1. The molecular weight of urea is approximately 60. Which of the membranes can it pass through?
a. 50 MWCO membrane
b. 100 MWCO membrane
c. 200 MWCO membrane
d. Both the 100 and 200 MWCO membranes d
4. Describe two variables that affect the rate of diffusion.
The temperature of the solutions; the difference in concentration of the ion or molecule between the sides of the membrane; the molecular weight of the ion or molecule; the MWCO of the membrane
8. True or False: The facilitated diffusion of glucose requires energy from ATP.
FALSE; it is still passive diffusion
10. True or False: If there are a sufficient large number of transport proteins present, glucose can be transported from a solution of lower concentration to a solution of higher concentration (i.e. up its concentration gradient.)
FALSE; only active transport can move something “up” its concentration gradient
12. The larger value obtained when more glucose carriers were present corresponds to an increase in the rate of glucose transport. Explain why the rate increased.
With fewer carriers being present, they can become saturated; this will slow or stop the transport of glucose.
18. Describe one way in which osmosis is similar to simple diffusion; describe one way in which it is different.
Same: They are both passive processes; the ions or molecules can only pass down their concentration gradients.
Different: Osmosis, a special form of diffusion, is the diffusion of the solvent (e.g. water) through a selectively permeable membrane.
19. Solutes are sometimes measured in milliosmoles. Explain this statement: “Water chases milliosmoles.”
Osmosis is the diffusion of the solvent, e.g. water. The water in this simulation diffuses to the side of the membrane that has the highest concentration of the solutes.
22. True or False: The simulation would not function if the top beaker were open to the atmosphere instead of having pressure applied to the top beaker.
FALSE; atmospheric pressure would still allow filtration to occur
29. Describe the significance of using 9mM sodium chloride inside the cell and 6mM potassium chloride outside the cell.
Referring to Figure 3.9, page 51 of the text, you see that 3 Na+ ions are transported out of the cell and 2 K+ ions are transported into the cell. This ratio of 3:2 is the same as the ratio of 9mM:6mM
30. Explain why there was no sodium transport even though ATP was present.
In order for the Na+/K+ pump to function, both these ions and ATP must be present. In this simulation, no K+ was present.
32. Do you think glucose is being actively transported or transported by facilitated diffusion in this experiment. Why?
Glucose is being transported down its concentration gradient…by facilitated diffusion. No energy is required for this to happen.
I hope these help someone
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