Re: What is the Sodium Potassium Pump

First off, I apologize that this response wasn't in time for your test.

The Sodium-Potassium pump is a transmembrane protein that moves sodium ions out of a cell while moving potassium ions in. Many types of cells require an electrical potential, or difference of charge, across the membrane in order to function. Nerve cells use this membrane potential to send electrical signals along nerves. Muscle cells maintain this potential to respond to elecrical signals coming from nerves and to contract when needed. For every two potassium ions that are pulled in from outside the cell, three sodium ions are moved from inside to outside the cell. All this occurs because the protein changes its shape. This change is initiated by adding a phosphate group to the inner side of the protein. The phosphate comes from ATP, so the pump requires energy.

ATP is used to power contraction of muscles. Relaxation is a passive process, just in the absence of a signal the muscle does not contract and therefore requires no energy. Generally, muscles are slightly contracted at all times. This is called muscle tone, and requires some ATP at all times.

Running out of ATP is tantamount to being dead, without energy the body cannot function. If ATP reserves are low, you might be lethargic or sleepy, but the body will do all it can to make ATP from something. Carbon-based (organic) molecules are held in reserve, mostly as fat, to meet energy needs when we are not eating (fasting). If those reserves are gone, the body will turn to any available organic molecules for metabolism. In extreme cases, such as severe anorexia, the body will metabolize proteins in its own tissues and basically digest its own muscles.