Answers to Questions
Activity 1: Simulating Dialysis (Simple Diffusion) (pp. 2–4) 9. All solutes except albumin are able to diffuse into the right beaker. Using distilled water in the right beaker and either the 100 MWCO or 200 MWCO membrane will remove urea from the left beaker and leave albumin If the left beaker contains NaCl, urea, and albumin, you can selectively remove urea by dispensing a concentration of NaCl into the right beaker equivalent to that in the left beaker and by using the 100 or 200 MWCO membrane. Albumin is too large to diffuse and there will be no net diffusion of NaCl. However, urea will move down its concentration gradient into the right beaker.
Activity 2: Simulating Facilitated Diffusion (pp. 4–5)
11. Carrier proteins facilitate the movement of solute molecules across semipermeable membranes, so increasing their number will increase the rate of diffusion.
Because facilitated diffusion requires a concentration gradient, making the concentration on both sides of the membrane equal stops net diffusion. NaCl does not have an effect on glucose diffusion.
Activity 3: Simulating Osmotic Pressure (pp. 6–7)
6. Using the 20 MWCO membrane results in an osmotic pressure increase using any of the solutes. The 50 and 100 MWCO membranes caused osmotic pressure increase with albumin and glucose. Only albumin caused osmotic pressure increase using the 200 MWCO membrane.
NaCl appeared in the right beaker with all membranes except the 20 MWCO membrane.
8. Increasing the number of non‐diffusible particles increases osmotic pressure. If solutes are able to diffuse, then equilibrium will be established and osmotic pressure will not be generated.
Osmotic pressure would be zero if albumin concentration was the same on both sides of the membrane.
If you increased (or doubled) the concentration of albumin, osmotic pressure will increase (or double).
Glucose is freely diffusible using the 200 MWCO membrane and therefore has no effect on osmotic...
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