LAB 9
CELL TRANSPORT
Objective: To identify, demonstrate and explain the various physical processes used within cells
and the body. To define and understand movement of substances into and out of a cell using the
terms isotonic, hypotonic and hypertonic.
I. Diffusion
A. Diffusion of Gases
1.
2.
3.
4.
Open a bottle of perfume or other strong-smelling substance at the front of the room.
Ask fellow classmates to raise their hands, as they smell the substance.
Note the movement of the smell from one area of the room to another.
Write down your observations.
QUESTIONS
1.
Was there a pattern to the movement of the smell? Why or why not?
2.
What caused the movement of the odor? Be specific when explaining.
3.
Define diffusion –
B. Diffusion Within Liquids
1.
2.
3.
4.
Obtain two test tubes and fill each approximately one half full of distilled water.
Carefully add some copper sulfate (CuSO4) to one of the tubes and some potassium permanganate (KMnO 4) to
the other tube.
Let each tube sit for at least 30minutes. Observe any changes throughout the duration.
Observations:
Copper sulfate (CuSO4)
Potassium permanganate (KMnO4)
QUESTIONS
1.
What happened in each of the tubes over the 30-minute period ?
34
2.
Was there a difference in the rate of diffusion in the two tubes? If so, what was the difference?
3.
How do you explain the cause of these results?
4.
Name two places in the body where a solid must diffuse into a liquid.
C. Diffusion Through a Colloid
Substances in the body must often diffuse through a colloid (such as Cytoplasm) in order to reach their destination.
1.
2.
Observe this process by dropping a few crystals of potassium permanganate onto a plate of agar gelatin.
Observe the results for the next 20 minutes.
QUESTIONS
1.
What happened to the crystals on the gelatin?
2.
What is a colloid?
3.
Give two examples of where this process takes place in the body.
II. Osmosis
A. Thistle Tube Osmometer
1.
2.
3.
4.
5.
Set up the osmometer as demonstrated by your instructor. (See diagram)
Bending or handling the membrane too much will cause unwanted leaks.
Mark the level of the molasses when you place it in the beaker of water.
Observe the level of the molasses for the next 30 minutes.
Observations:
QUESTIONS
1.
What happened to the level of the molasses?
2.
Explain what caused the movement of the molasses.
35
3.
Why didn’t the molasses leave the thistle tube and enter the water in the beaker?
4.
If the thistle tube were a cell and the water in the beaker were the solution surrounding the cell:
a.
Is the solution isotonic, hypotonic, or hypertonic? Explain.
b.
Are there more solutes inside or outside the cell?
c.
How long would water move into the cell? What might result from this?
5.
Give some examples of where osmosis is taking place in your body.
6.
Is osmosis diffusion? Explain.
B. Osmosis in Potato Cells
1.
2.
3.
4.
5.
6.
Obtain six plugs of potato.
Three plugs will be soaked in distilled water, the other three will be soaked in 10% NaCl.
Measure the volume of the plugs prior to beginning by putting the set of three plugs in a graduated cylinder of
water.
Measure the water before and after you put the plugs in to determine the volume change caused by the plugs.
Record the results in the table below.
After determining the volume of the plugs, place the set of plugs into their designated solution and let soak for
30 minutes.
After 30 minutes, remove the potato plugs and observe the rigidity of the plugs in each set. Remeasure the
volume of each set of plugs and record the results below.
Water (mL)
Original Volume of Potatoes
Volume After 30 min. in Soln.
Volume Change (+ or -)
Observations
QUESTIONS
1.
Which group of plugs gained volume? Explain.
36
10%NaCl (mL)
2.
Which group of plugs lost volume? Explain
3.
What type of solution was the 10% salt solution? The distilled water?
4.
How did the rigidity of the plugs in the two solutions compare? Why the difference?
5.
In order to maintain the normal osmolarity of a potato cell, in what type of solution would need to put the
potatoes?
C. Osmosis in Human Cells
1.
2.
3.
4.
Prepare three blood slides as directed by your instructor.
Use the following solutions to make the three slides:
a. Add one drop of distilled water when preparing the first slide.
b. Add one drop of 0.9% NaCl solution when preparing slide two
c. Add one drop of 5% NaCl solution when preparing slide three.
