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6 years ago

I was looking for answers to PhysioEx Exercise 1.  I do not see any questions or answers for the complete exercise.
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5 Replies
Trusted Member
6 years ago
They only answer specific questions (i.e. activity 5) or (i.e. Review question 1-3)...

Start off by mentioning what the lab is called because it varies from edition to edition.
Answer accepted by topic starter
6 years ago Edited: 6 years ago, lws
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Lab 1 – Cell Transport Mechanisms and Permeability   (p. 1)
Activity 1: Simulating Dialysis (Simple Diffusion)
1-3: If the solution in the left beaker contained both urea and albumin, which membrane(s) could you choose to selectively remove the urea from the solution in the left beaker?

How would you carry out this experiment?

Activity 2: Simulating Facilitated Diffusion:

2-2: What do you think would happen to the transport rate if you put the same concentration of glucose into both beakers instead of deionized water in the right beaker?
1-4: Assume that the solution in the left beaker contained NaCl in addition to the urea and albumin. How could you set up an experiment so you removed the urea, but left the NaCl concentration unchanged? Hint: Assume that you also have control of the contents in the right beaker. 

Activity 4: Simulating Filtration:

4-1: How did the membrane's MWCO affect the filtration rate? A smaller membrane MWCO (size) causes _______________ (less, more, equal - choose one) filtration rate than a larger membrane MWCO.

4-2: Which solute did not appear in the filtrate using any of the membranes?

4-3: What would happen if you increased the driving pressure? Use the simulation to arrive at an answer. When I increased the driving pressure, filtration _______________ (increased, decreased, stayed the same - choose one).

4-4: Explain how you can increase the filtration rate through living membranes.

4-5: By examining filtration results, we can predict that the molecular weight of glucose must be greater than ____________ but less than _______________. (Hint: answer refers to solutes and NOT MWCOs).

Activity 5: Simulating Active Transport

5-1: Watch the solute concentration windows at the side of each beaker for any changes in Na+ and K+ concentrations. The Na+ transport rate stops before transport has completed. Why do you think that this happens? Hint: think about what is necessary for active transport to occur.

5-2: What would happen if you did not dispense any ATP?

5-3: Has the amount of Na+ transported changed?

5-4: What would happen if you decreased the number of sodium-potassium pumps?

5-5: Explain how you could show that this phenomenon is not just simple diffusion. (Hint: Adjust the Na+ concentration in the right beaker).

5-6: Is Na+ transport affected by this change? Explain your answer.

5-7: What would happen to the rate of ion transport if we increased the number of sodium-potassium pump proteins? 

5-8: Would Na+ and K+ transport change if we added glucose solution? 
Staff Member
6 years ago
I will provide you answers for activity 1 and 2, but the rest you're on your own because your activity level is low.

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.
- Master of Science in Biology
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6 years ago
Simple Diffusion
Activity 1: Simulating Simple diffusion

      1.What is the molecular weight of Na+? 22.9
      2. What is the molecular weight of Cl-? 35.45
      3. Which MWCO dialysis membranes allowed both of these ions through? 50, 100, and 200
      4. Which materials diffused from the left beaker to the right beaker? Urea, NaCl and glucose diffused
        5. Which did not? Why? Albumin, because the molecular weight exceeded the highest MWCO membrane, thus being to large to pass through

Activity 2: Simulating Dialysis

      1. What happens to the urea concentration in the left beaker (the patient)? It is reduced to 50% travels to the right beaker and reaches equilibrium at 17 minutes
      2. Why does this occur? Because the more concentrated it became it causes the molecules to move down

Facilitated Diffusion
Activity 3: Facilitated Diffusion
      1. At a given glucose concentration, how does the amount of time it takes to reach equilibrium change with the number of carriers used to “build” the membranes? The higher number of carriers the quicker it reaches equilibrium
      2. Does the diffusion rate of Na+/Cl- change with the number of receptors? No
      3. What is the mechanism of the Na+/Cl- transport? Plasma vessels
Look at #2 above; it’s simple diffusion because there is no change in diffusion rate with the number of receptors. The glucose that’s actively transported not the salt. If it did the amount of NaCl transported would increase with the number of receptors. The receptors are specific for glucose. -2.5pts

      4. If you put the same amount of glucose in the right beaker as in the left, would you be able to observe       any diffusion? No
      5. Does being unable to observe diffusion necessarily mean that diffusion is not taking place? No

Activity 4: Osmosis

      1.  Did you observe any pressure changes during the experiment? If so, in which beaker(s), and with which membranes? Yes in the Left beaker with the 20 MWCO Membrane because the pressure went up
      2. Why? Because no diffusion took place
      3. Did the Na+/Cl-diffuse from the left beaker to the right beaker? If so, with which membrane(s)? Yes, 50,100, and 200 MWCO
      4. Why? Because diffusion took place
      5. Explain the relationship between solute concentration and osmotic pressure?  They are directly proportional, if the solute concentration increases the osmotic pressure will increase.
      6. Does diffusion allow osmotic pressure to be generated?  No
      7. Would pressure be generated if solute concentrations were equal on both sides of the membrane? No it does not generate
      8. Why or why not? They are isotonic, they do not contribute to the tonicity of a solution as they pass through
      9. Would pressure be generated if you had 9 mM glucose on one side of a 200 MWCO membrane and 9 mM NaCl on the other side? If so, which solution was generating the pressure? No
 10. Would pressure be generated if you had 9 mM albumin on one side of a 200 MWCO membrane and 9 mM NaCl on the other side? If so, which solution was generating the pressure? Yes the albumin

Activity 5: Filtration

      1. What were the results of your initial membrane analysis? The concentration in filtrate was 0 for all and the membrane residue analysis showed all were present
      2. Does the membrane MWCO affect filtration rate? Yes
      3. Does the amount of pressure applied affect the filtration rate? No
      4. Did all solutes pass through all the membranes? There were traces of the powdered charcoal on the residue analysis, but the charcoal did not show up on the concentration I would have to say yes and no
      5. If not, which one(s) did not? Charcoal
      6. Why? The sizes of the pores
      7. How can the body selectively increase the filtration rate of a given organ or organ system? By increasing blood vessel radius to increase fluid flow and thus pressure in the vessel going to a given organ

Active Transport
Activity 6:Active Transport

      1. At the end of this experimental run, did the Na+/Cl- move from the left vessel to the right vessel? No
      2. Why?  No potassium present
      3. As the run progresses, the concentrations of the solutes will change in the windows next to the two beakers. The rate will slow down markedly, then stop before completed. Why? The rate of Active Transport decreases
      4. Does the amount of NaCl/KCl transported change? Yes
      5. Does the amount of solute transported across the membrane change with an increase in carriers or pumps? Yes
      6. Is one solute more affected than the other? No both are equal
      7. Does the membrane you “built” allow simple diffusion? Yes
      8. If you placed 9 mM NaCl on one side of the membrane and 15 mM on the other side, would there be movement of the NaCl? Why? No because like in #2 above there is no potassium present. The Na+/K+ pump requires both a sodium and potassium presence on opposite sides of the membrane
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6 years ago
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