DETAILED PROJECT..!

1. Osmosis Project
What is Osmosis?
Osmosis is basically the movement of water molecules from a dilute system solution to a
concentrated solution, through a partially permeable membrane. Water molecules are able to
pass through the cell membrane because they diffuse whereas sugar molecules are larger and
cannot diffuse as easily therefore not being able to pass through. Cell membranes are like visking
tubes because they will let some substances through but not others. They are partially permeable
membranes.
Osmosis is a very important process which enables plants to support themselves by absorbing
water and minerals through a partially permeable membrane. Plants are often surrounded by a
film of water and a solution. Cell membranes often separate the two and Osmosis will occur. Hot
water diffuses and enters at a faster rate because there is more energy whereas cold water
enters at a slower rate because there is less energy.
What do we have to do?
To carry out the Osmosis project we have to measure the amount of water and solution that
enters carrot tissue through the partially permeable membrane. We will change the strengths of
the solution and then weigh the carrots to see
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Osmosis
Osmosis is thediffusion of a solventthrough asemipermeable membrane from a region of
low soluteconcentration to a region of high solute concentration. The semipermeable
membrane is permeable to the solvent, but not to the solute, resulting in achemical
potential difference across the membrane which drives the diffusion. That is, the solvent flows
from the side of the membrane where the solution is weakest to the side where it is strongest,
until the solution on both sides of the membrane is the same strength (that is, until
thechemical potential is equal on both sides).
Osmosis is an important topic in biology because it provides the primary means by
which water is transported into and out of cells.
Contents [hide]
1 Explanation
2 Example of osmosis
3 Chemical potential
4 Osmotic pressure
5 Reverse osmosis
6 See also
Explanation

2. Solutes, such as proteins or simple ions, dissolve in a solvent such as water. This raises the
concentration of the solute in these areas. The solvent then diffuses to these areas of higher
solute concentration to equalize the concentration of the solute throughout the solution.
Example of osmosis
A practical example of this osmosis in cells can be seen in red blood cells. These contain a high
concentration of solutes including salts and protein. When the cells are placed in solution,
water rushes in to the area of high solute concentration, bursting the cell.
Many plant cells do not burst in the same experiment. This is because the osmotic entry of
water is opposed and eventually equalled by the pressure exerted by the cell wall, creating
a steady state. In fact, osmotic pressure is the main cause of support in plant leaves.
When a plant cell is placed in a solution higher in solutes than inside the cell osmosis out of
the cell occurs. The water in the cell moves to an area higher in solute concentration, and the
cell shrinks and so becomes flaccid. This means the cell has become plasmolysed - the cell
membrane has completely left the cell wall due to lack of water pressure on it.
In unusual environments, osmosis can be very harmful to organisms. For example, freshwater
and saltwater aquarium fish placed in water with an different salt level (than they are adapted
to) will die quickly, and in the case of saltwater fish rather dramatically. In addition, the use of
table salt to kill leeches and slugs depends on osmosis.
Osmotic pressure
As mentioned before, osmosis can be opposed by increasing the pressure in the region of high
solute concentration with respect to that in the low solute concentration region. The force per
unit area required to prevent the passage of water through a semi-permeable membrane and
into a solution of greater concentration is equivalent to the osmotic pressure of the solution,
or turgor. Osmotic pressure is a colligative property, meaning that the property depends on
the concentration of the solute but not on its identity.
Increasing the pressure increases the chemical potential of the system in proportion to the
molar volume (δμ = δPV). Therefore, osmosis stops, when the increase in potential due to
pressure equals the potential decrease from Equation 1, i.e.:
Where δP is the osmotic pressure and V is the molar volume of the solvent.
For the case of very low solute concentrations, -ln(1-x2) ≈ x2 and Equation 2 can be
rearranged into the following expression for osmotic pressure:

