Download Osmosis/Plasmolysis Lab - Honors Biology Overview

Osmosis and Concentration of Solutions
COMPLETED PRIOR TO OSMOSIS/PLASMOLYSIS LAB
Fill-in the blanks BELOW:
Osmosis is the diffusion of ____________________from and area of ______________concentration to an
area of _____________ concentration.
MATERIALS – three plastic cups, 3 carrots, salt, spoon, electronic balance, water, graduated cylinder,
clock.
PROCEDURE:
Label three plastic cups:
 Salt water solution – 25 grams
 Salt water solution – 5 grams
 Fresh water solution
Prepare one for each lab BENCH (groups 1 – 6)
1. Weigh out 25 grams of salt (NaCl) and place the 25 grams of NaCl (table salt) and 100mL of tap
water into your small plastic cup labeled SALT WATER SOLUTION – 25 grams. Mix
2. Weigh out 5 grams of salt (NaCl) and place the 5 grams of NaCl (table salt) and 100mL of tap water
into your small plastic cup labeled SALT WATER SOLUTION – 5 grams. Mix
3. Prepare a second solution with 100mL of tap water into your plastic cup labeled FRESH WATER.
4. Weigh one carrot (grams), record the mass (grams) on the data chart below – FRESH WATER,
THEN place the weighed carrot into the FRESH WATER
5. Weigh your other carrot (grams). Record the mass (grams) on the data chart below – SALT
WATER – 25 grams, THEN place the weighed carrot into the SALT WATER- 25 grams.
6. Weigh your other carrot (grams). Record the mass (grams) on the data chart below – SALT
WATER – 5 grams, THEN place the weighed carrot into the SALT WATER- 5 grams.
7. Record the start time. Allow the carrots to sit in the solutions for 30 minutes.
8. After 30 minutes, take the carrots out of the solution, pat them dry with a paper towel, weigh each
carrot, and record the mass (grams) on the chart below.
START TIME:___________________________ STOP TIME:________________________
Type of solution
Fresh water
Salt water
(25 grams salt)
Salt water
(5 grams salt)
Weight/mass before
soaking (grams)
Weight/mass after
soaking
(grams)
BASED ON YOUR RESULTS – INDICATE
HYPERTONIC, HYPOTONIC, OR
ISOTONIC SOLUTION
OSMOSIS/PLASMOLYSIS LAB
LAB MUST BE COMPLETED IN YOUR COMPOSITION BOOK
Plasmolysis: Shrinkage or contraction of the cell membrane away from the wall of a living plant or bacterial
cell, caused by loss of water through osmosis. It results in wilting of the stems and leaves. If too severe, it can
be fatal to the cell.
REMINDER: THE CELL MEMEBRANE IS ALSO CALLED THE PLASMA MEMBRANE
Define the following terms in your composition book.

Diffusion

Osmosis

Hypertonic solution

Hypotonic solution

Isotonic solution

Solutes

Solvent

Selectively permeable membrane (AP BIOLOGY BOOK OR RESEARCH)

Cytosol (AP Biology book or research)
Purpose/Problem: How do solutions of various salt concentrations influence osmosis in relation to an onion
cell?
Hypothesis?
Materials: (per student group of 3):
Red onion epidermis
Distilled water (in bottle)
Microscope
Plastic cup to make the NaCl solution
Prepared slides (plant, animal, bacterial)
Forceps,
NaCl (table salt)
glass slide
Microscope
Iodine
3mLpipette
paper towels
cover slip
letter ‘e’
PART I
PRACTICE USING THE MICROSCOPE:

Familiarize yourself with the parts of the microscope. Take a look at the picture that you
previously completed in class.
REMINDERS:

ALWAYS focus the object in SCANNING FIRST (red ring). You will use the COARSE focus
knob (LARGE knob).

