Effect of ethanol concentration on membrane permeability

Question 1

What is the IV/DV of this experiment?

Answer 1

IV: the (5 different) ethanol concentrations
DV: absorbance by beetroot (Au)

Question 2

Describe the set up of the test tubes

Answer 2

-label 5 test tubes with ethanol concentrations 0% 20% 40% 60% 80% 100%
-total volume for each is 5cm3
-water fills up the remainder of the tube (eg 20% would be 1cm3 ethanol and 4cm3 water)

Question 3

Describe the procedure

Answer 3

-trim 5 beetroot cylinders to same
-pour liquid into corresponding cuvette and make a blank using water
-use colorimeter with green filter to measure absorbance for each concentration and record, plot graph

Question 4

Considerations during experiment

Answer 4

-use knife and ruler to trim
-use forceps to remove cylinders
-absorbance measured in Au

Question 5

What are some control variables?

Answer 5

-same SA beetroot
-same ethanol volume
-same time that tubes are left
-same beetroot
-use of control group
-rinsing and blotting

Question 6

What is a limiting factor and how can it be rectified?

Answer 6

temperature- use water bath to thermostatically control

Question 7

What does reproducibility mean?

Answer 7

anyone can replicate the whole experiment

Question 8

What does repeatability mean?

Answer 8

students can do repeats of their results

Question 9

How can you prove repeatability and reproducibility?

Answer 9

-standardised procedure
-calculate mean
-use standard deviation
-exclude anomalies

Question 10

What type of results would you expect to find?

Answer 10

-as ethanol concentration increases, absorbance increases meaning the membrane is more permeable
-however after a certain point absorbance begins to decrease