Final answer:
The unequal distribution of ions across the plasma membrane is reflected by the electrochemical driving force, which includes both a chemical and an electrical component.
Step-by-step explanation:
The reflection of the unequal distribution of positive and negative ions across the plasma membrane is described by the electrochemical driving force. This force consists of two components: the chemical driving force, which is related to the ions' concentration gradient, and the electrical driving force, which is the effect of the membrane potential on the ions' movement.
The inside of the cell is negative compared to the outside, favoring the movement of positive ions (cations) into the cell and negative ions (anions) out. The membrane potential is crucial for this process, as it contributes to the voltage across the membrane which is important for the conduction of electrical impulses in nerve cells.
The electrochemical gradient is the combined effect of the concentration gradient and the electrical charge, which significantly influences the function of muscle and nerve cells.