The Mitochondria

What is a mitochondrion and what significance does it hold for the basis of molecular biology? To put it simply, a mitochondrion is and organelle commonly found in large numbers in the majority of cells. The Mitochondrion is responsible for biochemical processes such as, respiration, oxidative phosphorylation and ATP synthesis. Thus, the Mitochondrion, or mitochondria accountable, are known as ‘ATP factories’ or ‘the powerhouse’ of the cell.

It is obvious as to why mitochondria were studied in such detail. Richard Altmann first discovered and named them ‘bioblasts’ in 1890, however, 8 years later, a microbiologist, Carl Benda, termed them as what we now know them to be, ‘Mitochondria’. Mitochondria are one of the major ancient endomembrane

It is believed that an endosymbiotic event occurred where an organism capable of oxidative phosphorylation was consumed by another cell. This theory is backed up by the DNA, double membrane and mitochondrial specific transcription and translation mechanisms used to allow such a phenomenon to occur. Mitochondria still secure their characteristic double membrane structure and are still the primary source of ATP production, from their ancestors. Yet, their overall form has been altered, they have acquired innumerable new functions within the cell.

The current known structure of Mitochondria is that they are oval in shape and around the same size as a bacterium. George Palade and Fritijof Sjostrand studied mitochondria under the electron microscope. They discovered that mitochondria work on a two membrane system: an inner and an outer membrane. The inner membrane is highly folded and the ridges formed are known as cristae. Thus, the mitochondrion has two major compartments, the intermembrane space between the outer and inner membranes, and the mitochondrial matrix, bounded by the inner membrane. The matrix is the epicentre of reactions for the

A balanced relationship between fission and fusion is crucial as it determines mitochondrial structure. In some cell types, mitochondria can be separated in the cell and alter to form one interconnected membranous assembly. Within fusion, two mitochondria join together to from one single, bugger mitochondrion. Conversely, fission is when a single mitochondrion divides to give two mitochondria. Fusion and Fission are both mediated by dynamin-related GTPases. Fusion is mediated by mitofusin 1 and mitofusin 2 on the outer mitochondrial membrane and by optic atrophy 1 on the inner membrane. While fission is mediated by dynamin related protein 1. Interestingly, neuromuscular disease in humans is observed when there are mutations of the mediator proteins. If mitochondrial fusion is blocked, purkinje neurons, responsible for motor coordination, degenerate in the cerebellum defaulting in defect in the electron transport chain and in mtDNA. This suggests that ample equilibrium between fusion and fission is essential for sustaining the health of the mitochondrial