Final answer:
The best representation of changes in a dialysis bag over time is that starch concentration remains constant due to its large size, while water concentration increases as water moves towards the higher concentration of solutes, and glucose concentration decreases as glucose molecules diffuse out of the dialysis bag.
Step-by-step explanation:
To answer the question regarding how molecular size affects movement through a membrane, we should assess the possible changes in the concentrations of three different substances within a dialysis bag: starch, water, and glucose. Dialysis is a process similar to osmosis where water, small molecules, and ions can pass through a dialyzing membrane, leaving behind larger molecules like starch. Considering this, and the information provided from various examples involving diffusion and osmosis, we can analyze the options given.
The most accurate prediction for the changes in concentrations within the dialysis bag over the course of an investigation is that the starch concentration will remain constant, given that starch molecules are too large to pass through the membrane. There would be no net movement of starch out of the dialysis bag. On the other hand, water concentration would likely increase in the bag because water moves toward the side with a higher concentration of solutes (starch and glucose) to reach equilibrium. Lastly, the glucose concentration would decrease because glucose molecules are small enough to pass through the membrane and would move from an area of high concentration inside the bag to an area of low concentration outside the bag.
Therefore, the answer that best represents the amount of starch, water, and glucose in the dialysis bag over time would be: starch concentration remains constant, water concentration increases, and glucose concentration decreases.