Cover each slide with a cover slip and observe under the microscope on high power.
Draw and record your observations below.
Slide 1 [Distilled H2O]
Slide 2 [0.9% NaCl]
QUESTIONS
1.
Which slide contained cells in a hypertonic solution? Hypotonic? Isotonic?
2.
Describe and explain the cause of the appearance of the cells in each slide.
3.
What is a physiological saline solution?
37
Slide 3 [5% NaCl]
4.
Define the following terms:
a.
crenation –
b.
hemolysis –
D. Dialysis
1.
2.
3.
4.
5.
Soak a piece of dialysis tubing in distilled water to soften.
Remove the tubing from the water and tie off one end with string.
Fill the tube with the prepared test solution and tie off the other end.
Place the dialysis tube ‘sausage’ into a beaker of distilled water and let sit for 30 minutes.
After 30 minutes, test the water in the beaker for the following substances to determine if they have left the
tubing and entered the water.
Contents of test solution in dialysis tubing:
a.
Water
Glucose
Albumin (protein)
Starch
NaCl
Test for NaCl
i.
ii.
iii.
iv.
b.
Test for Glucose
i.
ii.
iii.
iv.
c.
Place several mL of water from the beaker in a test tube
Add several drops of silver nitrate solution (AgNO3)
Formation of a white, cloudy precipitate indicates the presence of NaCl
Record results below
Place several mL of water from the beaker in a test tube.
Add an equal amount of Benedicts solution to the tube.
Warm the tube in a hot water bath for 5 to 10 minutes.
Look for a color change. Any change to green, yellow, orange or red indicates the presence of glucose
Test for Starch
i. Place several mL of water from the beaker in a test tube.
ii. Add several drops of iodine solution.
iii. A bluish or purplish-black color indicates the presence of starch.
d.
Test for Albumin (protein)
i. Place several mL of water from the beaker in a test tube.
ii. Carefully add several drops of nitric acid (HNO3) to the tube. [NITRIC ACID IS CORROSIVE]
iii. Formation of a white, cloudy precipitate indicates the presence of protein.
Test for Presence of:
Substance Added
NaCl
Silver nitrate
Observations Following Test
Glucose
Starch
Albumin
38
Substance Present?
( + or -)
QUESTIONS
1.
Define dialysis:
2.
Which of the four substances left the dialysis tube and entered the water?
3.
Why did some substances get through the membrane while others didn’t?
4.
What physical characteristic of albumin affected its ability to pass through the membrane?
5.
When solutes move, what usually follows?
III. Filtration
A. Filtration of An Unknown Solution
Filter an unknown solution to determine what will pass through the filtration membrane.
1.
2.
3.
4.
Place a piece of folded filter paper in a funnel.
Put the funnel in a test tube.
Fill the funnel with the test solution.
Continue adding fluid to the filter until four test tubes are filled at least one inch high with the filtrate.
Fold and
crease lightly
in half
Then, fold in
half again
Filtration apparatus
39
Open out like
a cone
5.
Use one tube of filtrate to test for each of the following substances.
a.
Test for Salt
i.
b.
Test for Starch
ii.
c.
See section ‘5a’ on the previous page (dialysis experiment) for the procedure to test for NaCl. Record
the results below.
See section’5c’ on the previous page for the procedure to test for starch. Record the results below.
Test for Charcoal
i. Observe the filtrate in the test tube. Any gray or black particles indicate presence of charcoal.
ii. Indicate that the charcoal passed through the filter.
iii. Record the results below.
d.
Test for Copper Sulfate (CuSO4)
i. Observe the filtrate in the test tube for a bluish or aqua color.
ii. A blue color indicates copper sulfate has passed through the filter.
iii. Record the results below.
Substance Present?
( + or -)
Test
NaCl
Starch
Charcoal
Copper sulfate
QUESTIONS
1.
Name three things that will determine whether a substance will pass through a filtration membrane.
2.
In a closed system, what force is necessary for filtration to take place?
3.
How could you increase this force?
4.
Where does filtration take place in the body?
40