The cells of living organisms are made up of large molecules that are responsible for their overall structure and functioning. These large molecules are referred to as biological molecules or macromolecules, and each macromolecule is made up of its own monomers. These monomers are bound by different kinds of bonds, based on the location and function of the cell.
Covalent bonds, one of the strongest types of bonds, are the most common and the most compatible type of bonds found in biological molecules. Ionic bonds can harm a cell, hydrogen bonds are weak bonds, peptide bonds are only found in proteins. Therefore, most biological molecules are bound by covalent bonds.