Question

A student is investigating cellular transport and how it helps maintain homeostasis in living systems. The student completes the following steps:

Add 2 g of glucose and 2 g of starch to distilled water. Stir the mixture and pour it into a piece of dialysis tubing, which is used to represent the semipermeable cell membrane.
Seal both ends of the dialysis tubing, and rinse the outside of the tubing.
Place the dialysis tubing in a beaker of distilled water.
After 30 minutes, remove the dialysis tubing from the beaker.
Test for the presence of starch and glucose in the beaker and the dialysis tubing.
The student found that there was starch and glucose inside the dialysis tubing, while there was glucose but no starch inside the beaker.

Which of the following diagrams would be best for the student to include in his lab report to represent what occurred when the dialysis tubing was placed in the beaker?

A.
image

B.
image

C.
image

D.
image

Answer 1

C

Explanation: Dialysis tubing is semipermeable — small molecules like glucose can diffuse through the membrane into the beaker while large starch molecules cannot. The correct diagram shows small particles passing through the membrane (present both inside and outside) and large particles remaining only inside the tubing. This movement is passive diffusion (no energy required).