Hint: Proteins are defined as the biological polymers. They are polymers of amino acids that are formed by joining together by amino acids. You must be well known that amino acids are the building blocks of proteins. It means that proteins possess chain-like structure, where amino acids are the primary ingredient.
The amino acids get linked together with peptide bonds to form proteins. When such a few bonds get connected together, it becomes a polypeptide chain. When one or more of these polypeptide chains gets twisted and it leads to formation of a protein. On the basis of this the protein acquire different structure:
Secondary Protein Structure
This secondary protein structure provides a unique shape to the protein. It occurs at the place where the peptide backbone of a protein structure gets folded onto itself. The folding of the polypeptide chains takes place because of the interaction between the carboxyl group and amine groups of the peptide chains.
Secondary protein structure provides two types of shapes; they are a-helix and B-pleated sheets.
a-helix - The backbone of protein possesses a helical structure. In between different layers of the helix, the hydrogen makes bonds with oxygen, rendering helical structure.
B-pleated sheet - In this shape, polypeptide chains get close next to each other. The external hydrogen molecules of these chains make intramolecular bonds
Tertiary Protein Structure
Tertiary structure leads to formation of 3-D shape of the protein. As amino acids make bonds at the time of secondary structure, they give out shapes such as helices and sheets. The structure can coil or fold randomly, and that's what is termed as tertiary structure of proteins.
Quaternary Protein Structure
The spatial arrangement of two or more peptide chains leads to development of quaternary protein structure.
Note: You should be always confirmed that proteins don't necessarily need to have a quaternary structure. Also note that primary, secondary, and tertiary structures of proteins are present in all-natural proteins.