Question

The osmotic expansion of cell kept in water is chiefly regulated by
A. Mitochondria
B. Vacuoles
C. Plastids
D. Ribosomes

Answer 1

The pressure needed to stop the net flow of water through the plant cell membrane is reflected by the osmotic potential. Water flows through the cell as the osmotic pressure within the cell is greater than that outside the cell.

Complete answer:
Mitochondria: In both cell survival and cell death, mitochondria play a significant role. Non-selective permeability transition pores (PTP) in the inner mitochondrial membrane undergo opening in response to oxidative stress. Due to increased colloid osmotic pressure in the matrix, followed by mitochondrial membrane depolarization and ATP hydrolysis, persistent PTP opening causes mitochondrial swelling. The key factor contributing to mitochondria-mediated cell death by both apoptosis and necrosis is mitochondrial swelling.
Vacuoles: The membrane-bound space located in the cytoplasm is the vacuole. They are non-cytoplasmic areas within the cytoplasm, isolated by tonoplast from the latter. They are thought to be created from ER by expansion and pinching off. In plant cells, a large central vacuole and several tiny vacuoles occur. They play a major role in cellular osmotic expansion.
Plastids: By proliferating prior to cell division and being split during cell division into each daughter cell, plastids are retained in cells. However, it is unclear whether cells without plastids are produced when the division of plastids is suppressed.
Ribosomes: Scheme of changes in the expression of the ribosomal protein (RP) gene upon osmotic stress. Both the RP gene transcription rate (TR) by RNA polymerase and the RP pre-mRNA splicing and degradation rates depend on the RP pre-mRNA steady state. The RP mRNA formed by splicing can be used or sent to degradation for the synthesis of ribosomal proteins by translation. Osmotic stress induces a decrease in the TR of the RP gene and a dependent rise in the degradation rate of the RP pre-mRNA.

Hence, the correct answer is (B).

Note:
Cytoplasmic osmoregulatory processes in plants are little known, and much less is understood as to how the osmotic properties of the cytoplasm and organelles are organised. Few findings indicate that osmotic imbalance through the plastid envelope can elicit a response comparable to that elicited through the plasma membrane by osmotic imbalance and provide evidence of the incorporation of an organelle 's osmotic state into that of the cell in which it resides.