What does the term "membrane potential" refer to?

• A. The overall charge of the cytoplasm
• B. The difference in charge distribution across the cell membrane
• C. The potential energy stored in ion gradients
• D. The activity of ion channels in action potentials

Answer: (B)

The term "membrane potential" refers specifically to the difference in charge distribution across the cell membrane. This difference in charge arises due to the varying concentrations of ions on either side of the membrane, primarily sodium (Na+), potassium (K+), chloride (Cl-), and calcium (Ca2+). The membrane potential is measured in millivolts (mV) and is typically negative in resting cells, meaning the interior of the cell is more negatively charged relative to the exterior.

This electrochemical gradient is crucial for many cellular processes, including the generation and propagation of action potentials in excitable cells like neurons and muscle cells. The membrane potential is dynamic and can change in response to stimuli, reflecting the movement of ions across the membrane through various channels and transporters. Understanding membrane potential is fundamental to topics such as signal transduction, intercellular communication, and overall cellular homeostasis.