Answer
The two main factors responsible for the electrochemical gradient are the concentration gradient of solutes across the plasma membrane and the difference in electrical charges between the inner and outer surfaces of the plasma membrane. Concentration gradients of substances differ across the plasma membrane because of its selective permeability. The concentrations of sodium(Na+)and of oxygen(O2) are higher in the extracellular fluid, and the concentrations of potassium (K+) and of carbon dioxide (CO2) are higher in the cytosol. Substances tend to move down their concentration gradients; that is, they tend to move from an area of higher concentration to one of lower concentration. Regarding charge, the inner surface of the plasma membrane is more negatively charged and the outer surface is more positively charged. The difference in charge between the inner and outer surfaces is the electrical gradient, also known as the membrane potential because it obtains across the plasma membrane. The propensity of a given molecular species or ion to move into or out of a cell will be influenced by the combined effect of two forces: the concentration gradient of the solute moiety and the membrane potential. This combined effect of the concentration gradient and the membrane potential on a given molecule or ion is called the electrochemical gradient.
Work Step by Step
The electrochemical gradient is also affected by the nature and size of the charge on the solute molecule or ion.
