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E X E R C I S E
version 8
1
Cell Transport Mechanisms
and Permeability
Time Allotment: 2 hours minimum, 3 hours preferred.
Your computer should meet the following minimum requirements for PhysioEx 8.0:
WINDOWS
OS: Windows® XP, Vista™
Resolution: 1024 × 768
Latest version of Adobe® Flash® Player
Latest version of Adobe Reader®
Browsers: Internet Explorer 6.0 (XP only);
Internet Explorer 7.0; Firefox 2.0
Internet Connection: 56K modem minimum for
website
Printer
MACINTOSH
OS: 10.3.x, 10.4.x
Resolution: 1024 × 768
Latest version of Adobe Flash Player
Latest version of Adobe Reader
Browsers: Safari 1.3 (10.3.x only); Safari 2.0
(10.4.x only); Firefox 2.0
Internet Connection: 56K modem minimum for
website
Printer
Advance Preparation, Comments, and Pitfalls
1. If you are using PhysioEx in a computer lab: Because PhysioEx requires a browser
(such as Firefox or Internet Explorer) and the Flash Player to run, it is recommended
that you make sure these items are already installed on student computers before beginning this lab.
2. If you are using the web version of PhysioEx: Have your students go to
http://www.physioex.com and follow the registration instructions found in the very front
of their lab manual.
3. It is helpful to instruct students in the proper operation of the mouse and menu system
as part of the lab introduction.
4. When considering an upgrade for computer systems, memory (RAM) offers the largest
performance increase for the least cost.
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5. Having students work in pairs results in the most successful lab experience. If students
must work in larger groups, have them each get keyboard and mouse experience with
the program.
6. Occasionally, data in the Cell Transport Mechanisms and Permeability module will
appear with “#” symbols next to numbers. In the Simple Diffusion, Facilitated
Diffusion, and Osmosis experiments, the “#” symbol after “rate” data indicates that
equilibrium was not reached for that solute. In the Active Transport experiment, the
symbol after “rate” data indicates 1) for glucose data, that equilibrium was not reached
for glucose; 2) for NaCl and KCl, that transport was interrupted for that solute. In the
Osmosis experiment, the symbol after “pressure” data means that osmotic equilibrium
was not reached.
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.
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PhysioEx™ Exercise 1
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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 pressure.
The 100 MWCO membrane does not allow glucose to pass and therefore glucose will
generate an osmotic influence. Because albumin concentration in the left beaker is 9.00
mM and glucose concentration in the right beaker is 10.00 mM (1.00 mM higher than
the left), the small gradient dictates that an osmotic pressure increase will appear in the
right beaker.
Activity 4: Simulating Filtration (pp. 7–9)
9. Smaller MWCO numbers translate to smaller pore sizes, which correlate with lower filtration rate.
Powdered charcoal did not appear in the filtrate using any membrane.
Increasing the force driving filtration increases filtration rate.
Increasing the pressure gradient effectively increases the filtration rate.
By examining the filtration results, we can predict that the molecular weight of glucose
must be greater than NaCl but less than powdered charcoal.
Activity 5: Simulating Active Transport (pp. 10–11)
7. Solute transport stops before the completion of transport because of a lack of ATP.
Sodium and potassium transport will not occur if ATP is not available.
8. Yes, transport has changed because more ATP is available. This fact supports the earlier
supposition that ATP is required for active transport.
The rate of active transport will decrease if fewer solute pumps are available, but will
still go to completion given enough ATP and time.
You can show that this is an active process by making the sodium concentration in the
right beaker greater than the sodium concentration in the left beaker. Transport will
occur against the concentration gradient in active transport but not in diffusion.
9. Sodium transport is not affected by putting NaCl into the right beaker.
Increasing the number of pump proteins will increase solute transport.
Glucose presence does not affect active transport.
PhysioEx™ Exercise 1
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R E V I E W
S H E E T
version 8
EXERCISE
NAME ____________________________________
LAB TIME/DATE _______________________
1
Cell Transport Mechanisms
and Permeability
Simple Diffusion
1. The following refer to Activity 1: Simulating Dialysis (Simple Diffusion).
Which solute(s) were able to pass through the 20 MWCO membrane?
None
Albumin
According to your results, which solute had the highest molecular weight? ______________________________________
NaCl
Which solute displayed the highest rate of diffusion through the 200 MWCO membrane? __________________________
Using the data from Chart 1, explain the relationship between the rate of diffusion and the size of the solute.
The smaller the solute particle the greater the rate of diffusion.
Facilitated Diffusion
2. The following refer to Activity 2: Simulating Facilitated Diffusion.
Did any of the substances travel against their concentration gradient? Explain why or why not.
No; in facilitated diffusion, a passive process, substances can move only down their concentration gradient.
