Name________________________ Date________ Block____
LAB: Observing Osmosis in Plants
Background Information:
When one area has more of a substance than another, that area has a high concentration of substance.
When an area has less of a substance than another, it has a low concentration of the substance. In diffusion,
substances in an area of higher concentration move to an area of lower concentration. This occurs until the
amount of substances on each side of the membrane is equal. This equal distribution of substances is called
equilibrium.
Diffusion is a form of passive transport. It does not require cells to use energy to move materials.
Active transport requires a cell to use energy to move materials.
Osmosis is another form of passive transport. Osmosis is the movement of water molecules from an
area of higher concentration to an area of lower concentration.
Plant and animal cells react differently to osmosis. When a plant cell undergoes osmosis and water
enters the cell, the cell is said to have turgor pressure - the cytoplasm swells with water, but the cell wall
keeps the cell from bursting (lysing). When a plant cell undergoes osmosis and water leaves the cell, the cell is
said to plasmolyze (shrink/shrivel) - the cytoplasm shrivels from a lack of water and the cell will eventually die.
When an animal cell, which does not have a cell wall, undergoes osmosis and water enters the cell, the cell will
eventually burst (lyse). When an animal cell undergoes osmosis and water leaves the cell, the cell shrivels and
eventually dies from lack of water.
Objectives:
1. Observe living plant cells as they respond to environmental changes
2. Make accurate microscope drawings of plant cells undergoing plasmolysis and turgor pressure.
3. Determine movement of water within cells based on observations.
Materials:
- microscope
- slide
- cover slip
- forceps
- eggs
- dropper
- distilled H2O
- 10% salt H2O
- paper towel
-vinegar
- carrots
- corn syrup
- green colored pencil
- Elodea
Pre-Lab: Fill out the chart below using your notes and the background information on the front page of this
lab.
Definition (with examples)
Diffusion
Equilibrium
Passive
Transport
Active
Transport
Osmosis
Turgor
Pressure
Plasmolyze
Picture
Procedures and Observations
Part A: Microscopic Observations - Read all instructions before you begin work on this lab.
1. Wet mounts of elodea leaves have been prepared for you. You will be observing an elodea leaf that is
in three different solutions: spring water, salt water, and distilled water. Pay special attention to the
cell membrane and the position of the chloroplasts.
2. Look at the elodea leaf that is in the spring water (90% water). Draw four cells as they appear under
high power. Label the cell wall, chloroplasts, and cytoplasm.
Elodea in spring water
_______ x
3. Observe the elodea leaf that is in the salt water (80% water). Draw four cells as they appear on high
power, and label the cell wall, chloroplasts, and cytoplasm.
Elodea in salt water
______ x
4. Observe the elodea leaf that is in the distilled water (100% water). Draw four cells as they appear on
high power, and label the cell wall, chloroplasts, and cytoplasm.
Elodea in distilled water
_____ x
Part B: Macroscopic Observations
1. Feel the carrots that have been soaking in fresh water and salt water. Write down what type of solution
you think the carrot is in for each solution. Write down your observations about the condition of the
carrots in the chart below. Then return the carrot to the jar.
Solution
Type of solution
(Isotonic, hypotonic, or
hypertonic)
Observations
Carrot in Distilled Water
Carrot in Salt Water
2. Observe the eggs that have been soaking in distilled water, vinegar, and corn syrup. Write down what type
of solution you think the egg is in for each solution. Write down your observations about the condition of
the eggs in the chart below.
Solution
Egg in corn syrup
Egg in vinegar
Egg in distilled water
Type of solution
(Isotonic, hypotonic or
hypertonic)
Observations
Analysis- Part A: Microscopic Observations (Elodea)
1. Of the three solutions you observed (spring water, salt walter, distilled water) what solution was an
isotonic solution? A hypotonic solution? A hypertonic solution?
2. When placed in a hypertonic solution, what type of molecules left the plant cells? Explain why they left
and what observations you made that confirmed this.
3. Could Elodea live in a salt water environment? EXPLAIN your answer!
4. When placed in a hypotonic solution, what type of molecules entered the plant cells? Explain why they
entered and what observations you made that confirmed this.
5. What would have happened if the cells you used had been animal cells instead of plant cells? EXPLAIN
your answer!
Analysis- Part B: Macroscopic Observations (Carrots and eggs)
1. What type of solution were the eggs in that were in vinegar? What directions were the water
molecules moving when the eggs were in vinegar? Draw a picture.
2. What type of solution were the carrots and eggs in that were in distilled water? What direction were
the water molecules moving when the carrots and eggs were in the distilled water? Draw a picture.
3. What type of solution were the carrots in that were in salt water and the eggs in that were in corn
syrup? What direction were the water molecules moving when the carrots and eggs were in these
solutions? Draw a picture.
4. This type of diffusion is called ____________________________.