Investigating Osmosis: Exploring the Flow of Water

Osmosis is a fascinating process that keeps plants and animals alive. But how can we see it in action? By performing simple experiments, we can explore how osmosis works and its effects on living cells.

 

How to Investigate Osmosis

Investigate Osmosis Using Dialysis Tubing

• This experiment simulates osmosis through a membrane.
• The Dialysis tubing is a partially permeable membrane made from cellulose. This can simulate a cells membrane
• The holes in the Dialysis membrane are small enough that they prevent larger molecules like sucrose passing through but allow smaller molecules, glucose and water, to pass through by osmosis and diffusion

Method:

1. Prepare Dialysis Tubing: Soak tubing in water and tie one end to create a bag.

2. Fill Tubing: Fill the tubing with a sugar solution and tie the other end.

3. Immerse in Beaker: Place the tubing in a beaker of distilled water.

4. Observe Changes: After 30 minutes, check for changes in the volume or mass of the tubing.

Expected Results:

• Water moves into the tubing (high water potential outside, low inside), causing it to swell.

 

 

Effects of Osmosis on Plant Tissues

Plant cells respond to osmosis differently based on the surrounding solution:

Hypotonic Solution (Dilute):

• Water enters the cells.

• Cells become turgid due to increased turgor pressure.

Isotonic Solution (Balanced):

• Water moves in and out at the same rate.

• Cells remain in their normal state.

Hypertonic Solution (Concentrated):

• Water leaves the cells.

• Cells become flaccid, and severe loss causes plasmolysis

 

Investigate Immersing Plant Tissues in Solutions of Different Concentrations

• This experiment involves cutting pieces of root vegetable i.e a potato, and placing in distilled water and sucrose solutions of different concentrations
• The pieces of vegetable are weighted before immersing into the solutions
• They are then left in the solutions for 20 - 30 minutes, removed and excess liquid is dried of and removed before weighing again

 

 

If the piece of vegetable loses mass:

• Water has moved out of the vegetable piece and into the surrounding solution by osmosis
• This means that the surrounding solution must be more concentrated than the vegetables

If the piece of vegetable gains mass:

• Water has moved into the vegetable piece from the surrounding solution by osmosis
• This means that the surrounding solution must be less concentrated than the vegetables

If the piece of vegetable has no change in mass:

• Water has not moved into or out of the vegetable piece
• This means that the surrounding solution must have the same concentration as the vegetable piece