the membrane. This pressure is defined as the osmotic pressure (Π) of the solution, and is given by
the formula:
Π = MRT
where M is the molarity of the solution, R is the ideal gas constant, and T is the temperature on the
Kelvin scale. This equation clearly shows that molarity and osmotic pressure are directly
proportional; that is, as the concentration of the solution increases, the osmotic pressure also
increases.
A CLOSER LOOK
The solute concentration in the cytoplasm of a cell relative to that of its environment
determines the net direction of the flow of water, and may lead to either shrinking or
swelling (maybe even bursting, or lysing) of the cell.The setup behind the concept of osmotic pressure, as described above, may seem at first glance
artificial and contrived, but actually is very important in cellular biology, because the cell membrane
is a semipermeable membrane that allows only certain types of molecules to diffuse through. The
solute concentration in the cytoplasm of a cell relative to that of its environment determines the net
direction of the flow of water, and may lead to either shrinking or swelling (maybe even bursting, or
lysing) of the cell.
THINGS TO REMEMBER
Solvation
Percent Composition by Mass
Mole Fraction
Molarity
Molality
Normality
Dilution