Which transport mechanisms are classified as passive mechanisms?

• A. Facilitated diffusion and active transport
• B. Endocytosis and exocytosis
• C. Sodium-potassium pump and phagocytosis
• D. Diffusion and osmosis

Answer: (D)

Verified step by step guidance

1. Understand the concept of passive transport: Passive transport mechanisms do not require energy input from the cell. They rely on the natural movement of molecules from areas of higher concentration to areas of lower concentration.
2. Identify diffusion: Diffusion is a passive transport mechanism where molecules move from an area of high concentration to an area of low concentration until equilibrium is reached. This process does not require energy.
3. Identify osmosis: Osmosis is a specific type of diffusion that involves the movement of water molecules across a selectively permeable membrane. Water moves from an area of low solute concentration to an area of high solute concentration, balancing solute concentrations on both sides of the membrane.
4. Differentiate from active transport: Active transport mechanisms, such as the sodium-potassium pump, require energy (usually in the form of ATP) to move molecules against their concentration gradient, from low to high concentration.
5. Recognize other passive mechanisms: Facilitated diffusion is another passive transport mechanism where molecules move across cell membranes through protein channels, without energy input, following their concentration gradient.