How is the electrochemical force defined?

• A. Pressure against osmosis
• B. The sum of chemical driving force and electrical driving force
• C. Movement of ions in one direction only
• D. The effect of solute concentration on cell tonicity

Answer: (B)

The electrochemical force is accurately defined as the sum of the chemical driving force and the electrical driving force. This concept primarily pertains to the movement of ions across a membrane and is crucial in understanding physiological processes such as neuronal signaling and muscle contraction.

The chemical driving force refers to the concentration gradient of ions—ions tend to move from areas of high concentration to areas of low concentration. The electrical driving force involves the effect of the membrane potential on ion movement; ions will move towards areas of opposite charge. When the two forces are combined, they produce the electrochemical gradient that dictates the direction and magnitude of ion flow across cell membranes.

Therefore, option B encompasses the critical aspects of both chemical and electrical influences that together form the electrochemical force, making it the correct answer. This understanding is essential in physiology since many cellular functions and signaling mechanisms rely on the movement of ions in response to these driving forces.