’s interactions, electrostatic interactions, and hydrophobic interactions. The type of bonds formed depends on the polarity and charge of the R groups. The fourth and final level of protein structure is the quaternary structure. This consists of multiple polypeptides interacting together, and they can be different polypeptides or multiple of the same. These are held together by all the bonds mentioned in tertiary structure bonding.