Cell Membrane
To study the effect of environmental changes in the permeability of
living beet
root cells. Procedure A: The effect of pH on the cell membrane
Materials &
Method 1. Cut a beet root into slices approximately 2mm
thick. Use a cork bore
to cut out thirty-five (35) slices. 2. Place the discs
in a 250 mL beaker and
rinse thoroughly in cool running tap water. The red
pigment collected comes from
the damaged cells and can be used to analyze the
chemical nature of the pigment.
3. The pigment in a beet, anthocynanin,
should be analyzed before beginning.
This can be done simply by first
adding a few drops if concentrated acid to a
sample if beet juice. 4. The
resulting solution can be compared to a second
sample made by adding a few
drops if concentrates base to another sample of beet
juice. Note the colours
of each. Given stock solutions of 0.1 mol/L HCl and 0.1
mol/L NaOH, and
graduated cylinders, prepare the following solutions in separate
test tubes.
a) 10 mL of 0.1 mol/L HCl b) 10 mL of 0.01 mol/L HCl c) 10 mL of
0.001
mol/L HCl d) 10 mL of distilled water e) 10 mL of 0.001 mol/L NaOH f) 10
mL
of 0.01 mol/L NaOH g) 10 mL of 0.1 mol/L of NaOH 5. Place five (5) beet
root
discs in each of the 7 test tubes. 6. Leave them for 15 minutes and then
record
your observations. Agitate gently and continue to observe them at
15-minute
intervals until no further changes occur. Procedure B: The effects
Of An Organic
Solvent Materials & Methods 1. Prepare beet root discs
as for Procedure A.
The number required will depend on the control you
design. 2. Place five (5) of
the discs in a test tube containing 10 mL of
distilled water and 2 mL of
ethanol. 3. Design a control for this
investigation. 4. Agitate gently and
periodically for 15 minutes and record
your observations. Observations:
Analyzing anthocynanin by adding
concentrated acid and base to beet juice
Mixture Observations recorded
Few drops of concentrated acid added to a sample
of beet juice -Concentrated
acid caused the anthocynanin to turn to a slightly
lighter shade of pink. Few
drops of concentrated vase added to a sample of beet
juice -Concentrated base
caused the anthocynanin to turn a transparent yellow.
Serial Dilution
Intervals 0.1 mol/L 0.01 0.001 Distilled` 0.001 0.01 0.1 HCl
mol/L mol/L
Water mol/L mol/L mol/L HCl HCl NaOH NaOH NaOH 15 -lots of -less
pigment -a
small -very little -a small -barely -a yellow Minutes pigment lost
lost than
the amount pigment lost amount any pigment is -solution is dark 0.1
solution
of from the beet of pigment present in purple in of HCl pigment root
pigment
lost the colour lost lost from the solution from the from the beet root
beet
root beet root 30 -slightly -slightly -slightly -slightly -slightly
-slightly
-slightly Minutes more more more more more more more Pigment pigment
pigment
pigment pigment pigment pigment lost since lost since lost lost since
lost
lost lost the the since the the since since since observation
observations
obser- observations the the the made at made at vations made at
observ- observ-
observ- 15 minutes 15 minutes made at 15 minutes ations
ations ations 15 made at
made at made at minutes 15 15 15 minutes minutes
minutes 45 -solution -solution
-solution -a darker shade -solution -solution
-the Minutes is dark is pink in is
a of pink than is a light is a light
mixture is purple in colour lighter the
0.001 pink pink very colour
throughout shade of solution of through- through-
yellow throughout pink HCl
but not out the out the throughout than that of the
mixture, mixture, the
actual the 0.01 0.01 solution similar similar beet have
solution of HCl to
that to that turned of HCl of the of the brown in 0.001 0.001
colour mol/L
mol/L HCl HCl The Effects Of An Organic Solvent: Designing A
Control The
control our group designed for this investigation was to have one
test tube
with 10 mL of distilled water 2 mL of ethanol. This way both test
tubes would
have a total of 12 mL and 5 beet roots each. Test tube with 12 mL of
water
Test tube with 10 mL of water and 2 mL of ethanol -very little pigment
lost
-light pink in colour -beets moved (twirled) when agitated -very
little
pigment lost -only a light tint of pink could be seen -beets did not
move when
agitated, they remained at the bottom of the test tube -traces of
oil were
present in the test tube Discussion 1. What relationship exists
between the
concentration of acid or base solution and the pH? In a solution,
pH refers to
the concentration of H+ ions. The pH is expressed as a positive
number while the
concentration of the H+ ions is taken in exponent form.