3. Demonstrating with eggs
An egg contains a semipermeable membrane underneath the shell, which can be used to
demonstrate osmosis. The eggshell is mostly made ofcalcium carbonate which will dissolve in
acid. Vinegar or hydrochloric acidare suitable. Stronger acids will dissolve the shell faster, but
are more corrosive. Vinegar takes several days.
Method
• Place three eggs in a beaker, cover them with acid and weigh them down so they don't
float above the surface.
• Allow them to remain in the acid until the shells completely dissolve.
• Then place each of the eggs in a different liquid:
o Place one in water
o Place one in an isotonic sucrose solution, [about 0.3M]
o Place one in a 1M sucrose solution
• Leave overnight.
• The next day remove the eggs and compare their size.
You will find that the egg in water will have swollen considerably. If you carefully pierce the
membrane with a needle a jet of water will shoot into the air. The egg in an isotonic solution
will be approximately the same size, while the egg in 1M solution will have shrunk.
Demonstrating osmosis with Potato slices
There are a number of variations on this demonstration. Potato slices can be used, as also can
raw potato 'chips' (English) or 'French fries' (American). Consistancy of sample can be ensured
by using a commercial potato chipper, or by using a cork borer of selected diameter. Other
vegetables or fruit may, of course, be used. The changing dependent variable may be weight
or length.
Materials
• Potato
• Knife, cork borer, commercial chipper
• Cutting board
• Dilutions of sugar (sucrose), suggested range 0 - 0.6M
• Suitable containers (beakers or test tubes or potato cylinders) to match selected
dilution range
• Weighing balance / millimetre ruler
• Paper towel
• Marking pen/crayon
• Forceps
Note: Ensure that the cork borer or chipper will cut chips or cylinders which fit into a
standard test tube

4. Method
• Cut suitably sized slices or cylinders of potato. As far as is practical, all pieces should
be the same length, width, and thickness, the actual size depending on the chosen
container (beaker or test tube).
• Mark each container, pour in the appropriate dilution of sucrose.
• Pat each piece of potato dry, and a) weigh it or b) measure its longest length. Note
the measurement.
• When the piece has been measured, immerse it in one of your solutions.
• Leave the potato in the sugar solutions for at least half an hour.
• Use the forceps take out each chip in turn, carefully blot it dry without squeezing, and
remeasure the piece.
• Plot a graph of either absolute change or percentage change in weight/length v
molarity of the sugar dilution
Turgor
(Redirected fromOsmotic pressure)
Turgor (also called turgor pressure orosmotic pressure) is the pressure that can build in a
space that is enclosed by amembrane that ispermeable to a solvent such as water but not to
solutes.
A biological cell, for example a plant cell, contains ions, sugars, amino acids, and other
substances. In a hypotonic environment, water flows across the plasma membrane into the
cell (since the concentration of water is lower inside the cell than outside), causing it to
expand. The cell wall of a plant cell restricts the expansion, causing the cell to press against
the wall. The resulting pressure is called turgor.
The osmotic pressure π of a dilute solution can be calculated using the formula
where
M is the molarity
R is the molar gas constant
T is absolute temperature (i.e. measured in kelvin).
Examples of osmotic pressure
• Hypertonic is a solution with higher solute concentration (higher osmotic pressure)
than another thus water wants to move in.
• Hypotonic is a solution with lower solute concentration (lower osmotic pressure) than
another thus water wants to move out of it.
• Isotonic is solution with the same solute concentration (same osmotic pressure) as
another; no net movement of water.

5. Calculating Osmotic Pressure
Osmotic Pressure
We need to know the molar concentration of dissolved species in order
to calculate the osmotic pressure of an aqueous solution. We calculate
the osmotic pressure, (pi), using the following equation:
Where:
M is the molar concentration of dissolved species (units of mol/L).
R is the ideal gas constant (0.08206 L atm mol-1
K-1
, or other values
depending on the pressure units).
T is the temperature on the Kelvin scale.
π = MRTi
π =.01082 atm
R=0.082058 L-atm/mol-K
T=25+273= 298
i = 1 if the protein does not break up in solution and remains in 1 piece?
substituting in th eosmotic pressure equation we get
Molality = .01082 / ( .082058 X 298)
= 0.000442476 moles/ Kg
our solution is 4.3g / .29 l or 4.3 X 1 / .29 = 14.83 g / liter
if we assume density = 1 we also have 14.83 g of protein / kg of solution
comparing the descriptions of 1 kg of the solution we have .0004425 moles = 14.83 g

6. 1 mole weighs 14.83 / .0004425 = 33514 g/ mole !!
Snapshots 1–3: determining molecular weights for three different solutes
I. Osmotic Pressure via an Internal Measurement
Mechanism
Normallly when doing dialysis one fills the tube as full as possible so as to have the
greatest surface are for osmosis. The process will thus occur as rapidly as possible.
Afterall, osmosis is not an overly fast process in the first place!
When the contents are hypertonic, the tube becomes pressurized. In order to measure
that osmotic pressure, or turgor pressure, one is wont to think about affixing a manometer
or other pressure gauge to the system. But how can one do that and yet maintain of tight
seal that can withstand the expected pressures? Thus we move from science to
technology!
However, if one were to fill the tube only one third full with a large balloon of trapped air
above it, a barometer of sorts is created because that air is compressible (see left figure
to the right). The higher the osmolarity, the more water will try to flow into the tube, the
liquid volume expands and that compresses the trapped air. All one needs to do is note
the amount of that compression, which is quite easy since the tube is a cylinder and ruler
measurements are not difficult to make.
So much for the theory of this technology. Let us now turn to making it happen - the tricks
of the trade, as it were.
1. Make up a hypertonic solution. Table sugar is inexpensive and can form 40%
solutions. However, because it is a small molecule, it will slowly drop in
concentration as osmosis continues. It would be better to use something like
PEG (polyethylene glycol; aka "carbowax") having such a high molecular that it
cannot escape the tubing.

