36. Which of the following statements about Na+ -K + ATPase is correct?
1. It is responsible for generating the resting membrane potential
2. It transports Na+ and K+ ions down their respective gradients
3. It is responsible for generating an action potential
4. It indirectly regulates the volume of the cell
The Crucial Role of Na+ – K+ ATPase in Cellular Processes
The Na+ – K+ ATPase, also known as the sodium-potassium pump, is an essential membrane protein that plays a pivotal role in maintaining the proper functioning of cells. This enzyme is responsible for transporting sodium (Na+) and potassium (K+) ions across the plasma membrane, which is vital for various cellular functions. Let’s delve deeper into its roles and correct functioning.
Understanding Na+ – K+ ATPase:
The Na+ – K+ ATPase actively transports three sodium ions (Na+) out of the cell and two potassium ions (K+) into the cell, both against their respective concentration gradients. This process requires energy, which is provided by the hydrolysis of ATP, hence the name ATPase. The pump is vital for maintaining ion gradients, which are necessary for several critical physiological functions.
Key Functions of Na+ – K+ ATPase:
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Resting Membrane Potential Generation: One of the primary roles of Na+ – K+ ATPase is to establish and maintain the resting membrane potential. The difference in ion concentrations across the cell membrane (more sodium outside and more potassium inside) generates a negative charge on the inside of the cell relative to the outside. This negative charge is crucial for the proper functioning of excitable cells like neurons and muscle cells. The resting membrane potential is vital for the cell’s ability to respond to stimuli.
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Ion Transport Against Gradients: Na+ – K+ ATPase actively transports Na+ and K+ against their concentration gradients, which is an energy-intensive process. This ion transport helps in maintaining the proper ionic balance required for cellular processes. Without this pump, cells would not be able to maintain the necessary internal and external ion concentrations to support normal functions.
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Regulation of Cell Volume: The pump also plays a critical role in regulating cell volume. By actively transporting sodium out of the cell, it helps to prevent excess sodium from accumulating within the cell. This prevents excessive water influx and subsequent cell swelling, which could otherwise lead to cell lysis. In this way, the Na+ – K+ ATPase helps to maintain osmotic balance and proper cell volume.
The Correct Statement about Na+ – K+ ATPase:
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Answer: 4. It indirectly regulates the volume of the cell.
While the Na+ – K+ ATPase does not directly cause an action potential or transport ions down their gradients, it plays a significant role in regulating cell volume and contributing to the maintenance of the resting membrane potential.
Summary:
The Na+ – K+ ATPase is essential for maintaining cellular homeostasis, generating the resting membrane potential, and regulating the volume of the cell. By actively transporting sodium and potassium ions across the plasma membrane, it ensures the proper ionic balance necessary for a variety of cellular functions. This ATP-dependent pump is central to the functionality of neurons, muscle cells, and other excitable cells.
