Final answer:
Ion gradients across the cell membrane establish concentration gradients and are essential for many physiological functions.
Step-by-step explanation:
The ion gradients across the membrane maintain concentration gradients and are also necessary for many physiological functions. These ion gradients are established by the movement of ions through ion channels in the cell membrane. Ion channels allow the formation of a concentration gradient between the extracellular fluid and the cytosol. This concentration gradient is important for various cellular processes.