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.