Which type of membrane transport do cardiac glycosides primarily affect?

Which type of membrane transport do cardiac glycosides primarily affect?

• A. Simple diffusion
• B. Facilitated diffusion
• C. Primary active transport
• D. Passive transport

Answer: (C)

Cardiac glycosides primarily affect primary active transport mechanisms in cells, particularly the Na+/K+ ATPase pump. This pump is responsible for maintaining the concentration gradients of sodium and potassium ions across the plasma membrane of cardiac cells. Cardiac glycosides, such as digoxin, inhibit this pump, leading to increased intracellular sodium levels. The elevated sodium concentration indirectly affects calcium levels through the sodium-calcium exchanger, ultimately enhancing cardiac contractility (a phenomenon known as positive inotropy). Understanding that the Na+/K+ ATPase is a crucial example of primary active transport is key here, as it requires ATP to move ions against their concentration gradients. This action is distinct from simple diffusion, which does not require energy, and facilitated diffusion, which involves transport proteins but still operates along the gradient without energy input. Passive transport also refers to movement that occurs without energy input, which is not the case with the mechanism influenced by cardiac glycosides.

Cardiac glycosides primarily affect primary active transport mechanisms in cells, particularly the Na+/K+ ATPase pump. This pump is responsible for maintaining the concentration gradients of sodium and potassium ions across the plasma membrane of cardiac cells. Cardiac glycosides, such as digoxin, inhibit this pump, leading to increased intracellular sodium levels. The elevated sodium concentration indirectly affects calcium levels through the sodium-calcium exchanger, ultimately enhancing cardiac contractility (a phenomenon known as positive inotropy).

Understanding that the Na+/K+ ATPase is a crucial example of primary active transport is key here, as it requires ATP to move ions against their concentration gradients. This action is distinct from simple diffusion, which does not require energy, and facilitated diffusion, which involves transport proteins but still operates along the gradient without energy input. Passive transport also refers to movement that occurs without energy input, which is not the case with the mechanism influenced by cardiac glycosides.