Required practical 4 - effect of temperature on beetroot cell - surface membranes

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Where are plant pigments stored?
In the vacuole (purple beetroot pigment is called betalain)
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What is used to cut the pieces of beetroot tissue?
A cork borer
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Why should the beetroot pieces all be the same size?
To ensure that all pieces have the same surface area (this must be a control variable as it affects the amount of space through which betalain can diffuse through the membrane)
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What is used to measure the amount of betalain that has left the beetroot cells?
A colorimeter (reads absorbance/transmission which can be compared with a calibration curve to deduce the concentrations of betalain for each temperature)
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Why does increasing the temperature cause an increase in the concentration of betalain in the water from the test tube?
The phospholipid bilayer structure becomes disrupted and channel proteins within the membrane become denatured, so pigment molecules are able to diffuse out of the cell through the membrane. Higher temp=more denaturation.
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What are the 5 controlled variables?
Volume of water in test tube (as this affects concentration of betalain), size (SA) of beetroot pieces, pH, length of time left in the test tube, beetroot that samples are taken from.
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Why does the graph eventually level off? (no change in absorbance after a certain temperature)
An equilibrium is reached between the concentrations of betalain inside and outside of the beetroot cells, so there is no net movement of betalain.
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Why must the beetroot discs be blotted dry before commencing the experiment?
So that any betalain already leaked from the membranes does not enter the water of the test tube and affect its concentration.
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Why must the test tubes be shaken every so often?
To prevent the beetroot disks from sticking to the side of the test tubes/each other as this would reduce their exposed surface area.
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Why should a control be set up? *
Increases validity of results by illustrating that differences for each temperature are due to temperature changes and not another factor.
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Other cards in this set

Card 2

Front

What is used to cut the pieces of beetroot tissue?

Back

A cork borer

Card 3

Front

Why should the beetroot pieces all be the same size?

Back

Preview of the front of card 3

Card 4

Front

What is used to measure the amount of betalain that has left the beetroot cells?

Back

Preview of the front of card 4

Card 5

Front

Why does increasing the temperature cause an increase in the concentration of betalain in the water from the test tube?

Back

Preview of the front of card 5
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