Once the object is focused, move to low power and focus using the FINE FOCUS KNOB ONLY
(small knob). DO NOT USE THE COARSE FOCUS KNOB.
PROCEDURE: PART 1 – 4 DRAWINGS
1. LETTER ‘e’ – YOU MUST FOCUS IN SCANNING, THEN LOW POWER;
SHOW MRS. COX WHEN YOU HAVE LETTER ‘e’ FOCUSED IN LOW POWER – THEN DRAW IN
LOW POWER.
You must get a signature by your teacher when your drawing is complete.
OBSERVE, DRAW, AND LABEL (USE THE BOOK) THE FOLLOWING THREE SLIDES. DRAW THEM
IN SEPARATE CIRCLES (FIELD OF VIEW).
2. PLANT cell prepared slide (eukaryote) – DRAW IN HIGH POWER
3. ANIMAL cell prepared slide (eukaryote) – DRAW IN HIGH POWER
4. BACTERIAL cell prepared slide (prokaryote) – DRAW IN HIGH POWER
PART II – 3 DRAWINGS - HIGH POWER
ALL DRAWINGS MUST BE COMPLETED IN YOUR COMPOSITION BOOK INSIDE A CIRCLE TO
REPRESENT THE FIELD OF VIEW.
1. Take a small piece of onion skin and place one drop of iodine on the onion skin to stain the skin.
Prepare a wet mount slide of dyed onion skin by placing the dyed onion skin on a glass microscope
slide, place one drop of water on top of the onion skin, place a cover slip over the onion skin. Dry off
any excess water by placing a tissue on one side of the cover slide and drawing up excess water.
Starting on low power, observe under a light microscope.
When you have a clear view of several cells, switch to high power. Make a labeled drawing (cell wall,
membrane, cytosol) of your cells in HIGH POWER. Describe the appearance of the cell after water is
added to the onion skin.

This will give you a record of the original appearance of the onion cells.
2. Prepare a salt solution (NaCl) using one 10 grams of salt and 20 mL of water; stir. Focus the
microscope. While observing the onion cells under the microscope, add a few drops of the salt
solution (NaCl). Take a dropper and add several drops of salt solution to one side of your cover slip
while placing a small piece of paper towel along the opposite edge of the cover slip. The paper should
draw out the water and draw in the salt solution. Observe how the Cells are affected and sketch your
results in high power. Draw, color, and label a picture in your composition book. REMEMBER to title
the drawing. Describe the appearance of the onion cells after the NaCl was added.
3. Replace the sodium chloride (NaCl) solution with distilled water in the same way that the salt solution was
added. Make a properly labeled drawing of the cells' appearance in the circle to the right. Describe the
appearance of the cell after adding water.
DISCUSSION QUESTIONS:
Complete the following questions in your COMPOSITION notebook; USE COMPLETE SENTENCES.
Make sure you correctly use ALL of the following terms at least once in your explanations. Hypertonic
solution, hypotonic solution, isotonic solution, solute, solvent, selectively permeable membrane,
diffusion, osmosis, and plasmolysis.
1. In the winter, grass often dies near roads that have been salted to remove ice. What causes this to
happen?
2. Why do grocery store owners spray fresh fruits and vegetables with water?
3. Roads are sometimes salted to melt ice. What does this do to plants around the roadside and why?
4. If a shipwrecked crew drinks seawater, they will probably die. Why?
5. If a bowl of fresh strawberries is sprinkled with sugar, a few minutes later the berries will be covered
with juice. Why?
6. How does the cells selectively permeable membrane protect it from cell death?
7. Draw a diagram of a cell floating in a hypertonic solution and a cell floating in a hypotonic solution.
Which solution would be best for the cell? Use dots to represent salt in the water. Label your drawings (salt,
water, hypertonic, hypotonic).
CONCLUSION:
PLEASE FOLLOW THE LAB PROTOCOL GIVEN (HANDOUT IN THE BACK OF YOUR COMPOSITION
BOOK) TO COMPLETE YOUR CONCLUSION.
EXTENSION ACTIVITY: If you complete the lab requirements prior to the deadline, you may prepare,
observe, and draw a wet-mount slide using pond water. Total points = 1% grade increase. ALL other
work must be complete, detailed, accurate, and of excellent quality. Please show me your work and I
will provide the pond water and materials.
ALL DONE!!