Florida Biology EOC Practice Test

What describes the movement of water across a selectively permeable membrane?

1. Active transport

2. Diffusion

3. Osmosis

4. Phagocytosis

The correct answer is: Active transport

The correct answer is the process known as osmosis. Osmosis specifically refers to the movement of water molecules across a selectively permeable membrane. This movement occurs from an area of lower solute concentration to an area of higher solute concentration, effectively equilibrating solute concentrations on both sides of the membrane. Active transport, in contrast, involves the movement of substances across a membrane against their concentration gradient, requiring energy input, usually in the form of ATP. This is different from the passive movement of water in osmosis, which does not require energy. Diffusion refers to the movement of solutes from areas of high concentration to areas of low concentration and is a general term that does not specifically involve water movement. While water can diffuse, osmosis is the more precise term for its behavior across a selectively permeable membrane. Phagocytosis is a cellular process used to engulf large particles or cells and is not related to the movement of water. It involves cell membrane folding around the particle, encapsulating it in a vesicle, which is not relevant to the simple movement of water. Thus, osmosis accurately describes the movement of water across selectively permeable membranes, distinguishing it from these other processes.