Plasma Membrane Movement Quiz

Diffusion is the movement of molecules from a region of higher concentration to one of lower concentration. This movement occurs because the molecules are constantly colliding with one another. The net movement of the molecules is away from the region of high concentration to the region of low concentration. The driving force for diffusion is the concentration gradient, which is the difference in concentration of a substance between two areas.

Osmosis is the movement of water from a region of higher concentration to one of lower concentration. Osmosis occurs across a membrane that is semipermeable. A semipermeable membrane lets only certain molecules pass through while keeping other molecules out, allowing the movement of water across the membrane.

Both diffusion and osmosis involve the movement of molecules from a region of higher concentration to one of lower concentration. Diffusion involves the movement of any type of molecule, while osmosis specifically refers to the movement of water molecules. Additionally, osmosis occurs across a semipermeable membrane, whereas diffusion can occur through any permeable membrane or even in open space.

Facilitated diffusion is a mechanism for movement across the plasma membrane that involves the assistance of transport proteins. These proteins facilitate the movement of specific molecules across the membrane. An example of a molecule that undergoes facilitated diffusion is glucose, which requires transport proteins to move through the membrane.

A drop of dye placed in a beaker of water illustrates diffusion as the dye molecules spread out and color the water. This demonstrates the movement of dye molecules from an area of higher concentration (the drop) to an area of lower concentration (the surrounding water).