lap homework
salma 0133
OsmosisandDialysisFa16.pps.ppt
2) OSMOSIS AND DIALYSIS
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Click Here To Start Experiment #2
Sucrose
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To magnify the blackboard click on it to view a discussion on membrane transport
There are two parts to this experiment # 2. PART 1 will consider OSMOSIS and PART 2 will consider DIALYSIS. You will need to supply the following in your lab report for experiment # 2
Part 1 (Osmosis)
Table of Osmotic Potential and Time
Graph of Osmotic Potential vs Time
Graph of Osmotic Change vs Time (Osmotic Rate)
Answers to Questions (1 - 7)
Part 2 (Dialysis)
Table of Dialysis Tests
Answers to Questions (1 - 6)
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OSMOSIS is the diffusion of water through a selectively permeable membrane. Water will generally move quite freely through the cell membrane by diffusion. Osmotic movement of water occurs when the solute (non-penetrating) concentrations differ between the opposing sides of the cell membrane. A difference in solute (non-penetrating) concentrations means there is a difference in water concentrations and water will move from the region of higher concentration to a region of lower concentration.
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For example, water osmotically moves into a cell when the fluid outside the cell has more water (less solutes) than the fluid inside the cell. In this case, as water moves into the cell, it swells as the water pressure inside the cell increases.
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Red Blood Cell
Distilled Water
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DIALYSIS is the separation of solutes according to their size by diffusion through a permeable membrane. Depending upon the molecular pore size of the membrane, solutes will either diffuse across the membrane or be restricted by their size.
The device you will be using to collect data for the experiments is an osmometer. This is a device used to measure osmotic force.
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PART 1 (OSMOSIS)
MATERIALS
Thistle tube (with mm markings)
Thistle tube stand
Dialysis tubing (selectively permeable membrane)
Rubber band
Sugar solution (20 % sucrose)
Beaker
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H2O
Sucrose
H2O
Sucrose
You will need to record your data from this experiment on your Data Table of Osmotic Potential and Time.
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Procedure
Click on the thistle tube stand in order to bring it to the table
You will know you are pointing to the stand when the cursor changes.
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H2O
Sucrose
H2O
Sucrose
STAND
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Now click on the thistle tube funnel to attach it to the tube stand.
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H2O
Sucrose
H2O
Sucrose
Thistle tube
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Next we will put the dialysis tubing on the bulb end of the thistle tube. You will need only a small piece. Click on the dialysis tubing on the shelf.
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H2O
Sucrose
H2O
Sucrose
Tubing
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Put a rubber band on the tube and dialysis tubing to hold it in place. You can accomplish this by clicking on the rubber bands on the shelf.
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H2O
Sucrose
H2O
Sucrose
Rubber Band
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Put the bulb of the thistle tube into the beaker of water. The water is distilled which means that it has no solutes in it (100 % water). Click on the beaker labeled as H2O.
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H2O
Sucrose
Sucrose
H2O
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Now we will pour the sucrose solution into the thistle tube from the top. The sucrose solution is a 20 % sugar solution (80 % water). Click on the beaker labeled as Sucrose.
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Sucrose
Sucrose
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Record the original millimeter measurement of the sucrose solution in the column of the thistle tube on your data sheet. Next, record the movement of the sucrose solution every 15 minutes for 90 minutes. Click on the start button of the clock to begin measuring.
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START
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05:00
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20:00
25:00
30:00
35:00
40:00
45:00
50:00
55:00
60:00
65:00
70:00
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80:00
85:00
90:00
3
10
16
22
26
30
33
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From the data you have collected you will need to produce two graphs. One of the graphs will plot Osmotic Potential vs Time. The other graph will plot Osmotic Change vs Time.
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Answer the questions that follow your graphs about the experiment you have performed.
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You are now ready to begin part two of experiment #2.
In this part we will be concerned about a process related to osmosis called Dialysis.
Glucose
Glucose
Starch
Starch
Lugol’s
Lugol’s
H2O
H2O
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Dialysis is the diffusion of a solute (salt, glucose, etc.) across a selectively permeable membrane. In this case the solute molecules always move from the stronger concentration (hypertonic) to the weaker (hypotonic).
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Dialysis involves the movement of some, but not all, of the dissolved substances in a solution. The substance that moves has small molecules, so these can pass through the pores in the membrane, but other substances, with larger molecules, cannot escape.
The green molecules are small enough to fit through the pores of the semi permeable membrane while the red molecules are too large.
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This process occurs normally in the kidney. Substances with small molecules, such as salts, glucose and urea, continuously pass out of the blood through a membrane under pressure, but useful substances are later reabsorbed. Waste substances are then excreted as urine.
Kidney
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In this exercise you will measure diffusion of small molecules through dialysis tubing, an example of a semi permeable membrane. The movement of a solute through a semi permeable membrane is called dialysis. The size of the minute pores in the dialysis tubing determines which substance can pass through the membrane.
The light blue object here represents a section of dialysis tubing. The red spheres represent molecules which are able to move through the dialysis membrane, while the blue spheres represent molecules too large to move out of the dialysis membrane solution.
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A solution of glucose and starch will be placed inside a bag of dialysis tubing. Distilled water will be placed in a beaker, outside the dialysis bag. The dialysis bag with the starch glucose solution will be inserted into the beaker of distilled water. After 30 minutes have passed, the solution inside the dialysis tubing and the solution in the beaker will be tested for glucose and starch. The presence of glucose will be tested with glucose test strips. The presence of starch will be tested with Lugol's solution (iodine potassium iodide).
