Veterinary Technician Practice Exam

What term describes the movement of a substance through and across cell membranes?

1. Diffusion

2. Filtration

3. Osmosis

4. Active Transport

The correct answer is: Osmosis

The correct term that describes the movement of a substance through and across cell membranes is osmosis. Osmosis specifically refers to the passive movement of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration until equilibrium is reached. This process is essential for maintaining fluid balance within cells and the overall homeostasis of an organism. Other terms like diffusion, filtration, and active transport describe different mechanisms. Diffusion is the movement of any substance from an area of higher concentration to an area of lower concentration and can occur with various types of molecules, not just water. Filtration involves the movement of water and solutes through a membrane due to hydrostatic pressure, typically observed in the kidneys. Active transport is the movement of substances against their concentration gradient, which requires energy, often in the form of ATP, to pump molecules from lower to higher concentrations.