Effect of temp on membranes

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Effect of temperature on the
movement of pigment through
cell membranes
Using beetroot and a colorimeter
Introduction
• In beetroot cells the red anthocyanin pigment
occurs in the vacuoles. Each vacuole is
surrounded by a tonoplast membrane and
outside it, the cytoplasm is surrounded by the
plasma membrane.
• We can draw certain conclusions about these
membranes by studying their properties.
• In this practical we shall see how temperature
affects the rate at which the anthocyanin
pigment leaves the cells.
Procedure
• Heat 200 ml of distilled water to 85oC.
• Whilst the water is heating, using a syringe
place 10 ml of distilled water into each of ten
tubes. Label the tubes 85, 80, 75, 70, 65, 63,
60, 55, 50 and 45.
• Remove a cylinder of beetroot tissue using the
narrow cork borer.
• Cut a total of 10 beetroot cylinders each with a
length of 3cm.
Procedure continued
• Place a beetroot cylinder in the beaker of water
at 85oC for one minute.
• After one minute remove with forceps and
transfer to the test tube of cold water labelled
85oC.
• As the distilled water in the beaker cools repeat
the previous two steps, using a fresh cylinder
each time, at the following temperatures 80oC,
75oC, 70oC, 65oC, 63oC, 60oC, 55oC, 50oC and
45oC.
Procedure continued
• Leave each cylinder in its test tube of cold
water for exactly 30 minutes.
• After 30 minutes, shake the test tube and
remove the beetroot cylinder. At the end of the
experiment you should have ten test tubes
containing water which is stained red with
anthocyanin pigment.
• Using the colorimeter, compare the amounts of
red pigment which have diffused out of the
cylinders by measuring the absorbance of light
of 4ml of the stained water placed in a cuvette.
Design and Data Collection
1. Identify: (a) the dependent variable (b) the
independent variable (c) the controlled
variables in this investigation.
2. What would be the best way to record your
raw (unprocessed) data? Record your data in
this form.
3. What would be the best way to show
estimated errors/uncertainties in your raw
data. Include this with your recorded data.
Data processing and presentation
1. First decide if there any way your data could
be processed (changed) into a more useful or
informative format?
2. Present your data in a suitable form
(remember what the aim of the investigation is
in deciding on the best presentation).
3. Show your estimated errors/uncertainties on
your presented data.
Conclusion and Evaluation
1. State a conclusion based upon
interpretation of your data (include
justification).
2. Evaluate weaknesses and limitations of
the procedure.
3. Suggest realistic improvements in
respect of identified weaknesses and
limitations.
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