Final answer:
The sodium-potassium pump's 3 to 2 ratio of Na+ to K+ maintains the electrochemical gradient and membrane potential by moving three Na+ out and two K+ in per cycle, utilizing ATP for transport. This stoichiometry of ion transport ensures efficient use of cellular energy.
Step-by-step explanation:
The sodium-potassium pump has a 3 to 2 ratio because it moves three sodium ions (Na+) out of the cell and two potassium ions (K+) into the cell during each cycle to maintain the electrochemical gradient critical for cellular functions. This ratio contributes to the net export of one positive charge per cycle, which helps establish a negative membrane potential essential for processes such as nerve impulse transmission and muscle contraction. The pump utilizes ATP to transport these ions against their concentration gradients, a mechanism that is energy-intensive. It requires phosphorylation, which involves a phosphate group from the ATP molecule binding to the pump protein, causing it to change shape. This shape change is necessary for the movement of ions across the membrane. The 3 to 2 ratio, therefore, is linked to the stoichiometry of ion transport (Option A), ensuring that the cellular energy is used efficiently to maintain the required concentrations of Na+ and K+ ions for cellular health and function.