ART111 Lecture Notes - Lecture 3: Dialysis Tubing, Membrane Transport, Print Screen
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Cell Membranes Lab Report
- Diffusion
- Compare the following terms: solvent, solute, andsolution.
- Go to Lab, Section I, Exercise 1 to explore the factorsinfluencing the rate of diffusion and complete the following:
- Predict how molecular mass and temperature may affect theoutcome of this experiment.
- Record the data from information in the Lab in the tablebelow.
| Time (min) | Diameter (mm) | |||
5°C MB | 5°C PP | 23°CMB | 23°C PP | |
0 | ||||
15 | ||||
30 | ||||
45 | ||||
- Construct a line graph of the data from the table above. Yourgraph should include labeled axes, units, and a legend indicatingwhich treatment is presented. Sign, date and prepare an image ofyour graph and include it with this lab report.
- Osmosis
- Go to Lab, Section II, Exercise 2 to view a demonstration ofosmosis and answer the following questions:
- Describe the net movement of water in osmometer 1.
- How is the movement of water molecules related to theconcentration gradient of the solution?
- Go to Lab, Section II, Exercise 3 to observe the effect ofsolute concentration on the rate of osmosis. Answer the followingquestions:
- Was the net movement of water in bags 1 to 4 into or out of thebags?
- Explain the results from bags 4 and 5.
- Selective Permeability of Membranes
- Go to Lab, Section III, Exercise 4 to learn about theimportance of selectively permeable membranes, then complete thetable and answer the following questions:
Contents of Beaker | ||
0 Min | 30 Min | |
Starch | ||
Chloride ion | ||
- Which substances diffused through the dialysis membrane?
- How does dialysis tubing model the selective permeability of aplasma membrane?
- Tonicity
- Go to Lab, Section IV, Exercise 5 and 6 to observe plasmolysisin Elodea cells and tonicity in red blood cells. Summarizethe concept of tonicity using blood and Elodea cells asexamples. Your description should incorporate these terms: turgid,plasmolysis, hemolysis, and crenation.
Cells | Isotonic Solution | Hypertonic Solution | Hypotonic Solution |
Elodea | |||
RBC |
- Based on your previous work, reproduce the table below and drawan illustration of a single cell in each box. Include arrows toshow the direction of water flow relative to each cell and dots tosymbolize solutes. Sign, date and prepare an image of your drawingand include it with this lab report.
Cells | Isotonic Solution | Hypertonic Solution | Hypotonic Solution |
Elodea | |||
RBC |
Summary Questions
- Compare diffusion and osmosis. Give an example of each.
2. In which direction will osmosisoccur if a 15% sugar solution is separated from a 25% sugarsolution by a selectively permeable membrane?
3. Why did osmosis, but not diffusionof sucrose molecules, occur across the dialysis membrane containing20% sucrose solution?
4. You are having a party and thecelery is limp. What might you do to make the celery crisp (turgid)again? What will occur in the cells?
5. A small amount of fertilizer(mineral salts) will stimulate plant growth, but over fertilizationcan kill plants? Why?
6. Michael adds sugar to his coffee.Explain what in this drink is the solvent, solute, and solution.
7. You add a cube of sugar to yourdrink. How could you speed up the diffusion of sugar moleculeswithout stirring?
8. How is dynamic equilibriumestablished within a solution?
1. Which of the following best describes a condition where a membrane separates two solutions that are NOT in equilibrium?
| A | a rainbow |
| B | equilibrium |
| C | a homogeneous solution |
| D | neighboring solutions that have unequal concentrations of molecules |
2. In this lab, we will use dialysis tubing to....
| A | simulate biological membranes |
| B | separate blood from urine |
| C | turn starch blue |
| D | turn starch brown |
3. Biological membranes have different types of pores and channels, and different permeability to small molecules depending on size and charge. In this lab, you can assume that the dialysis tubing we are using are permeable to....
| A | starch |
| B | water and potassium iodide |
| C | complex sugars |
| D | small animals |
4. Kinetic energy is a property of the atom, and also of more complex structures such as molecules. You can actually see kinetic energy of non-living things in action under the microscope. When we visualize this, we call what we see...
| A | diffusion |
| B | Brownian motion |
| C | osmosis |
| D | all of the above |
5. One word to describe the effect of water diffusion across a membrane, which alters the water pressure on one side of the membrane with respect to the other is....
