Partial permeability in plant cell structures

Steps:

• Partial permeability means membranes allow selective passage of substances like water but block solutes like salt ions.
• In a concentrated salt solution, water exits the cell via osmosis, causing plasmolysis, visible at the plasma membrane.
• Typical plant cell diagram labels: 1 as cell wall (freely permeable to all), 2 as plasma membrane (selectively permeable), 3 as vacuole or cytoplasm (not a membrane).
• Only the plasma membrane (2) shows partial permeability, as it regulates ion and water movement during the 10-minute exposure.

Why D is correct:

• The plasma membrane (2) is defined as partially permeable, following the fluid mosaic model, allowing osmosis but restricting salt diffusion.

Why the others are wrong:

• A: Includes 1 (cell wall), which is fully permeable to salts and water.
• B: Includes 1 (cell wall, fully permeable) and 3 (vacuole membrane or cytoplasm, not primarily permeable in this context).
• C: 1 (cell wall) is fully permeable, not selective.

Final answer: D