Arizona State University (ASU) BIO181 General Biology I Exam 1 Practice

The primary function of a contractile vacuole in paramecium is to regulate osmotic pressure. Paramecium are unicellular organisms that live in freshwater environments, where the concentration of solutes in their surroundings is lower than that inside their cells. This leads to water constantly flowing into the cell via osmosis.

To maintain the balance of water and prevent the cell from swelling and potentially bursting, the contractile vacuole collects excess water that enters the cell. The vacuole then periodically contracts to expel this water out of the cell, thus preventing lysis and helping to maintain homeostasis. This active regulation of osmotic pressure is crucial for the survival of paramecium in hypotonic environments.

In contrast, photosynthesis does not occur in paramecium as they are not photosynthetic organisms, and waste storage is managed differently, typically involving different cellular structures depending on the type of waste. Similarly, although protein synthesis is vital for all living cells, it is not the function associated specifically with contractile vacuoles.