Proteins and Enzymes

ID #2379

In chemistry, Hydrogen bonding is part of Covalent bonding. But in biology, it seems that covalent typically refers to the bonds between molecules such as glycosidic linkage, peptide bond or esther linkage, etc. Could you explain the terminology please?

A covalent bond is created by two atoms of similar electronegativities sharing a pair of electrons equally. The bond between N--C in a peptide bond is a good example of a covalent bond. I know chemistry breaks covalent bonds down further into subcategories, but we will not make those distinctions in this class. 
A hydrogen bond is a special bond that occurs between a hydrogen that is already partially charged due to its involvement in a bond with a highly electronegative atom (F, O, or N) and the partially charged highly electronegative atom of a second molecule near the hydrogen. It is because of these two partially charged atoms in two different molecules and the close proximity of the two molecules that a hydrogen bond develops. For example, two water molecules can hydrogen bond in O--H...O--H where the dots are the hydrogen bond. Since water plays such an important role in a cell and hydrogen bonding occurs frequently, we make it a separate category in this class. 

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