Question

Biochemistry question:

Describe the four levels of proteins structure (primary, secondary, tertiary and quaternary). Make sure to describe the role of non-covalent interactions involving the main chain or side chains of the amino acids that form to stabilize the structure.

Answer 1

The four levels of protein strucure are :

1. Primary structure:It is the first level of protein structure in which aminoacids are joined by peptide bonds in a specific linear sequence to form a polypeptide.
2. Secondary structure:This is the second level of protein structure that includes coils and folds that take place along the peptide backbone,This includes formation of alpha helix via hydrogen bonding between atoms i.e between carbonyl oxygen and amino hydrogen atoms of the peptide back bone and formation of beta-pleated sheets that are formed by one or more strands of a polypeptide that align parallel to one another and form hydrogen bonds between carbonyl oxygen and amino hydrogen atoms in the peptide backbone.
3. Tertiary structure:This represents the third level of protein structure in which interactions occurs either between the R groups or between R groups and the peptide backbone so that a unique three-dimensional shape of a polypeptide is formed. Salt bridges, hydrogen bonds,disulfide bonds,non specific hydrophobic interactions are involved.
4. Quatenary structure:This represents the fourth level of protein structure in which two or more identical or non identical polypeptide that have already folded into the tertiary structures interact further to form a single active protein unit.Hydrophobic interactions in which nonpolar side chains of a polypeptide are  clustered and grouped to minimize contact with water molecules;and disulfide bridges between cysteine residues are involved.