Covalent bonds are forces that hold atoms
together. The forces are formed when the atoms of a
molecule share electrons. You will learn more about the chemistry of covalent
bond formation when you take Chemistry 1. For biological purposes there
are several things to remember about covalent bonds
- Covalent bonds represent chemical potential energy that can be used
in biological reactions. An example of this are the phosphoanhyride
bonds of ATP.
- The angles formed between covalently bonded atoms
are specific and defined. This means that biological molecules formed
with covalent bonds have definite and predicable shapes.
- In biological systems, covalent bonds are called strong
bonds. This means that they are not normally broken under biological
conditions unless by enzymic catalysis. This is in opposition to weak bonds like hydrogen and ionic bonds which are easily
broken under normal biological conditions of temperature and pressure.
- There is a type of covalent bond called a polar
covalent bond. In Biological systems, polar covalent bonds are important
because these kinds of bonds allow the formation of another kind of weak
bond called a hydrogen bond. Water is an example
of a molecule that has polar covalent bonds and engages in hydrogen bonding.
- In addition to polar covalent bonds, there are nonpolar
covalent bonds. In biological systems, if a molecules has a predominance
of nonpolar covalent bonds, that substance is hydrophobic.