Osmosis & Diffusion in an Egg
Cells use their cell membranes as selective “doors”, allowing substances to pass through by
several different means. Passive processes are those which allow substances to pass without using
any cellular energy from ATP. Osmosis is a passive process in which water is driven into or out of a
cell by pressure due to the concentration gradient (amount of solutes dissolved in the water). The
water will move in or out in order to have an equal concentration of solute on each side of the cell
membrane. The solution concentration affects tonicity (shape or tone). Different concentrations
have different effects on cells. In the lab below, you will use an egg as a model for osmosis in cells.
Type of solution
Hypertonic
Concentration of solutes
Solution outside > solution in cells
Effect on cell
Cells release water and crenate(shrink)
Hypotonic
Solution outside < solution in cells
Cells bloat and possibly burst(lysis)
Isotonic
Solution outside = solution in cells
No change in cell shape
Objective:
In this investigation, you will use a fresh hen's egg to determine what happens
during osmosis & diffusion across membranes.
Materials: (per lab group)
1 egg, masking tape & marker, cup, distilled water, clear sugar syrup (Karo,
for example), vinegar, electronic balance, paper towels, paper, pencil
Procedure:
Day 1
1. Label the cup with the names or initials of everyone in your lab group &
the word "vinegar".
2. Mass the egg with the electronic balance & record in the data table.
3. Carefully place the raw egg into the cup & cover the egg with vinegar.
4. Place the cup in the back of the room to sit for 24 to 48 hours until
the outer calcium shell is removed.
Day 2
1. Carefully pick up your cup and take it to your lab station.
2. Carefully pour the vinegar out of the cup, gently remove the egg, rinse
3.
4.
5.
6.
7.
it with water, and blot it dry with paper towels.
Record the size & appearance of your egg in your data table.
Mass the egg on an electronic balance & record.
Clean and re-label the cup with your lab group names & the word
"distilled water".
Carefully place the egg into the cup & cover the egg with distilled
water.
Place the cup in the back of the room allow it to sit for 24 hours.
Day 3
1. Carefully pick up your cup and take it to your lab station.
2. Carefully pour the distilled water out of the cup, gently remove the egg,
3.
4.
5.
6.
7.
and blot it dry with paper towels.
Record the size & appearance of your egg in your data table.
Mass the egg on an electronic balance & record.
Clean and re-label the cup with your lab group names & the word
"syrup".
Carefully place the egg into the cup & cover the egg with clear syrup.
Place the cup in the back of the room allow it to sit for 24 hours.
Day 4
1. Carefully pick up your cup and take it to your lab station.
2. Carefully pour the syrup out of the cup, gently remove the egg, rinse it
with water, and blot it dry with paper towels.
3. Record the size & appearance of your egg in your data table.
4. Mass the egg on an electronic balance & record.
5. Clean up your work area & put away all lab equipment.
Data:
Hypothesis Day1:
Hypothesis Day 2:
Hypothesis Day 3:
RESULTS OF DIFFUSION
Original
Final Mass Appearance of Egg
Mass
Hypertonic,
Hypotonic,
Isotonic?
VINEGAR
WATER
SYRUP
Questions & Conclusion:
1. Vinegar is made of acetic acid & water. Explain how it was able to remove
the calcium shell.
2. (a) What happened to the size of the egg after remaining in vinegar?
(b) Was there more or less liquid left in the jar?
(c) Did water move into or out of the egg? Why?
3. (a) What happened to the size of the egg after remaining in distilled
water?
(b) Was there more or less liquid left in the jar?
(c) Did water move into or out of the egg? Why?
4. (a) What happened to the size of the egg after remaining in syrup?
(b) Was there more or less liquid left in the jar?
(c) Did water move into or out of the egg? Why?
5. Was the egg larger after remaining in water or vinegar? Why?
6. Why are fresh vegetables sprinkled with water at markets?
7. In this lab, what is the independent variable? Dependent variable?
Controlled Variables(Constants)?