Question

The osmotic expansion of a cell kept in water is chiefly regulated by

• A. Plastids
• B. Vacuoles
• C. Ribosomes
• D. Mitochondria

Answer 1

The correct option is B

Vacuoles

The correct option is B.

Explanation of correct option:

1. Vacuoles in plant cells aid in preserving the equilibrium of water. They significantly contribute to cellular osmotic expansion.
2. A cytoplasmic region that is membrane-bound is called a vacuole. They are cytoplasmic but non-cytoplasmic areas that are separated from the latter by tonoplast.
3. They are thought to have been created by pinching off and growing from ER. Plant cells have a big central vacuole and a number of smaller vacuoles.

Explanation of incorrect options

Option A

1. Plastids are kept in cells by multiplying before cell division and splitting into each daughter cell during cell division. It is unknown, nevertheless, if suppressing plastid division results in the production of cells devoid of plastids.

Option C

1. The ribosomal protein (RP) gene's expression varies as a result of osmotic stress. The stability of the RP pre-mRNA is required for both the RP gene transcription rate (TR) by RNA polymerase and the RP pre-mRNA splicing and degradation rates.
2. The RP mRNA created during splicing can either be utilized or destroyed to create ribosomal proteins during translation. Osmotic stress lowers the RP gene's TR, which accelerates the degradation of RP pre-mRNA.

Option D

1. Oxidative stress causes non-selective permeability transition pores (PTP) in the inner mitochondrial membrane to open. Persistent PTP opening results in mitochondrial enlargement because of elevated colloid osmotic pressure in the matrix, which is followed by mitochondrial membrane depolarization and ATP hydrolysis.
2. The primary cause of both apoptosis and necrosis, which are both mitochondria-mediated cell death processes, is mitochondrial swelling.

Final answer: The osmotic expansion of a cell kept in water is chiefly regulated by vacuoles.