What Is A Hydrogen Bond?

Hydrogen bonds are some of the most important and ubiquitous forces responsible for the structure, shape and stability of biological systems. Hydrogen bonds are strong attractive forces between molecules created when a hydrogen atom is attracted to a small, electronegative atom like oxygen, nitrogen or fluorine. Hydrogen bonds make up a large portion of the intra- and intermolecular forces in living organisms.

The Nature of Hydrogen Bonds

A hydrogen bond is not a chemical bond in the same way other covalent and ionic bonds are. It is a weaker intermolecular force that occurs when a hydrogen atom, being slightly positively charged (due to its single valence electron which is easily attracted and repelled) is attracted to an electronegative atom like oxygen, nitrogen or fluorine. The hydrogen atom therefore donates its electron to the other atom, forming a transient bond between the two species.

The Strength and Role of Hydrogen Bonds

Hydrogen bonds are much weaker than covalent and ionic bonds, usually ranging from 0.3-3.0 kcal/mol in strength. Despite this, hydrogen bonds are vitally important in biology as they give proteins their structure, catalyse reactions, maintain DNA double helix structure, and are responsible for the secondary, tertiary and quaternary structure of proteins. Hydrogen bonds also mediate interactions between small molecules and proteins, giving them added stability and protection. In sum, without hydrogen bonds biology would not exist as we know it.