What organelles are activated to pump water out of the cell?
A.
Free ribosomes.
B.
Contractile vacuoles.
C.
Mitochondria.
D.
Microtubules.
The Correct answer and Explanation is:
The correct answer is B. Contractile vacuoles.
Explanation:
Contractile vacuoles are specialized organelles primarily found in some single-celled organisms, such as protists (e.g., paramecia and amoebae) and certain types of algae. Their primary function is to regulate osmotic pressure within the cell by expelling excess water that enters due to the process of osmosis. In freshwater environments, where the concentration of solutes is lower outside the cell than inside, water naturally flows into the cell, causing it to swell. Without a mechanism to remove this excess water, the cell could eventually burst due to the pressure.
The contractile vacuole operates by accumulating water from the cytoplasm. Once filled, it contracts rhythmically, forcing the water out of the cell through a pore in the plasma membrane. This process not only prevents cell lysis (bursting) but also helps maintain homeostasis, ensuring the cell maintains a balance of solutes and water. The activity of the contractile vacuole is crucial for the survival of cells in hypotonic environments, where water influx is a constant challenge.
In contrast, the other options do not play roles in pumping water out of cells. A. Free ribosomes are involved in protein synthesis and do not manage water levels. C. Mitochondria are the energy-producing organelles of the cell, generating ATP through cellular respiration, but they do not have a direct role in water regulation. D. Microtubules are part of the cytoskeleton and contribute to cell shape and transport but are not involved in the expulsion of water. Thus, contractile vacuoles are essential for the osmoregulatory processes in certain organisms, enabling them to thrive in diverse aquatic environments.