Cell biology Lab.6

The diffusion of water across a
differentially permeable membrane has
been given a special name it is called,
Osmosis , Osmotic pressure develop on
all side of the membrane that has the
higher solute concentration.
Tonicity refers to the strength of a solution in relationship to
Osmosis, cells can be placed in solution that have the same
percentage of solute (isotonic solution), a higher percentage
of solute (hypertonic-solution),or a lower percentage of
solute (hypotonic solution ),that the cell.
-In the laboratory, cells are normally placed in solution that
causes them neither to gain nor to lose water. Such a solution
is said to be an isotonic solution, that is, the solute
concentration is the same on both sides of the membrane,
and therefore there is no net gain or loss of water.
The prefix iso means the same as and the term
tonicity refers to the strength of the solution . A
0.9% solution of the salt sodium chloride NaCl is
known to be isotonic to red blood cells because the
cell neither swell nor shrink when placed in this
-Any concentration of salt solution lower than 0.9%
is hypotonic to red blood cells. The prefix hypo
means less than
Red blood cell placed in such a solution expand and
sometimes burst due to the buildup of pressure caused
by the inward movement of water. The term lysis is used
to refer to disrupted cells, heamolysis, then process of
red blood cells.
Solutions that cause cells to shrink or to shrivel due to a
loose of water are said to be hypertonic solution. The
prefix hyper means more than and refers to a solution
with a higher percentage of solute (less-water) than the
A 10% solution of Nacl is hypertonic to red
blood cells. If red blood cells placed in this
solution, they shrink. The term crenation
refers to red blood cells in this condition.
A-No net movement of water cell
water enters the cell
water exits the cell
After preparing the 3 solutions ; hypertonic , isotonic
and hypotonic solution , then we mix the blood with
each one of these solutions in a tube and left stand for 30
- 45 minutes .After that the blood is examined for these
changes by making blood smear :By putting a small drop of blood on the slide and by
using another clean slide as a “spreader”, touch the small
drop with the spreader and allow the blood to run along
its edge. away from the largest drops, keeping the
spreader at an angle of 45°.
Allows the smear to dry in a flat level position protected
from flies, dust, external heat. Put an oil and examine
under oil immersion .
Hypertonic solution : the blood cells will shrink.(
Isotonic solution : the blood cells will not change.
Hypotonic solution : the blood cells will swell , burst
and lysis.