| A | osmosis |
| B | lysis |
| C | aquaporin |
| D | equilibrium |
6. Suppose that you place a red blood cell in a hypertonic solution containing penetrating molecules. In this environment, you would expect the cell to eventually
| A | swell and burst |
| B | shrink |
| C | remain the same in size |
| D | photosynthesize |
7. For the "egg lab", what is the main objective?
| A | to determine which egg has more mass |
| B | to determine which egg is hypertonic to the other |
| C | to determine which solution the egg is placed in is hyper- or hypo-tonic solution |
| D | to determine which egg is isotonic with the egg |
8. The main difference between a 'prediction' and a 'hypothesis', is that predictions....
| A | are framed as an "if...then...because" statement |
| B | are framed as a general statement |
| C | are framed as an "always....true" statement |
| D | are framed as an "correct....incorrect" statement |
9. Read each of the following procedural steps for plasmolyzing Elodea sprig and then select the correct order below.
Locate a region of healthy cells and sketch a few adjacent cells
Sketch the plasmolyzed cell
While touching one corner of the coverslip with a piece of Kimwipe to draw off the
water, add a drop of concentrated salt solution to the opposite corner
Obtain a leaf from an Elodea or Water sprite plant
| A | 4, 2, 3, 1 |
| B | 3, 1, 4, 2 |
| C | 2, 3, 1, 4 |
| D | 4, 1, 3, 2 |
Below, is a completed lab. After completing this lab, I was asked the following question:
What changes would you make, if any, if you did this lab again?
I'm having a hard time thinking of what I would do different. Please help!
Observations & Questions for Part 1
Record your observations and your time and temperature data in tables. Use one table for the pure water and one table for the salt solution.
| Data Table 1: Pure Water and Salt Solution | ||||
| Seconds | Distilled H20 Room temp | Distilled H20 Ice bath | Saltwater Room temp | Saltwater Ice bath |
| 0 | 23 | 23 | 17 | 23 |
| 30 | 23 | 10 | 20 | 7 |
| 60 | 23 | 4 | 22 | 1 |
| 90 | 22.5 | 1 | 22 | 0 |
| 120 | 22.5 | 0 | 22 | 0 |
| 150 | 0 | 22 | -1 | |
| 180 | -1 | 22 | -1 | |
| 210 | -1 | 22 | -2 | |
| 240 | -2 | -2 | ||
| 270 | -1 | -2 | ||
| 300 | -1 | -2 | ||
| 330 | -1 | -2 | ||
| 360 | -1 | |||
| 390 | 0 | |||
| 420 | 0 | |||
| 450 | 0 | |||
| 480 | 0 | |||
| 510 | 0 | |||
| 540 | ||||
| 570 | ||||
| 600 | ||||
| 630 | ||||
| 660 | ||||
Make two graphs of your data. On one graph plot the data from the pure water. On the other graph plot the data from the salt solution. On both plot temperature on the y-axis and time on the x-axis.
A. Record the freezing point of the pure water and the freezing point of the salt solution.
Freezing point of salt Sol: -2 degree Celsius
Freezing point of pure H2O: 0 degree Celsius
B. How do these two freezing points compare?
The freezing point of salt water is lower than the freezing
point of fresh water. Salt in the water lowers the freezing point
of water.
C. What are some practical applications of freezing point depression, boiling point elevation, and vapor pressure lowering?
Some practical applications of freezing point depression
are antifreeze in a radiator and salt on the road used to melt
ice in the winter. Some practical applications of boiling point
elevation are a sealed container and possibly a pressure cooker.
Some practical applications of vapor pressure lowering are freeze
drying and steam engines.
Questions - Part 2
To what biological structure is the dialysis bag comparable? How is it similar? How is it different?
The plasma membrane is comparable to the dialysis bag.
The similarity between them is that they are both semipermeable.
The difference is the dialysis bag acts as a permeable membrane,
however, purely based on its pore size, the small molecules are
able to get through but the bigger molecules are unable to. The
plasma membrane is a more complex system that uses both active
and passive transport to allow the molecule to move through.
In biological systems if a cell is placed into a salt solution in which the salt concentration in the solution is lower than in the cell, the solution is said to be hypotonic. Water will move from the solution into the cell, causing lysis of the cell. In other words, the cell will expand to the point where it bursts. On the other hand, if a cell is placed into a salt solution in which the salt concentration in the solution is higher than in the cell, the solution is said to be hypertonic. In this case, water will move from the cell into the solution, causing cellular death through crenation or cellular shrinkage. In your experiment is the Karo