what is an analogy for a vacuole?
If your talking about a contractile vacuole like in some protists, a sponge would be a good analogy. The water enters as per osmosis and in order to keep its environment perfect, the paramecium or whatever squeezes the sponge and out goes the water. It is important to note that not all vacuoles are for water, there are food vacuoles and enzyme vacuoles, basically they are sacks for cellular storage.
