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Electrochemical Gradient

The cell membrane functions as a barrier. Keeping some molecules and ions trapped within a cell while keeping others out. One feature of this division of resources inside and outside of the cell is the maintenance of an electrochemical gradient. Ions that are critical for cell function including sodium and potassium are unable to diffuse across the membrane relying instead on movement by channels and transporters. Under normal conditions there is generally more sodium on the outside of a cell than inside. This creates a chemical or concentration gradient where sodium would flow across the cell membrane from outside to inside if it were given a path. Conversely, there is a lower concentration of potassium outside of the cell and more potassium inside. So its chemical gradient is in opposition to sodium's gradient. However, ion concentration is not the only factor creating a gradient across the cell membrane. The separation of ions and molecules with positive and negative charges also means that there is an electrical gradient present. The prevalence of positively charged sodium ions outside of the cell and the abundance of negative charged proteins inside are two major factors that contribute to the overall difference in charge across the membrane. Active transport uses energy to maintain the electrochemical gradient across the cell membrane with specialized membrane proteins moving ions against their electrochemical gradients. Under specific conditions however, the ions are allowed to move with their gradients. Generating energy for processes like glucose transport and providing a means for specialized cells such as cardiac, muscle and neurons to generate electrical impulses.