7. 2. How to entrap so much air in the tubing. After pouring in the desired amount of
hypertonic solution, blow a stream of air down into the tube, and then close the
very mouth of the tube. By spinning the tube around by the bottom end, a twist in
the tubing works its way down such that the trapped air fills out the "balloon." Do
not twist so much as to start compressing the air. All you want is to have the air
take the wrinkles out of the tube. Now tie your knot and work that knot down to
bottom of the twist, and pull the knot tight.
3. The tube at this time might still be a bit limp. Using a few turns of a string around
and around the tube well below the meniscus, tighten the string so the tube is
just barely rigid, and tie the string.
4. It helps to keep the whole dialysis "sausage" submerged so that the upper part
does not dry out and become brittle. There are two ways to keep the "sausage"
totally submerged:
a. tie two heavy lead fishing "sinkers" to each end of the sausage
b. take a long container (perhaps a flower vase), fill it with water by
submerging it horizontally in a bucket and then inserting the sausage into
it. Now lift the bottom of the "vase" and stand it up in the bucket. You will
see the trapped sausage bumping its "head" upon the bottom of the
completely filled vase.
Your system is ready to use, after you make two measurements:
a. In millimeters, measure and record the distance between the top and bottom knots in the
tubing. This measurement will later be used to adjust for the elasticity of the tubing as pressure
increases and the tubing stretches.
b. In millimeters, measure and record the distance between the top knot and the meniscus.
This measurement corresponds to the starting volume of the trapped air at one atmosphere of
pressure.
Using this simple apparatus, there are now two approaches to determining osmotic
pressure.
i. One is simply to immerse the tube in water and follow the compression of the trapped air
(above figure). The problem with this is that the concentration of the liquid inside the tubing is
continuously being diluted with water as the run proceeds. Only when the compression ceases
can one then determine to concentration of solute that brought about that amount of
compression. Often the solutes have no simple method for quantitation.
ii. Another approach (right) is to compress the trapped air a known amount by adding more
belts around the bottom portion of the tubing (below the meniscus). When this pressurized
system is immersed in water, and the meniscus neither rises nor falls, then the osmotic pressure
is known WITHOUT changing the concentration. But this will require a number of trials, as one
might try a series of set-ups each at a different pre-pressurization. Then one looks for the tube
with "no change."
Calculation:
Pressure = (To/Tx) x (Bo/Bx) x 14.2 psi
Atm pressure x 14.2 = psi (pounds per square inch)

8. Isotonic solutions are ones that contain a solvent, such as water,
and a solute, such as table salt. The ions of salt have an ionic bond, sodium plus chloride.
A saline solution is therefore considered isotonic.
Normal saline solution (0.9% NaCl) is considered isotonic with blood (although it
actually has a slightly higher degree of osmolality). Ringers lactate is also considered
isotonic.
5% Dextrose solution is also considered hypotonic compared with blood, because
although it is isotonic while infusing, the dextrose is metabolized and free water is left,
which is hypotonic.
In the general sense, two solutions are isotonic when they contain the same amounts of
solutes, or dissolved substances, and therefore have the same osmotic pressure. As
commonly used in the medical field, though, isotonic solutions are solutions which have the
sameconcentration of solute as the cells in the human body. A cell placed in
an isotonic solution will neither gain nor lose water.
When two aqueous solutions of different concentrations or tonicities are separated by a
semi-permeable membrane such as a cell wall, water will migrate from the less
concentrated, or hypotonic, side to the more concentrated, or hypertonic, side in an attempt
to bring both sides into equilibrium. This process is known as osmosis. The greater the
difference in the two solutions' concentrations, the higher the osmotic pressure will be, and
the quicker the osmotic transfer will be. It is the nature of osmosis that the identity of the
solute doesn't matter. Thus, salts, sugars, and other soluble compounds are all effective at
regulating osmotic pressure. All may be used to prepare isotonicsolutions.
Tonicity is of critical importance in biology and medicine because of its effect on living cells.
Cells will only grow in isotonic solutions, and any drug administered intravenously must be
adjusted to be effectivelyisotonic with human blood. A 0.9% solution of sodium chloride is
considered isotonic with blood, although in fact its osmotic pressure is actually slightly
higher.
Hypertonic soln.
A solution on which the concentration of solutes is greater than that of the cell that resided
on the solution
In healthcare you will often hear the words iso- and hypertonic solutions. A third option the
"hypotonic" solution is also a possbility.
As many people will know, the human blood contains both sodium, potassium, chloride salts.
In healthcare a solution will be hypertonic when the amount of salts in it exceeds that of
human blood. It will be isotonic (iso meaning "same") when the amount of salts are
comparable to that of blood. Finally the solution will be considered hypotonic when the
amount of salts present in the solution is less than that of blood.
Hypertonic: More concentrated

