Q: Which correctly describes how the sodium-potassium pump works?
A: ATP provides energy, pump transports the two types of ions.
To understand how the sodium-potassium pump works, let's break it down into the following components:
1. Energy Source: The sodium-potassium pump is an active transport mechanism that requires energy to function. This energy is provided by a molecule called ATP (adenosine triphosphate).
2. Pump Structure: The pump itself is a protein complex located in the cell membrane. It consists of several subunits that work together to facilitate the transport of sodium (Na+) and potassium (K+) ions across the cell membrane.
3. Ion Transport: The pump uses energy from ATP to move three sodium ions out of the cell, while simultaneously moving two potassium ions into the cell. This process occurs against their concentration gradients, meaning that it moves the ions from an area of lower concentration to an area of higher concentration.
4. Binding and Release: The pump has specific binding sites for sodium and potassium ions. When three sodium ions bind to the pump from the inside of the cell, ATP is hydrolyzed (broken down) into ADP (adenosine diphosphate) and inorganic phosphate (Pi). This releases energy, which causes a conformational change in the pump, allowing it to "flip" and release the sodium ions to the outside of the cell.
5. Potassium Binding and Release: With the binding sites now facing the outside of the cell, two potassium ions from the extracellular environment bind to the pump. This binding triggers a phosphate group from the hydrolyzed ATP to be released, causing another conformational change in the pump. This change allows the potassium ions to be released inside the cell.
6. Resetting and Repeated Process: Once the potassium ions are released, the pump returns to its initial conformation, ready to repeat the process. It can transport many sodium and potassium ions for each molecule of ATP hydrolyzed.
In summary, the sodium-potassium pump uses ATP as an energy source to actively transport three sodium ions out of the cell and two potassium ions into the cell, against their concentration gradients. This process is crucial for maintaining the appropriate balance of these ions, which is necessary for various cellular functions.