6 A student investigates the process of passive transport by the cell

Question

membrane by creating a model. The student puts a starch solution in a
dialysis tubing bag. The bag is then placed in a beaker that contains an
iodine solution. The dialysis tubing bag is semipermeable. The student's
observations are in the table.
Part of System
Water and iodine
solution in beaker
Starch solution in
Observations
Observations Before Bag
Was Added to Beaker
Light yellow
Cloudy, white
dialysis tubing bag
Observations After Bag
Was Added to Beaker
Light yellow
Blue-black
The student concludes that the iodine passes through the dialysis tubing
material but the starch molecules cannot.
Which two statements provide evidence to support the student's
conclusion?
M. The starch solution turned blue-black after the bag was placed in the beaker.
P. The iodine solution did not change color after the bag was placed in the
beaker.
R. The iodine molecules passed through the bag because they are not the same
size as the starch molecules.
S. The starch solution did not react with the iodine solution after the bag was
placed in the beaker.
T. The change in color of the iodine solution was due to a student error in
procedure.

Answer 1

To support the student's conclusion that iodine can pass through the dialysis tubing while starch cannot, the following two statements provide the necessary evidence:

R. The iodine molecules passed through the bag because they are not the same size as the starch molecules.
This statement explains the mechanism of why iodine can pass through the membrane while starch, which is a larger molecule, cannot.

S. The starch solution did not react with the iodine solution after the bag was placed in the beaker.
This statement indicates that the starch remained inside the bag and did not interact with the iodine in the beaker, providing evidence that the starch did not leave the dialysis tubing bag.

The other options either do not support the conclusion or suggest errors rather than providing evidence for the student’s claim.