ABSTRACT

The electrons in the covalent bonds between oxygen and hydrogen are skewed toward the more electronegative oxygen, leaving the hydrogen proton somewhat exposed. There is an attraction between a lone pair of one water molecule and a hydrogen proton of another water molecule and that interaction is called a hydrogen bond. The energy needed to break an H bond is about that generated by the heat from an object at room temperature H bonds are therefore of marginal stability at room temperature. Water's high heat capacity has far-reaching biological consequences. The water in a lake changes its temperature slowly when the air temperature above it goes up or down, thus protecting temperature-sensitive aquatic organisms. Each residue can participate in two such H bonds, meaning that a typical polypeptide may have several hundred. There are enough H bonds in typical proteins to maintain the secondary and some of the tertiary structures of those complex compounds.