Your lab group is experimenting with the diffusion of molecules across a membrane. Dialysis tubing is used as a model cell membrane because is it semi-permeable, allowing small molecules to cross the membrane, but NOT larger molecules, like starch. A starch solution is placed in the dialysis tubing and then the dialysis tubing is placed in an iodine and water solution. Iodine is used as an indicator for the presence of starch. Normally, iodine is a yellow-brown color (on the left), but in the presence of starch, it turns a deep purple (right). After observing the experimental setup for 20 minutes, the iodine solution remains brown, but the starch solution inside the dialysis tubing is purple and swollen. What CANNOT be concluded from the results?
A] Iodine is a small molecule and diffused through the dialysis tubing INTO the starch solution.
B) Starch is a large molecule and could NOT diffuse through the dialysis tubing into the iodine solution.
C) Starch requires ATP energy for transport and therefore cannot cross the dialysis tubing into the iodine solution.
D) The starch solution is hypertonic to the iodine solution, causing water to move across the dialysis tubing INTO the starch solution.
C) Starch requires ATP energy for transport and therefore cannot cross the dialysis tubing into the iodine solution.
The statement that cannot be concluded from the results is:
C) Starch requires ATP energy for transport and therefore cannot cross the dialysis tubing into the iodine solution.
This conclusion cannot be drawn from the given results because the experiment does not provide any information about the energy requirements for starch transport.
To determine which statement cannot be concluded from the results, we need to analyze each statement in relation to the observations made.
A) Iodine is a small molecule and diffused through the dialysis tubing INTO the starch solution.
This statement suggests that iodine molecules, being small, were able to cross the dialysis membrane and enter the starch solution. This conclusion is supported by the observation that the starch solution inside the dialysis tubing turned purple, indicating the presence of starch.
B) Starch is a large molecule and could NOT diffuse through the dialysis tubing into the iodine solution.
This statement suggests that starch molecules, being larger, would not be able to cross the dialysis membrane and enter the iodine solution. This conclusion is supported by the observation that the iodine solution remained brown, indicating the absence of starch.
C) Starch requires ATP energy for transport and therefore cannot cross the dialysis tubing into the iodine solution.
This statement suggests that the transport of starch requires energy in the form of ATP, preventing it from crossing the dialysis membrane. However, the observation that the starch solution turned purple suggests that starch did cross the membrane.
D) The starch solution is hypertonic to the iodine solution, causing water to move across the dialysis tubing INTO the starch solution.
This statement suggests that the difference in solute concentrations between the starch solution and the iodine solution caused water to move across the membrane into the starch solution. The observation of the swollen starch solution is consistent with the movement of water into the solution.
Based on the observations, the statement that cannot be concluded from the results is:
C) Starch requires ATP energy for transport and therefore cannot cross the dialysis tubing into the iodine solution.
This conclusion is not supported by the observation that the starch solution turned purple. The movement of starch into the iodine solution suggests that it was able to cross the dialysis membrane without the need for ATP energy.