A chemical gradient occurs when more of one molecule is on one side of a membrane, and more of another molecule is on the opposing side. An electrical gradient occurs when more positive or negative ions are on either side of a cell membrane. The presence of an electrical gradient can result in a membrane potential, or voltage difference.
The combination of a chemical and electrical gradient can result in an electrochemical gradient that drives the movement of ions and molecules across a membrane.
An electrochemical membrane can have opposing component gradients.
The minimum voltage is observed as the resting potential of the cell membrane. This has a value of -70 millivolts and exists when there is no stimulus present. After a stimulus is applied, the sodium-potassium channels allow the movement of ions in and out of the cell membrane. Before the channel is able to close again and restore itself to the resting potential, hyperpolarization occurs and a maximum voltage of about 30-40 millivolts is achieved. <span />
Only differentiation creates more of the same types of cells. ... Only self-renewal creates more of the same types of cells. Only self-renewal depends on gene expression
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns
