Transportation of materials through Plasma Membrane — Important Questions

Diffusion

Diffusion is the process by which substances spread equally throughout a medium due to random molecular motion. When coffee powder is added to water, the coffee particles move from areas of high concentration to areas of low concentration until they are evenly distributed. This happens without any membrane involvement. Osmosis specifically involves water movement across membranes, filtration involves separation through barriers, and evaporation is the conversion of liquid to gas.

It shrinks

When a swollen raisin is placed in concentrated sugar solution, it shrinks because water moves out of the raisin through osmosis. The sugar solution has a higher solute concentration than the inside of the raisin, so water moves from the raisin (lower solute concentration) to the sugar solution (higher solute concentration). This process is called exosmosis, where water exits the cell, causing it to shrink.

Endosmosis

Endosmosis is the specific term for the process where water molecules enter a cell through the plasma membrane. This happens when the cell has a higher solute concentration than its surroundings, causing water to move inward. Exosmosis is the opposite process where water leaves the cell. Diffusion is the general movement of particles, and filtration is a mechanical separation process.

Water molecules

Water molecules are small and can easily pass through the plasma membrane through tiny water channels. The plasma membrane allows water to pass freely due to its small size and neutral charge. Large protein molecules, starch molecules, and cellulose fibers are too large to pass through the membrane easily and would require special transport mechanisms. The size and chemical properties of molecules determine their ability to cross membranes.