Question

A sodium-potassium pump within a cell membrane requires energy to move sodium and potassium ions into or out of a cell. The movement of glucose into or out of a cell does not require energy. Which statement best describes the movement of these materials across a cell membrane? *
1 point
Sodium and potassium ions move by active transport, and glucose moves by osmosis.
Sodium and potassium ions move by active transport, and glucose moves by facilitated diffusion.
Sodium and potassium ions move by facilitated diffusion, and glucose moves by osmosis.
Sodium and potassium ions move by facilitated diffusion, and glucose moves by active transport.

Answer 1

The correct answer is: Sodium and potassium ions move by active transport, and glucose moves by facilitated diffusion.

Because sodium and potassium are moved through cell membrane against their concentration gradients, transport requires energy (ATP), so it is active. Glucose is a polar molecule and because the plasma membrane is impermeable to polar molecules transport of this important nutrient is accomplished by carrier proteins. This process is called facilitated diffusion and it is passive transport (doesn’t require energy).