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

Question

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 passes through the dialysis tubing while starch cannot, the following two statements provide evidence:

1. R. The iodine molecules passed through the bag because they are not the same size as the starch molecules. - This statement directly addresses the size difference between the two types of molecules, which explains why iodine can pass through the semipermeable dialysis tubing while starch cannot.

2. S. The starch solution did not react with the iodine solution after the bag was placed in the beaker. - This statement indicates that starch molecules remain inside the bag and did not interact with the iodine solution in the beaker, further supporting the conclusion that starch cannot pass through the dialysis tubing.

These two statements provide a coherent explanation of the observations made during the experiment, supporting the student’s conclusion.