Vernier Software and Technology
Vernier Software & Technology

Biological Membranes

Figure from experiment 9 from Biology with Vernier


The primary objective of this experiment is to determine the stress that various factors, such as osmotic balance, detergents, and pH, have on biological membranes. Membranes within cells are composed mainly of lipids and proteins. They often serve to help maintain order within a cell by containing cellular materials.

One type of vacuole in the cells of plants, the tonoplast, is quite large and usually contains water. In beet plants, this membrane-bound vacuole also contains a water soluble red pigment, betacyanin, that gives the beet its characteristic color. Since the pigment is water soluble and not lipid soluble, it is contained in the vacuole when the cells are healthy. If the integrity of a membrane is disrupted, however, the contents of the vacuole will spill out into the surrounding environment and color it red. This usually means the cell is dead. If beet membranes are damaged, the red pigment will leak out into the surrounding environment. The intensity of color in the environment should be proportional to the amount of cellular damage.

You will test the effect of osmotic balance, detergents, and pH changes on biological membranes. The presence of certain salts is essential for most plant growth, but too much salt can kill plants. Even salts that are not transported across cell membranes can affect plants—by altering the osmotic balance. Osmosis is the movement of water across a semipermeable membrane from a region of low solute concentration to a region of higher solute concentration. It can greatly affect a cell’s water content when the amount of water inside the cell is different than the amount outside the cell. You will test to see how this osmotic stress affects the cellular membrane integrity.


In this experiment, you will

  • Use a Colorimeter to measure color changes due to disrupted cell membranes.
  • Determine the effect of osmotic balance on biological membranes.
  • Determine the effect of detergents on biological membranes.
  • Determine the effect of pH on biological membranes.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Option 1

Option 2

Option 3

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Biology with Vernier »

Biology with Vernier

See other experiments from the lab book.

1Energy in Food
2Limitations on Cell Size: Surface Area to Volume
3Acids and Bases
4Diffusion through Membranes
5Conducting Solutions
6AEnzyme Action: Testing Catalase Activity
6BEnzyme Action: Testing Catalase Activity
8The Effect of Alcohol on Biological Membranes
9Biological Membranes
11ACell Respiration (O2)
11BCell Respiration (CO2)
11CCell Respiration (Pressure)
11DCell Respiration (CO2 and O2)
12ARespiration of Sugars by Yeast
12BSugar Fermentation
13Population Dynamics
14Interdependence of Plants and Animals
15Biodiversity and Ecosystems
16AEffect of Temperature on Respiration
16BEffect of Temperature on Fermentation
17Aerobic Respiration
18Acid Rain
19Dissolved Oxygen in Water
20Watershed Testing
21Physical Profile of a Lake
23AEffect of Temperature on Cold-Blooded Organisms
23BEffect of Temperature on Cold-Blooded Organisms
24ALactase Action
24BLactase Action
25Primary Productivity
26Control of Human Respiration
27Heart Rate and Physical Fitness
28Monitoring EKG
29Ventilation and Heart Rate
30Oxygen Gas and Human Respiration
31APhotosynthesis and Respiration (O2)
31BPhotosynthesis and Respiration (CO2)
31CPhotosynthesis and Respiration (CO2 and O2)

Experiment 9 from Biology with Vernier Lab Book

<em>Biology with Vernier</em> book cover

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