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Outline of the Mitochondrion


Electricity and ATP

In human cells, the mitochondria are the structures where energy (ATP) is produced. In the biochemical literature ATP stands for Adenosine Tri Phosphate. When we talk about ATP, or energy production through ATP, we mean useful energy, i.e. energy which can be used by the organism for example for muscle contraction, transport purposes, etc. Heat, a form of physical energy too, is not covered by the term ATP. One can compare this with a mechanical motor: the motor produces both useful mechanical energy and heat, which can only be dissipated in the environment.

Electrical currents are essential in the energy production through ATP.
Mitochondria are a special type of organelles. The mitochondria have a double layer, composed of an outer and an inner membrane. It is interesting to note that a membrane is a double layer as well, so in fact the mitochondria have a double double layer. Please note that the DNA of the mitochondria differs from the DNA of the nucleus. As a matter of fact the DNA found in the nucleus of a cell is specific for the individual composed of those cells. On the other hand the DNA found in the mitochondria in a cell differs from the nuclear DNA found in that cell, yet is similar for humankind with some small racial differences. In the vegetable kingdom a similar situation holds for a type of organelles called the chloroplast, which also has its own DNA, different than the DNA of the nucleus of the cell of a plant.
We will first of all investigate what role electricity plays in the production of energy in the human cell.

Instead of looking at this process from a strictly chemical point of view, we will highlight the electrical side of this process. And we will see that electrical currents are essential for the production of the ATP energy. To start with, ATP production is closely related with electron transport. In current biochemical models, based on information obtained with advanced (electron)microscopes, in the human cell energy (ATP) is produced by the power of electron transport along the inner membrane of the mitochondrion, coupled with proton transport across the inner mitochondrial membrane. The following figures outline the ATP production process in the mitochondrion.