Mitochondrion
Mitochondrion is known as the power house of the cell. In respiration, the last steps of release of energy (from food) occur here.
There are three steps in respiration, glycolysis, kreb's (citric acid) cycle, and the electron transfer. Glycolysis occurs outside the mitochondrion. Kreb's cycle and electron transfer occur inside the mitochondrion.
So, the mitochondria are very important.
Structure of the mitochondrion
A mitochondrion is an organelle enclosed with 2 layers of membranes. The outer membrane gives shape to the structure.
The inner membrane is heavily folded to form cristae. The fluid filling the space is called matrix.
The matrix is full of substrates, intermediates, enzymes and co-enzymes required for the reactions in kreb's cycle.
Also, in the matrix there is some ribosome DNA. Mitochondrion has its own DNA. So, the inheritance of the mitochondrion is independent from the whole body. Its DNA is mainly inherited from the mother. It is because the DNA from the sperm would be metabolized away sooner after fertilization. (Ref : Scientific American, July, 2004 ,pp. 17)
On the cristae are numerous stalked granules. It is believed that they contain enzymes and co-enzymes required for electron transfer.
Therefore, electron transfer can occur rapidly.
At the last step of electron transfer, oxygen will accept electron and become water. Therefore, mitochondria are the destination of oxygen in breathing.
At the same time, water is produced. This water would move out of the mitochondria, expelled out of the cell and excreted out of body.
(26.09.2005)
