What type of transport creates and maintains the electrochemical gradient across a cell membrane?
a. Voltage gated ion channels
b. Mechanically gated ion channels
c. Sodium-Potassium pump
d. Aquaporins
The correct answer and explanation is:
The correct answer is c. Sodium-Potassium pump.
The sodium-potassium pump (Na+/K+ ATPase) is responsible for creating and maintaining the electrochemical gradient across a cell membrane. This pump is an active transport mechanism that moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, against their respective concentration gradients. The process requires energy in the form of ATP because it works against the natural tendency of molecules to diffuse from areas of high concentration to low concentration (passive transport).
For every three sodium ions pumped out of the cell, two potassium ions are pumped into the cell. This results in a higher concentration of sodium outside the cell and a higher concentration of potassium inside the cell. This unequal distribution of ions creates both a concentration gradient and an electrical gradient. The concentration gradient refers to the difference in ion concentrations between the inside and outside of the cell, while the electrical gradient is the difference in charge, as the pump moves more positively charged sodium ions out of the cell than potassium ions in.
This electrochemical gradient is critical for several cellular processes, including the generation of action potentials in neurons and muscle cells, nutrient uptake, and waste removal. Without the sodium-potassium pump, cells would not be able to maintain proper ion balance, leading to a disruption in cellular function.
Other options, such as voltage-gated ion channels and aquaporins, play roles in the movement of ions or water but do not actively create or maintain the electrochemical gradient. Similarly, mechanically gated ion channels are involved in the response to mechanical stimuli but are not responsible for maintaining the gradient. The sodium-potassium pump is the primary mechanism for maintaining the cell’s resting membrane potential and overall homeostasis.