Which process is considered an example of primary active transport?

Which process is considered an example of primary active transport?

• A. The movement of glucose down its concentration gradient.
• B. The Na+/K+ pump.
• C. The Na+/glucose cotransporter.
• D. Facilitated diffusion of ions.

Answer: (B)

Primary active transport is a process that directly utilizes energy, typically in the form of ATP, to move ions or molecules against their concentration gradient. The Na+/K+ pump serves as a classic example of this process. In the case of the Na+/K+ pump, this membrane protein transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. It does so by using ATP to fuel the transport mechanism, moving Na+ against its concentration gradient (out of a region of higher concentration within the cell to a lower concentration outside) and K+ against its concentration gradient (into the cell from a lower concentration outside). This active transport process is crucial for maintaining the electrochemical gradients across the cell membrane, which are essential for various cellular functions, including nerve impulse transmission and muscle contraction. Other processes listed do not represent primary active transport. The movement of glucose down its concentration gradient is a passive process, as it relies on diffusion without energy input. The Na+/glucose cotransporter involves secondary active transport, which relies on the gradient established by the Na+/K+ pump but does not utilize ATP directly for its function. Finally, facilitated diffusion of ions also occurs down their concentration gradients and does not require energy.

Primary active transport is a process that directly utilizes energy, typically in the form of ATP, to move ions or molecules against their concentration gradient. The Na+/K+ pump serves as a classic example of this process.

In the case of the Na+/K+ pump, this membrane protein transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell. It does so by using ATP to fuel the transport mechanism, moving Na+ against its concentration gradient (out of a region of higher concentration within the cell to a lower concentration outside) and K+ against its concentration gradient (into the cell from a lower concentration outside). This active transport process is crucial for maintaining the electrochemical gradients across the cell membrane, which are essential for various cellular functions, including nerve impulse transmission and muscle contraction.

Other processes listed do not represent primary active transport. The movement of glucose down its concentration gradient is a passive process, as it relies on diffusion without energy input. The Na+/glucose cotransporter involves secondary active transport, which relies on the gradient established by the Na+/K+ pump but does not utilize ATP directly for its function. Finally, facilitated diffusion of ions also occurs down their concentration gradients and does not require energy.