Which of the following is an active transport process?

• A. Osmosis
• B. Simple diffusion
• C. Facilitated diffusion
• D. Sodium-potassium pump

Answer: (D)

Verified step by step guidance

1. Understand the concept of active transport: Active transport is a process that requires energy to move substances across cell membranes against their concentration gradient. This is different from passive transport, which does not require energy.
2. Identify the processes listed: Osmosis, simple diffusion, and facilitated diffusion are all passive transport processes. They move substances from areas of higher concentration to areas of lower concentration without the use of energy.
3. Recognize the sodium-potassium pump: The sodium-potassium pump is a well-known example of active transport. It uses energy from ATP to move sodium ions out of the cell and potassium ions into the cell, against their respective concentration gradients.
4. Compare the processes: Note that osmosis involves the movement of water across a membrane, simple diffusion involves the movement of molecules directly through the lipid bilayer, and facilitated diffusion involves the movement of molecules through a membrane protein, all without energy.
5. Conclude that the sodium-potassium pump is the active transport process among the options given, as it requires energy to function.