Oxygen Radical
PKGhatak, MD
The radicals are molecules containing an unpaired electron, and that makes them very reactive. Free radicals are highly reactive and unstable molecules containing unpaired electron., Radicals can damage the RNA and DNA and eventually can kill a cell.
Oxygen.
In the air, the oxygen is present in three different forms -
1. Oxygen molecule( O2,)
2. Oxygen atom( O1)
3. Ozone (O3).
Oxygen is a primary reactant, and the reaction gives out heat and it is called exothermic.
Mitochondria are the main metabolic center of the cells; the more active the cell is, the greater the chance of generating radicals. The next order of cellular active sites is the endoplasmic reticulum, the cytosol, and the cell membrane.
Source of Oxygen Radical:
Radicals are generated: Two sources - cellular and extracellular. The Non-cellular. Air pollution, cigarette smoke, alcohol, Ozone, heavy metals, radiation, drugs, industrial solvents, pesticides, and herbicides are the main sources.
Oxygen Radicals and Non-Radical Oxidants.
|
Radical |
Symbol |
Oxidants |
Symbol |
|
Superoxide |
O*- |
Hydrogen peroxide |
H2O2 |
|
Hydroxyl |
*OH |
Single Oxygen |
1O2 |
|
Peroxyl |
R00* |
Ozone |
O3 |
|
|
|
Organic peroxide |
ROOH |
|
|
|
Hypocaloric acid |
HOCl |
|
|
|
Hypo bromic acid |
HOBm |
Nitrogenous Radicals and Oxidants.
|
Radical |
Symbol |
Oxidants |
Symbol |
|
Nitric acid |
NO* |
Peroxyl nitrogen |
ONOO |
|
Nitrogen dioxide |
NO*2 |
Nitrosyl anions |
NO |
|
|
|
Dinitro tetraoxide |
N2O4 |
|
|
|
Peroxyl nitrous acid |
OHOOH |
|
|
|
Nitryl chloride |
NO2Cl |
|
|
|
|
|
The body's defense against radicals:
Mechanism of countermeasures against radical :
1.Superoxide dismutases (SOD) remove O2 by greatly accelerating its conversion to H2O2.
2. Catalases in peroxisomes convert H2O2 into water and O2 and help to dispose of H2O2 generated by the action of the oxidase enzymes that are located in these organelles.
3. Other important H2O2-removing enzymes in human cells are the glutathione peroxidases.
The human body employs Enzymes and Non-Enzymes to neutralize free radicals and oxidants.
A list of enzymes act as antiradicals and antioxidants - Superoxide dismutase, Catalase, Glutathione peroxidase, and Glutathione reductase.
The Non-enzyme antioxidants are Vitamin E, Vitamin C, Carotenoids, Trace metals Selenium and Zinc, Flavonoids, Omega 3 and Omega 6 fatty acids, L-arginine, Coenzyme Q10, and Melatonin.
Diseases caused by radicals in humans:
Age-related conditions-
Loss of skin elasticity, wrinkles, cataracts, graying hair, and loss of hair.
Neurodegenerative diseases-
Parkinson's disease and Huntington's disease.
Autoimmune diseases-
Rheumatoid arthritis and various cancers.
Cardiovascular -
Coronary artery diseases.
edited May 2025