9. Isotonic: Just as concentrated
Hypotonic: Less as concentrated
The stiffness of plant
stems, roots, and leaves is due to the presence of water in their cells. Plants
exhibit turgor when they stand erect and return to their original position after
being bent This rigidity in plants is the result of the firmness of each water-filled
cell.
In this project, you will determine the changes in turgor pressure in plants as a
result of increases and decreases of water concentration in a plant's cells.
Factors affecting the absorption of water into cells, such as variations in cell
types, temperature, and permeability of the cell membrane, will be determined.
You will also study the effect of turgor pressure on plant movement

10. Getting Started
Purpose: To demonstrate the effects of turgor pressure on an animal cell
membrane.
Materials
• Baby food jar
• White vinegar
• Raw egg in shell
• Refrigerator
• 1-cup (250-ml) measuring cup
• Distilled water
CAUTION: Always wash your hands after touching an uncooked egg. It may
contain harmful bacteria.
Procedure
1. Fill the jar with vinegar.
2. Stand the egg in the jar of vinegar with the small end of the egg below the surface of the
vinegar (see Figure 7.1).
3. Put the jar and the egg in the refrigerator to prevent the egg from spoiling.
4. After 24 hours, remove the egg and discard the vinegar.
5. Carefully place the egg into the measuring cup without cracking the eggshell.
6. Fill the cup with distilled water.

11. 7. Put the cup in the refrigerator.
8. Observe the egg for seven days.
Results
The membrane exposed by the vinegar swells and finally ruptures. Cracks in the
shell starting at the edge of the exposed membrane form and extend across the
egg. (See Figure 7.2.)
Why?
The egg is a single cell surrounded by a cell membrane. This membrane—the
shell membrane—surrounds and controls the passage of materials into and out of
the egg.
Membranes that are selective in what passes through them are called
semipermeable membranes. Pores in the membranes are large enough to allow
the easy passage of water molecules, but they are too small to allow larger
molecules such as fats and proteins to get through. The movement of water
through a cell membrane is called osmosis and occurs when there is a difference
in the concentration of water on either side of the membrane.
The swollen shell membrane ruptures when placed into a hypotonic solution (a
solution with a higher water concentration than that of the area to which it is
compared). The water in the cup (100% water) is hypotonic to the fluid content
of the egg. As more water moves into the egg through the membrane, the cell
becomes crowded with excess molecules, which results in a buildup of pressure.
This pressure caused by excess water is called turgor pressure. As the fluid
content of the egg continues to increase, the pressure of the expanding shell
membrane breaks the hard eggshell. The thin, unprotective shell membrane
stretches under the pressure, creating a bulge that ultimately ruptures.

12. Try New Approaches
1. How do the results change when the egg is placed into a hypertonic solution (a solution with a
lower water concentration than that of the area to which it is compared)? Repeat the experiment
replacing the distilled water with a salt solution made with 1 cup (250 ml) of water and 1
tablespoon (15 ml) of table salt (sodium chloride). Science Fair Hint: Use a data table to
record written descriptions and diagrams of observations made of eggs placed into hypertonic
and hypotonic solutions.
2. If more of the membrane is exposed, does the egg continue to swell and rupture when placed
into a hypotonic solution? Repeat the original experiment removing the entire shell from the
egg by covering the egg with white vinegar for 24 hours. Measure the circumference of the egg
before placing it into the vinegar (mixture of acetic acid and water) and before placing it into
the water. After placing it in the water, measure it daily for seven days or until the egg breaks
(if it does). Use these measurements to determine the change in size of the cell due to osmosis
and whether the water continues to enter the cell at an even rate each day.

13. Each of these examples use cells, but the concept applies to other things (like water balloons,
etc.):