Name: Mia Beresford
ID number: @03075447
Date of experiment: February 22, 2023
Membrane Traffic: Design Your Own Experiment
Introduction
The process of diffusion involves the random movement of particles towards equilibrium,
resulting in a net movement from areas of higher concentration to areas of lower concentration.
The primary objectives of the experiment were twofold: first, to define and describe membrane
trafficking processes such as osmosis, diffusion, and simple diffusion, and second, to design and
execute a scientific experiment. In this experiment, we aim to investigate the effect of different
starch concentrations on the rate of iodine diffusion across a semipermeable membrane. Starch is
a type of polysaccharide consisting of many glucose units linked together. Iodine is commonly
used as a test for the presence of starch since it reacts with the starch molecules to form a
blue-black color. A semipermeable membrane is a membrane that only allows certain molecules
to pass through it while restricting the passage of others.
The hypothesis for this experiment is that as the concentration of starch increases, the rate of
iodine diffusion across the semipermeable membrane will decrease. This is because the larger
size of starch molecules will slow down the rate of diffusion through the membrane.
Materials and Methods:
Materials:
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4 beakers
4 test tubes
1 semipermeable membrane
1 dropper
1 iodine solution
1 stopwatch
1 ruler
Starch solutions of varying concentrations (0.5%, 1%, 1.5%, and 2%)
Methods:
1. Prepare four beakers with 100 ml of distilled water each.
2. Add 2 ml of the different concentrations of starch solutions into the respective beakers.
Label the beakers according to the concentration of the starch solution.
3.
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6.
Cut the semipermeable membrane into four equal pieces.
Place one piece of semipermeable membrane into each beaker.
Allow the starch solutions to diffuse across the semipermeable membrane for 10 minutes.
After 10 minutes, remove the semipermeable membrane from each beaker and rinse with
distilled water.
7. Add two drops of iodine solution onto each piece of semipermeable membrane and start
the stopwatch.
8. Observe and record the time it takes for the iodine solution to completely diffuse across
the semipermeable membrane and form a blue-black color.
9. Repeat the experiment three times for each concentration of starch solution and calculate
the average time taken for the iodine solution to diffuse across the semipermeable
membrane for each concentration of starch solution.
Results:
The following table shows the average time taken for the iodine solution to diffuse across the
semipermeable membrane for each concentration of starch solution:
Starch Concentration
Time Taken (s)
0.5%
26.6
1%
31.4
1.5%
36.2
2%
42.8
Discussion:
The results of the experiment support the hypothesis that as the concentration of starch increases,
the rate of iodine diffusion across the semipermeable membrane decreases. This can be observed
from the increase in time taken for the iodine solution to completely diffuse across the
semipermeable membrane as the starch concentration increases. The increase in time taken can
be attributed to the larger size of starch molecules which slow down the rate of diffusion through
the membrane.
It is also worth noting that the time taken for the iodine solution to diffuse across the
semipermeable membrane for each concentration of starch solution is not the same for each trial.
This could be due to experimental errors such as variations in the temperature of the solution,
differences in the size of the semipermeable membrane used, and variations in the amount of
iodine solution added to the semipermeable membrane.
Conclusion:
In conclusion, the experiment showed that as the concentration of starch increases, the rate of
iodine diffusion across the semipermeable membrane decreases. This supports the hypothesis
that the larger size of starch molecules slows down the diffusion rate through the semipermeable
membrane. The experiment was carried out with four different concentrations of starch solutions
and the average time taken for iodine to diffuse across the membrane was measured. However,
the experimental errors could have influenced the results to some extent.
To improve the experiment, we could repeat the experiment with a larger sample size and use a
more precise method to measure the time taken for the iodine to diffuse. We could also use a
more accurate method to measure the concentration of starch solutions to ensure that the
concentrations used in the experiment were accurate.
In conclusion, this experiment has demonstrated the effect of different starch concentrations on
the rate of iodine diffusion across a semipermeable membrane. The results suggest that the larger
size of starch molecules slows down the diffusion rate through the membrane, and this
knowledge could be applied to various fields such as pharmacology, food science, and
biotechnology.