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PART 2 (DIALYSIS)
MATERIALS
30 cm section of dialysis tubing
String
15 % glucose solution
1 % starch solution
Glucose test strips
Lugol’s solution
Distilled water
2 Test tubes
Large beaker
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Procedure
Obtain a 30 cm piece of dialysis tubing
Click on the tubing to obtain the dialysis tubing
Glucose
Glucose
Starch
Starch
H2O
H2O
Lugol’s
Lugol’s
Tubing
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We will now tie one end of the dialysis tubing with the string.
Click on the string to tie the tubing
Glucose
Glucose
Starch
Starch
H2O
H2O
Lugol’s
Lugol’s
String
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We can now place the dialysis tubing in distilled water to moisten it so that it will be easier to open.
Click on the beaker of distilled water to bring it to the table then click on the dialysis tubing to place the tubing in the water.
Glucose
Glucose
Starch
Starch
H2O
Lugol’s
Lugol’s
H2O
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While we let the dialysis tubing soak, we can access the glucose and starch solutions.
Bring the two solutions to the table by clicking on either of them.
Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Glucose
Glucose
Starch
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We will need to develop a method to test for glucose in a solution as well as test a solution for starch.
Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Glucose
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You will need to record your data from this experiment on your Data Table of Dialysis Test.
Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Glucose
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Glucose
We will be using glucose test strips to test a solution for the presence of glucose.
When the strip is exposed to glucose it will change color from yellow to blue.
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Water
We will be using Lugol’s solution to test for the presence of starch.
When Lugol’s solution is in the presence of starch the solution will change to a dark blue color.
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Glucose
Click on the test strips to bring them to the table.
Next we will test the Glucose solution and the distilled water where the dialysis tubing is now soaking for the presence of glucose.
Test Strips
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Click on one of the glucose test strips.
You will be testing the glucose solution for the presence of glucose.
As you have predicted, you will get a positive test. Record your data.
Glucose
The color change on the strip shows a positive test for the presence of glucose
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Click on another test strip to test the distilled water for the presence of glucose.
Remember a positive test will turn the yellow end of the strip to blue.
Record your results in your data table.
Glucose
Record your data
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Next we will test for starch in the starch solution and the distilled water.
You will be using Lugol’s solution to test for starch.
If starch is present the solution will turn a dark blue color.
Glucose
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Glucose
Starch
H2O
Lugol’s
Lugol’s
Starch
Click on the blue bottle of Lugol’s solution on the shelf to bring it to the table.
You will need a test tube to test a small portion of the starch solution.
Next click on the test tube rack.
Glucose
Test tube
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Glucose
Starch
H2O
Lugol’s
Click on one of the eyedroppers on the shelf to add starch to the test tube.
Glucose
Starch
Next click on the eyedropper in the bottle of Lugol’s solution to add a few drops to the starch solution in the test tube.
Record your results on your data sheet.
Eye Dropper
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Glucose
Starch
H2O
Lugol’s
Next we will test the distilled water for the presence of starch.
Click on the test tube rack to get a clean test tube
Glucose
Starch
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Glucose
Starch
H2O
Lugol’s
Click on a fresh eyedropper from the shelf to add distilled water to the test tube.
Glucose
Starch
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Glucose
Starch
H2O
Lugol’s
Next click on the eyedropper in the Lugol’s solution to add a few drops to test for starch.
Record your results.
Glucose
Starch
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Glucose
Starch
H2O
Lugol’s
Next we will open the dialysis tubing and fill it with about ½ full of starch solution and about ½ full of glucose solution.
Leave enough of the tubing so that you can tie the end shut.
Glucose
Starch
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Glucose
Starch
H2O
Lugol’s
Click on the dialysis tubing in the distilled water beaker to remove it so that it can be opened.
Next click on the starch or glucose solution to fill the dialysis tubing.
Starch
Glucose
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Glucose
Starch
H2O
Lugol’s
Next click on the yellow string to tie the top of the dialysis bag.
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Glucose
Starch
H2O
Lugol’s
Now click on the dialysis bag to insert it into the distilled water.
Leave the dialysis bag in the distilled water for 30 minutes.
Click the start button on the timer.
START
00:00
05:00
10:00
15:00
20:00
25:00
30:00
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Glucose
Starch
H2O
Lugol’s
Remove the dialysis bag by clicking on it.
Open one end of the dialysis tubing by clicking on the yellow string holding one end together
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Glucose
Starch
H2O
Lugol’s
Click on the test tube rack to obtain a test tube.
We will add a small amount of solution from the dialysis tubing to the test tube to test for glucose and starch.
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Glucose
Starch
H2O
Lugol’s
Click on one of the blue eyedroppers on the shelf to add solution from the dialysis tubing.
Next click on the one of the glucose test tapes to test for glucose.
Record your results
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Glucose
Starch
H2O
Lugol’s
Now we can test for starch by using a few drops of Lugol’s solution.
Click on the eyedropper in the Lugol’s solution to add to the dialysis tube solution.
Record your results.
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Glucose
Starch
H2O
Lugol’s
We will now perform the same tests for glucose and starch on the solution of distilled water in which the dialysis tubing soaked for 30 minutes.
We will need a clean test tube. Click on the test tube rack.
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Glucose
Starch
H2O
Lugol’s
Click on one of the blue eyedroppers on the shelf to add solution from the distilled water.
Next click on the one of the glucose test tapes to test for glucose.
Record your results
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Glucose
Starch
H2O
Lugol’s
Now we can test for starch by using a few drops of Lugol’s solution.
Click on the eyedropper in the Lugol’s solution to add to the distilled water.
Record your results.
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You are finished with part 2 of experiment # 2, be sure that you answer the questions pertaining to this part of the experiment.
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At this point you have finished experiment # 2, Parts 1 and 2 for
this lab.
End this Session
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