Question

Which of the following structures is porous and semi-permeable?
A. Cell wall
B. Cell membrane
C. Chromosome
D. None of the above

Answer 1

Hint: The semi-permeable membrane only allows ions to travel through it from the lower concentration region to the higher concentration region. The motion varies for different factors, such as temperature, friction, etc.

Complete answer: The outermost covering of cells, organelles, etc. is the cell membrane. For the entry and exit of the various metabolites and other substances in and out of these cells and the cell organelles, the membrane provides a passage. The cell includes some compounds, although some have no use in the cell. The membrane has a specific function for filtering between certain particles or substances. It allows only those substances that are required by the cell to be entered while holding the others back. On the inner side of the cell, the same happens via this membrane, excretory matter, and other substances that the cell does not need are thrown out of the cell, while those that the cell cannot afford to lose are kept. The cellular membrane is thus semi-permeable. A porous membrane which forms the boundary of the cell cytoplasm is the cell membrane or the plasma membrane. It only permits those molecules in or out of the cell, as it is porous, so it is called a semi-permeable membrane.
Hence, the correct answer is option B-Cell membrane.

Note: Semi-permeable membranes are often confused with selectively permeable membranes. Both are two distinct things. While semi-permeable membranes allow certain solutes but almost all solvents to move through them, the solvents and some solvent particles can also be kept back by selectively-permeable membranes.