The vast majority of biological processes rely on proteins and they are often referred to as the building block of life. Proteins are macromolecules, formed from the 20 amino amino acids used for life. In this essay I will be explaining the forces involved in maintaining protein structure, by explaining them at each level. .
Primary Structure and Peptide Bonding.
Protein structure is divided into four main levels; primary, secondary, tertiary and quaternary, according to the increasing complexity of the proteins conformation. Primary structure is at the most basic level, with amino acids linked in a linear polypeptide chain, by peptide bonding, which is a type of covalent bond. Covalent bonds are formed by atoms with similar electronegativity, which each donate a valence electron to form a shared electron-pair bond. A polypeptide chain is composed of adjacent amino acids, where the α-carboxyl group of an amino acid is linked to the α-amino group of the adjacent amino acid. This chain acts as a rigid backbone, as the peptide bonds are planar, although side-chains can move more freely. As a peptide bond forms, water is released, making it a condensation reaction. The bond formed has double-bond character due to a resonance structure formed by the nitrogen atoms long pair of electrons. This is what makes peptide bonds planar, as atoms cannot rotate around this rigid bond. Although the peptide bond is planar, rotation can still occur at the alpha carbon, so that polypeptide chains are flexible.
Secondary Structure and Hydrogen Bonding.
Secondary structure is where we find the first inner structures of the protein forming. The structures formed are dependent on the amino acid sequence present in the primary structure. The two most common secondary structures are the α-helix and β-pleated sheet. The key intramolecular force of proteins is hydrogen bonding as it is responsible for the formation of the inner structures.