Did you notice that the molecules shown above have a particular shape to
them?
Molecules will form into shapes such that regions of high electron density
(where electrons are being shared between atoms and where there are unshared
pairs of valence electrons on the surface).
Because all of these regions are negatively charged, they repel each other
and try to move as far away as possible from each other.
Depending on how many atoms are bonded and if there are unshared pairs of
electrons around, you will see the following common shapes:
Tetrahedral
Trigonal Pyramidal
Trigonal Planar
Bent
Linear
Check out the images of molecules below and see where
you can find these shapes within them. The images are being displayed by the
Chime plug-in which allows you to manipulate and take measurements on the
displayed molecules. See the Using
the Chime Plug-in sheet for instructions.
The shape of molecules is extremely important, especially for larger more
complex molecules. Below are several examples showing how shape is the key
factor in a molecules biological function.
Immune function: Our immune system has the capability to recognize
foreign material that enters our body. It does this not by "thinking"
about it. After the first time our immune system encounters a pathogen,
it makes antibodies that are just the right shape to bond with
the foreign antigen. Below is an example showing the antibody molecule
in green and the antigen in red:
Hide/Show the antigen.
The synthesis of ATP (the primary energy storing molecule
in our body) happens in a series of steps using ATP synthase.
