Ionic Bonds

What are ionic bonds ?

ionic bonds are forces of attraction between ions of opposite charge (+and -)

What kinds of biological molecules form ionic bonds?

any kind of biological molecule that can form ions

An example of a functional group that can enter into ionic bonds is shown below. The carboxyl group is shown.

Under the right conditions of pH the carboxyl group will ionize and form the negatively charged COO ion and a positively charged H ion (or proton)

Here is another representation of the carboxyl group. In this case the covalent bonds are shown by the lines and the shared electrons are shown by the black dots.

When ionization of the carboxyl group occurs a proton dissociates from the OH group, leaving the shared electrons behind with the oxygen. Thus the COO ion has an excess of electrons over protons and is an anion. The proton that is released has no associated electron and is therefore a cation.

What function do ionic bonds have in biology?

They are important in all biological processes. A few examples are:

They play an important role in determining the shapes (tertiary and quartenary structures) of proteins
They are involved in the process of enzymic catalysis
they are important in determining the shapes of chromosomes.
They play a role in muscle contraction and cell shape
They are important in establishing polarized membranes for neuron function and muscle contraction