Vacuoles

You can see how the lipid membranes around the cell and around the vacuoles seal themselves off using soap bubbles. Soap bubbles are a kind of lipid membrane. They're not exactly the same as cell membranes, but they're made of fat molecules and they act the same way.

To do this experiment, first put some soap bubble liquid in a shallow tray (a roasting pan or cookie sheet will be fine), about 1 or 2 cm deep. Now make a soap bubble frame. Take two straws short enough to fit in your tray, and run cotton kitchen string through the straws so that you get a rectangle (two sides straws, two sides string). Make sure the knot is inside one of the straws.

Lay your frame in the bubble liquid so that it makes a lipid membrane. Lift the frame out and see how the cell can twist and turn without breaking the membrane.

Make a circle of sewing thread. Gently lay the thread circle on your lipid membrane. Poke a hole inside the circle with a pencil or stick. Now you have a lipid membrane with a hole in it. To see how lipid membranes seal themselves up, gently lift the thread circle up.

How to blow a bubble inside a bubble

Can you get your membrane to form a spherical bubble? Now see whether you can get a bubble to form inside another bubble, the way a vacuole forms inside a cell.