Bases start at as low as
10-14 and acids are up to 1. Therefore taking
the pH from the concentration is
determined by taking the negative value of
the exponent of hydrogen
concentration H+ 2. How is the membrane affected by
the different pH values of
the solutions? What changes have the tested
solutions created in the structure
of the membrane? The pH value of
Hydrochloric acid is 0, and the pH value of the
Sodium hydroxide is 14.
The acid caused the membrane to "tear" from the
damage caused by. The
anthocynanin then permeated through the membrane. Since
the pH value of the
distilled water is 7, which is neutral, caused no damage to
the cell
membrane. The closer the substance was to neutral the more osmosis
pressure
was create around the sell membrane. Once the cell was full with as
much
water as it could with hold, the osmosis pressure rises. The
Sodium
hydroxide’s pH intensity was so high that it caused the cell membrane
to
degrade, which made permeability increase. 3. At which pH does the
maximum
intensity of anthocynanin, occur? At which pH does the least occur?
The pH that
the maximum intensity of anthocynanin occurred at was at the 0.1
mol/L of HCl,
due to the high pH content and the low dilution of the
substance. The pH that
did the least amount of damage to the cell membrane
was the 0.001 mol/L of NaOH,
due to the low pH content and the dilution of
the substance. 4. Would you expect
similar results using carrot roots (which
contain an orange pigment)? Explain
your answer. The pigment of the carrot
cell is orange and would probably make it
more difficult to decipher between
the pH levels. While the beet root makes it
easier. At each different level
that the pH was diluted at, made the pink fluid
turn lighter, until the use
of NaOH then it slowly became more yellow. This
would be more difficult with
the carrot root. The membranes also differ quite a
bit. 5. Under what
circumstances would be of important to plants? Animals? If
the pH inside of a
cell, in a plant or animal is unbalanced and is either two
high or two low it
could cause destruction of damage top the cell which could
cause the cell to
die. The reaction to the beet root is a good example. 6.
Compare the test
tube with the organic solvent to the control, account for any
changes seen.
The two different test tubes differed in many ways. In the organic
the beets
stayed at the bottom while agitated, while the other test tube the
beets spun
around the tube when agitated. 7. Suggest how the ethanol has
affected the
cell membrane. Because both the water and the ethanol both have
hydrogen
bonds this could cause the beets to remain at the bottom of the test
tube.
When a polar solute, enters into water the water molecules surround
the
solute and it becomes no longer to diffuse through the membrane. 8. Would
all
organic solvents be likely to affect the permeability of the water
membrane the
same way? Explain. No, not all-organic substances would affect
the permeability
of the cell membrane, as the ethanol did. The non-polar
molecules would not go
also with the hydrophilic heads of the phospholipids.
As well as alkanes,
alkenes, and alkynes. Conclusion: A cell membrane reacts
differently to it’s
surrounding, which causes either a life or death
situation for the cell. A pH
with a very high, or a very low concentration,
will cause damage to the cell,
where a medium pH level will do very minimum
damage to the cell. When damage is
done to the cell, osmosis and diffusion
become easier for outside solutions.
When a cell reaches equilibrium
(with water) it creates osmosis pressure.
Osmosis pressure is when the
hydrostatic pressure from inside the cell is
greater then the pressure from
outside the cell. Organic solvents also affect
the permeability of the cell.
Ethanol is miscible with water and both posses
hydrogen bonds.