Question

Osmoregulation of internal environment of a cell is chiefly regulated by
A) Vacuoles
B) Plastids
C) Ribosomes
D) Mitochondria

Answer 1

Hint: Contractile vacuoles are membrane-bound organelles which participate in osmoregulation by pumping water out of the cell.

Complete Answer:
1) Vacuoles: The osmoregulation is regulated by the vacuoles which stores a large amount of water as well as minerals. They have function to maintain the solvent or solute balance within a cell by a process called osmoregulation.
2) Ribosomes are machinery for protein synthesis.
3) Plastids are organelles with double-membranes and are found in cells of both plants as well as algae. They are responsible for manufacturing and storing food. They are also found to contain pigments which can be used in the process of photosynthesis as well as there are different types of pigments which can change the cell colour.
4) Mitochondria are the organelles involved in energy generation in the form of ATP for the cell by the process of oxidative phosphorylation.

So the correct answer is (A) Vacuoles.

Additional Information:
A vacuole is a single membrane-bound cell organelle. In animal cells they are small and help storage of waste products while in plant cells, vacuoles help in maintaining water balance. The membrane of vacuole is called tonoplast.

Note: Contractile vacuoles are the special types of vacuoles which are present in an unicellular organism like Paramoecium as well as multicellular organisms like sponges and hydras. These vacuoles are responsible for maintaining cell osmolarity by pumping out water. When water concentration increases inside the cell, these vacuoles perform active contraction to remove it.