Contractile vacuole

Definition

A contractile vacuole is a specialized organelle in certain unicellular eukaryotes that expels excess water to maintain osmotic balance. It plays a crucial role in osmoregulation, especially in freshwater environments.

5 Must Know Facts For Your Next Test

1. Contractile vacuoles are primarily found in freshwater protozoans and algae.
2. They help prevent the cell from bursting due to osmotic pressure by periodically expelling water.
3. The process involves the vacuole filling with water and then contracting to release the water outside the cell.
4. Contractile vacuoles are essential for survival in hypotonic environments where water continuously enters the cell by osmosis.
5. The activity of contractile vacuoles is often coordinated with other cellular structures and systems, such as the cytoskeleton and ion channels.

Review Questions

• What is the primary function of a contractile vacuole?
• In which type of environments are contractile vacuoles especially important?
• How does a contractile vacuole contribute to osmoregulation in unicellular eukaryotes?

Related terms

Osmoregulation: The process by which cells and organisms maintain fluid balance and concentration of solutes.

Protozoans: A diverse group of single-celled eukaryotic organisms, many of which have contractile vacuoles.

Hypotonic Environment: An environment where the extracellular fluid has a lower concentration of solutes compared to the intracellular fluid, leading to water influx into cells.