title: The
Phospholipid molecule
Draw and label this:
Hydrophilic –
“water loving”
Hydrophobic –
“water fearing”
The cell membrane is a phospholipid bilayer - this means that
there are two rows of phospholipid molecules with the fatty acid
tails in the middle making it nonpolar. The phosphate based
heads are on the inner and outer sides of the membrane where
polar water molecules can interact with the cell membrane.
Membranes are vital because they separate the cell from the outside world.
They also separate compartments inside the Plasma Membrane
nonpolar
Extracellular fluid
Cytosol – just the
fluid in the cell
Cytoplasm – the fluid and
organelles inside the cell
The plasma membrane serves as the interface between
the machinery in the interior of the cell and the
extracellular fluid (ECF) that bathes all cells.
The lipids in the plasma membrane are chiefly
phospholipids like phosphatidyl ehtanolamine and
cholesterol. Phospholipids are have a non-polar
hydrocarbon tail of the molecule that is hydrophobic
There is a polar head that is hydrophilic. As the plasma
membrane faces watery solutions on both sides, its
phospholipids accommodate this by forming a
phospholipid bilayer with the hydrophobic tails facing
each other.
Phospholipid bilayer: