Describe five important features of the fluid mosaic model of membrane structure proposed by S.L Singer and G.L Nicholson.

The fluid mosaic model is used to represent the structure
of the cell membrane.  The cell membrane is flexible and can move and shift sideways,
much like a liquid shifts from side to side in a container when the container is
disturbed.  It is because of the cell membrane's ability to shift that it is considered
to be "fluid". 

A mosaic is a substance that is made up of
a bunch of different parts (imagine a mosaic picture).  The cell membrane is also made
up of  different parts that are integrated together, and this is where the mosaic part
comes in.  The cell membrane is made up of lipids, proteins, and cholesterol.  The
proteins and cholesterol molecules are imbedded in the phospholipid bilayer.  The
proteins are important because they act like doors that allow certain molecules to enter
into or leave the cell. 

The cell membrane is a bilayer. 
This means that there are two layers sandwiched together.  Each layer consists of a
phospholipid that has a hydrophillic head and a hydrophobic tail.  The tails of each
layer point towards the center of the membrane and the heads of the layers are on the
outside.  Imagine a peanut butter sandwich.  You have two pieces of bread, each with one
side with peanut butter.  The peanut butter is on the inside on both pieces and the
outside is dry on both pieces and points to the environment.  Hydrophobic means water
fearing and hydrophillic means water loving.  This arrangement of the phospholipids
regulate which molecules can go in or out of the
cell. 

Summary

1.  fluid (can
move)

2.  mosaic (made up of a lot of differnt parts
integrated together)

3.  bilayer (helps regulate what goes
in and out)

4.  proteins (serve as markers on the surface
for identification purposes and to allow certain molecules in and
out)

5.  transport (passive and active, allows molecules
across membrane)