Which of the following is an example of secondary active transport?

• A. Sodium-potassium pump
• B. Osmosis
• C. Sodium-glucose cotransporter
• D. Facilitated diffusion of glucose

Answer: (C)

Verified step by step guidance

1. Understand the concept of secondary active transport: Secondary active transport involves the movement of molecules across a cell membrane using energy indirectly derived from ATP. It relies on the electrochemical gradient created by primary active transport.
2. Identify the role of the sodium-potassium pump: The sodium-potassium pump is an example of primary active transport, which directly uses ATP to transport sodium and potassium ions across the cell membrane, creating an electrochemical gradient.
3. Recognize the function of osmosis: Osmosis is the passive movement of water molecules across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration. It does not require energy and is not a form of active transport.
4. Understand facilitated diffusion: Facilitated diffusion is a passive transport process where molecules move across the cell membrane through protein channels or carriers, down their concentration gradient, without the use of energy.
5. Identify the sodium-glucose cotransporter as secondary active transport: The sodium-glucose cotransporter uses the energy from the sodium gradient, established by the sodium-potassium pump, to transport glucose into the cell against its concentration gradient. This is an example of secondary active transport.