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Gummy Bear Lab – Bio Sci
Introduction: We will study the movement of water
across a membrane, osmosis. We will see if we can get
water to permeate (enter) a gummy bear as a model of
water moving across a cell’s membrane. Recall that the
inside of a living organism’s cell’s lipid bilayer is
hydrophobic, or “water hating.” Because of this, water
molecules have a tough time passing through the cell
membrane. However, many cells contain water channel
proteins, known as aquaporins that allow water to pass
right through them, as shown in Figure 7-17. This is an
example of facilitated diffusion, the movement of a
substance across a membrane through a channel protein
without requiring energy. The movement of water
through cell membranes by facilitated diffusion is an
Figure 7-17 Osmosis of water across a
selectively permeable membrane through
the channel protein aquaporin.
extremely important biological process – the process of osmosis. In osmosis, as in other forms
of diffusion, molecules move from an area of higher concentration to an area of lower
concentration. The only difference is molecules that move in osmosis are water molecules, not
solute molecules (particles in the solution inside or outside the cell). The process of osmosis is
shown in Figure 7-17. Water will tend to move across the membrane from high to low
concentration until equilibrium is reached. At that point, the concentrations of water and
solute (sugar in this case) will be the same on both sides of the membrane.
Prelab Questions:
1. Define osmosis and facilitated diffusion from this lab, your notes, or textbook.
2. Why does water have a hard time moving across the membrane?
3. Water will move from high to low concentrations until what happens?
Purpose: To study osmosis in a cell model (analogy) – gummy bears.
Hypothesis: If water can permeate the gummy bear then
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Materials:
Water
Balance
Gummy Bear
Container
Ruler
Procedure: Each 2 person group of students will use one color gummy bear to test osmosis.
Day 1: Soaking the gummy bear in water overnight.
1. Pre-soaking measurements. Record all measurements in Data Table 1.
a. Measure the length of your gummy bear from the top of its head to the bottom
of its feet to the nearest centimeter.
b. Measure the width of your gummy bear across the back of the bear to the
nearest centimeter.
c. Measure the thickness of your gummy bear from the back to the front (down the
side) to the nearest centimeter.
d. Calculate volume – multiply length, width, & thickness. Round to two decimal
places.
e. Measure the mass using the electronic balance to one decimal place.
2. Place the gummy bear in a cup labeled with your name and class period. Add 50mL of
water to the cup and allow it to sit overnight.
Day 2: Measuring gummy bear for evidence of osmosis after soaking in water overnight.
3. On day 2, remove the gummy bear CAREFULLY from the cup of water, lay on a paper
towel.
4. Repeat the measurements from Day 1, step 1.
5. Rinse and dry your cup.
6. Throw your gummy bear in the garbage.
7. Determine the amount of change for each measurement (Change 1-2) in Data Table 1.
Data Collection:
Data Table 1 Gummy Bear Measurements
Day
Color
Length
Width
Thickness
Volume
Mass
1
2
Change
(Days 1-2)
Data Table 2 Gummy Bear Color Difference. Record your gummy bear color and mass change
for Days 1-2 in addition to 3 other colors and mass change for other groups’ gummy bears.
Gummy Bear
Color
Mass Change
(Days 1-2)
Data Analysis:
Construct a bar graph from Data Table 2 info; Gummy Bear Color Vs. Mass Change (Days 1-2).
Please answer the following question IN COMPLETE SENTENCES!!!.
1. Days 1-2 Which measurement change is greater – volume or mass? Explain.
2. Days 1-2 Was a major difference evident in mass change between the gummy bear
colors? Do you think gummy bear color has an effect on the osmosis of that gummy
bear? Explain.
3. Was your hypothesis supported? Explain.
4. Did water enter or leave the gummy bear? Why did this happen? (MUST EXPLAIN
THIS IN TERMS OF OSMOSIS).