GUIDED DIFFUSION LAB QUESTIONS & ANSWERS 1. Why are celery sticks soaked in saltwater more flexible than those soaked in plain water? Plain water is hypotonic to the inside of the cells, so water flows into the cell and expands, increasing turgor pressure. Salt is hypertonic to the inside of the cells, so cells become shrunken relative to the cell wall, and turgor pressure is decreased. 2.
Examine your data from Part 1A: Guided Inquiry. What dimensions supported the fastest diffusion rate? Why? The diffusion rate in this experiment is constant because the concentration of solute is constant. 3.
What dimensions supported the greatest diffusion percent total volume? Why? The greatest surface to volume ration causes he biggest change in g total volume. Construct a useful graph of the relationship between cell dimension to the extent of diffusion. Surface area/volume 4.
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Why can’t humans drink seawater for hydration? Explain. Seawater is hypertonic to digestive system cells. Therefore, water will be drawn out of the cells to be excreted. 6.
Examine the initial and final weights of the model cells. What cause the mass of the dialysis bags to change? Was there more or less water in the dialysis bags at the conclusion of the experiment? Explain. Answers will vary, but the students should account for the change in mass to the water entering and leaving the model cell. Students should conclude which solutions have the greatest and least water potential inside and outside of the model cell. 7.
From your results, which solutes, if any, diffused across the membrane and which, if any, were restricted? Why do you think this occurred? Protein is restricted since its concentration does not drive water either way. Protein is much larger than simple molecules, and will not pass through the pores of the membrane. 8.
How is dialysis tubing different from a cell membrane? Answers will vary. They may include: Dialysis tubing is much less complex; it is not a lipid bilayer; it does not use energy to pump materials against a concentration gradient. 9.
Which color mystery solution had the highest concentration of sucrose? How do you know this? The pink mystery solution had the highest concentration of sucrose, since the core weighed the least at the end of the 30 minutes.