Mitochondria are the power houses of the cell.
These are the cell organelles inside which the energy is produced.
Mitochondria have the ability to self replicate without cell involvement.
This is due to presence of single strand of DNA in them.
This self replication is necessary inside the cell as they play a key role in cell metabolism. When they get worn out due to high activity, they are digested and new ones are produced in their place to keep the physiology.
Energy production: Glucose + O2 ———> ATP + H2O + CO2.
O2 in the reaction splits into (o) i.e. oxygen atom which is very oxidative to cell organelles, so it has to convert to other forms to be less destructive.
These mitochondria are a part of frequent analysis and also their tests indicate many prominent disorders.
Hence mitochondrial tests are done
1. For anti-oxidant study: Mitochondria during energy production also produce oxidizing substance. So mitochondria are the key sites of oxidative radicals. analysed for oxidation status, anti-oxidant enzymes located inside them. So mitochondrial test for oxidative radical species and also anti-oxidant enzymes is done.
For example malondialdehyde (MDA) which is formed by lipid peroxidase during oxidative stress is estimated as an indication of oxidative radical. The more MDA the more is oxidative stress and vice-verse.
Other anti-oxdiant enzymes are catalase and super oxide desmutase (SOD).
SOD breaks down OH- radical to form H2O2. Catalase breaks 2. H2O2 ———-> H2O + O2.
Lack of these enzymes is so dangerous as OH- & H2O2 accumulates in cells leading to damage.
2: For energy production study: Since mitochondria are energy houses of the cell. Any failure of energy indicates mitochondrial dysfunction. So mitochondria are analysed for the status of energy production.i.e. if the mitochondria are viable or not. If they are viable, it means they produce energy. This is done by checking the function of complex enzymes and also the membrane potential of mitochondria.
Of the complex enzymes ATP synthetase is the key as it is the enzyme in the end of cycle for ATP formation.
Other complex enzymes like SDH is also routinely analysed.
3: For cell death signal: Mitochondria on rupture, release Calcium and apoptotic factor which trigger apoptosis (i.e. slow cell death) for the cell to be destroyed. For this BACL proteins, membrane potential are analysed. Membrane potential indicates if membrane is damaged. BACL proteins indicate their leakage from mitochondria into cell.
In forensic studies: When a person is killed by poisons like cyanide sort, the mitochondrial complex enzymes are blocked resulting in obstruction of energy supply and the cell death and organ failure.