PEX 01 03

Name: Yvette
Exercise 1: Cell Transport Mechanisms and Permeability: Activity 3: Simulating Osmotic Pressure Lab Report
Pre-lab Quiz Results
You scored 50% by answering 2 out of 4 questions correctly.
1. Which of the following is true of osmosis?
Your answer : b. Movement is against the concentration gradient of water.
Correct answer: c. It is a type of diffusion.
2. Which of the following occurs when a hypertonic solution is added to cells?
You correctly answered: d. The cells shrink.
3. The variable that affects osmotic pressure is
Your answer : b. the concentration of diffusing solutes.
Correct answer: a. the concentration of nondiffusing solutes.
4. The net movement of water would be into the cell in a
You correctly answered: b. hypotonic solution.

02/04/15

page 1

Experiment Results
Predict Question:
Predict Question 1: What effect do you think increasing the Na+ Cl- concentration will have?
Your answer : a. increased osmotic pressure
Predict Question 2: What do you think will be the pressure result of the current experimental conditions?
Your answer : b. pressure above the right beaker
Stop & Think Questions:
Why do you think there is no pressure change?
You correctly answered: b. Sodium is able to diffuse through the pores.
Why do you think there was no pressure change?
You correctly answered: c. There is no net movement of water because the solute concentrations are the same.
Experiment Data:
Run Number
1
1
1
2
2
2
3
3
3
4
4
4
5
5
5
6
6
6
7
7
7

Solute
Na+ ClAlbumin
Glucose
Na+ ClAlbumin
Glucose
Na+ ClAlbumin
Glucose
Na+ ClAlbumin
Glucose
Na+ ClAlbumin
Glucose
Na+ ClAlbumin
Glucose
Na+ ClAlbumin
Glucose

MWCO
20
20
20
20
20
20
50
50
50
100
100
100
100
100
100
200
200
200
200
200
200

Start Conc. L
5.00
0.00
0.00
10.00
0.00
0.00
10.00
0.00
0.00
0.00
0.00
8.00
0.00
0.00
8.00
0.00
0.00
8.00
0.00
9.00
0.00

02/04/15

Pres. L
170
170
170
340
340
340
0
0
0
136
136
136
0
0
0
0
0
0
153
153
153

page 2

Start Conc. R
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
8.00
0.00
0.00
0.00
0.00
0.00
10.00

Pres. R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

Rate
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0167
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0036
0.0000
0.0000
0.0044

Post-lab Quiz Results
You scored 50% by answering 2 out of 4 questions correctly.
1. If you double the concentration of a nondiffusible solute that is on one side of a membrane, the osmotic pressure will
You correctly answered: c. double.
2. Which membrane did not allow Na+ Cl- to pass through?
You correctly answered: a. 20 MWCO
3. When a solute is able to diffuse through a membrane
Your answer: c. there is net movement of water.
Correct answer: b. equilibrium is reached.
4. Water diffuses
Your answer: a. against its concentration gradient.
Correct answer: c. toward solutes.

02/04/15

page 3

Review Sheet Results
1. Explain the effect that increasing the Na+ Cl- concentration had on osmotic pressure and why it has this effect. How well did the results compare with your prediction?
Your answer:
I was right, increasing the concentration doubled the pressure. This is because there was more net movement as the diffusion process occured.
2. Describe one way in which osmosis is similar to simple diffusion and one way in which it is different.
Your answer:
They both transport in the same way down the concentration gradient. They differ though through the fact that simple diffusion doesn't need a carrier.
3. Solutes are sometimes measured in milliosmoles. Explain the statement, “Water chases milliosmoles.”
Your answer:
Osmosis is the diffusion of whatever the solvent is and in most cases it is water. The water is going to want to go where the higest concentration of of solute therefore it will "chase" it.
4. The conditions were 9 mM albumin in the left beaker and 10 mM glucose in the right beaker with the 200 MWCO membrane in place. Explain the results. How well did the results compare with your prediction?
Your answer:
I was wrong in my conclusion and the pressure increased on the left beaker side with the Albumin.

02/04/15

page 4