0.0038
Using your results from Chart 2, what was the fastest rate of facilitated diffusion recorded? _______________.
Describe
8mM glucose with 900 glucose carriers in the membrane
the conditions that were used to achieve this rate. ___________________________________________________________
Increase amount of glucose in solution; increase number of glucose
Name two ways to increase the rate of glucose transport. _____________________________________________________
carriers in the membrane
No
Did NaCl affect glucose transport? ______________________________________________________________________
No; because of its small size, NaCl is able to diffuse down
Did NaCl require a transport protein for diffusion? Why or why not? ____________________________________________
its concentration gradient without the aid of carriers.
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Osmotic Pressure
3. The following refer to Activity 3: Simulating Osmotic Pressure.
For NaCl, which MWCO membrane(s) provided for the net movement of water without movement of NaCl?
20 MWCO
Buildup of osmotic pressure due to the
Explain how you determined this. (Hint: Correlate your results to the data in Chart 3.) ______________________________
presence of non-diffusable NaCl in the solution causes water to diffuse down its concentration gradient.
For glucose, which MWCO membrane(s) provided for the net movement of glucose without net movement of water?
200 MWCO
There was no buildup of osmotic pressure, which indicates that glucose is able to diffuse down
Explain how you determined this. _______________________________________________________________________
its concentration gradient.
No
Is osmotic pressure generated if solutes diffuse freely? _______________________________________________________
The higher the solute concentration, the higher the osmotic
Explain how the solute concentration affects osmotic pressure. ________________________________________________
pressure.
Filtration
4. The following refer to Activity 4: Simulating Filtration.
200 MWCO
Using your results in Chart 4, which MWCO membrane had the greatest filtration rate? ____________________________
The larger the pore size, the greater the filtration rate.
Explain the relationship between pore size and filtration rate. _________________________________________________
Powdered charcoal
Which solute did not appear in the filtrate using any of the membranes? _________________________________________
The filtration rate
What is your prediction of the molecular weight of glucose compared to the other solutes in the solution? _______________
of glucose is less than that of NaCl and urea, so its molecular weight would be greater.
The filtration rate increases.
What happened when you increased the driving pressure? ____________________________________________________
Explain why fluid flows from the capillaries of the kidneys into the kidney tubules.
Pressure is higher in capillaries than in kidney tubules so particles that are small enough are filtered from capillaries into kidney
tubules.
The rate of filtration would decrease.
How do you think a decrease in blood pressure would affect filtration in the kidneys? ______________________________
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Review Sheet 1
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5. The following refer to Activity 5: Simulating Active Transport.
With 1 mM ATP added to the cell interior (left beaker) and the extracellular space (right beaker), was all of the Na moved
No; ATP was depleted at 3 minutes.
into the extracellular space? Why or why not? _____________________________________________________________
The rate of active transport decreases.
Describe the effect of decreasing the number of sodium-potassium pumps. _______________________________________
Sodium moved from the left
Describe how you were able to show that the movement of sodium was due to active transport. ______________________
beaker into the right beaker against its concentration gradient; there was no movement of sodium when there were no Na/K pumps
added to the membrane.
Review Sheet 1
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E X E R C I S E
version 8
2
Skeletal Muscle Physiology
Time Allotment: 2–2.5 hours minimum if students are well-prepared, 3 hours preferred.
Your computer should meet the following minimum requirements for PhysioEx 8.0:
WINDOWS
OS: Windows XP, Vista
Resolution: 1024 × 768
Latest version of Adobe Flash Player
Latest version of Adobe Reader
Browsers: Internet Explorer 6.0 (XP only);
Internet Explorer 7.0; Firefox 2.0
Internet Connection: 56K modem minimum for
website
Printer
MACINTOSH
OS: 10.3.x, 10.4.x
Resolution: 1024 × 768
Latest version of Adobe Flash Player
Latest version of Adobe Reader
Browsers: Safari 1.3 (10.3.x only); Safari 2.0
(10.4.x only); Firefox 2.0
Internet Connection: 56K modem minimum for
website
Printer
Advance Preparation, Comments, and Pitfalls
1. If you are using PhysioEx in a computer lab: Because PhysioEx requires a browser
(such as Firefox or Internet Explorer) and the Flash Player to run, it is recommended
that you make sure these items are already installed on student computers before beginning this lab.
2. If you are using the web version of PhysioEx: Have your students go to
http://www.physioex.com and follow the registration instructions found in the very front
of their lab manual.
3. It is helpful to instruct students in the proper operation of the mouse and menu system
as part of the lab introduction.
4. When considering an upgrade for computer systems, memory (RAM) offers the largest
performance increase for the least cost.
5. Having students work in pairs results in the most successful lab experience. If students
must work in larger groups, have them each get keyboard and mouse experience with
the program.
9