What powers the sodium-glucose symporter in active transport?

• A. Glucose concentration gradient
• B. ATP directly
• C. The sodium ion gradient
• D. Potassium ion gradient

Answer: (C)

Verified step by step guidance

1. Understand the concept of active transport: Active transport is a process that moves molecules across a cell membrane against their concentration gradient, requiring energy.
2. Identify the role of the sodium-glucose symporter: This symporter uses the energy from the sodium ion gradient to transport glucose into the cell.
3. Explain the sodium ion gradient: The sodium ion gradient is established by the sodium-potassium pump, which uses ATP to move sodium ions out of the cell and potassium ions into the cell.
4. Clarify why ATP is not directly used: While ATP is used to maintain the sodium ion gradient, it does not directly power the symporter. Instead, the energy from the gradient itself is used.
5. Summarize the process: The sodium-glucose symporter relies on the sodium ion gradient created by the sodium-potassium pump to facilitate the active transport of glucose into the cell.