WHAT ARE FREE RADICALS?
A free radical is defined as an atom, which has an unpaired electron - an electrically imbalanced atom. These are highly reactive and they always try to steel an electron from another molecule nearby by creating an imbalance of the molecules or cells.Redox Chain: (Reduction oxidation reaction chain): When a free radical steals an electron from a nearby molecule it makes the other molecule a free radical. This is called free radical chain or Redox Chain.
SOURCES OF FREE RADICALS:Human body is exposed to free radicals within the body (intrinsic) or from outside (Extrinsic).
INTRINSIC - SOURCES (INTERNAL)
1.Incomplete use of oxygen in the mitochondria.
2.Phagocytic cells releasing peroxides.
3.Interaction with cellular metals.
4.Oxidant enzymes - Cyclo-Oxyginase, MAO etc.
EXTRINSIC - SOURCES (EXTERNAL)
1.Air pollutants.
2.Cigarette smoke.
3.Ultra violet rays / sunlight.
4.Radiation.
5.Drugs.
6.Foods etc.
INTRINSIC:Free radicals are formed by incomplete aerobic metabolism in the mitochondria. These are called super oxide radicals.Metals like iron and copper can produce free radicals in the presence of ferrous metals & can react with super oxide radicals to form reactive radicals (OH2-).
Phagocytic cells:Macrophages and other phagocytic cells produce hydrogen peroxide to kill intracellular organisms and it also damages surrounding cells, common occurrence in inflammatory reactions.
Oxidant enzymes:The enzymes cyclo-oxygenase, monoamine oxidases etc, are essential for prostaglandin formation and degradation of catecholamines & during the process, free radicals are formed.
EXTRINSIC: Air pollution, cigarette smoke, ultra violet-radiation, sunlight, radiation, drugs and energy production.
Free radicals - Benefits:Free radicals are produced by WBCs in attacking pathogenic / foreign materials to protect the body. They destroy pathogens, but when produced in excess they damage tissues than protecting.
Harmful effects of free radicals:Free radicals are capable of extensive damage to all vital constituents of cells leading to cell death.
1. Cell membranes:Cell membranes are formed of lipids (poly unsaturated fatty acids) and are particularly vulnerable to free radical damage. The disruption of the cell membrane function leads to break down of receptors of the membrane and cell itself.
2. DNA:DNA is the most important part of cell. The free radical attack result in breaks in the DNA strand and can be responsible for cancer producing effects, mutation and cell death due to chromosomal damage.
Other effects are:
1.Damage of cellular membranes & organells.
2.Free radical damage of proteins leads to inactivation of enzymes.
3.Improper Carbohydrates metabolism results in improper energy release.
4.DNA damage leads to mutation, cancer, decreased protein synthesis.
DISEASE BY FREE RADICALS
Reperfusion Ischemia, Atherosclerosis, Ischemic Heart disease, Heart attack, Hypertension, DiabetesInflammation, Arthritis , Inflammatory bowel disease, Pancreatitis, Cancer, Neurological , Neuritis, StrokeParkinson's disease ,Trauma, Sepsis, Hypoxia, Ageing,Cancer ,Cataract, Pulmonary disease, lukemia etc.When there are more free radicals and less antioxidant, it leads to DNA damage of cells leading to improper instructions in cellular function. The increased free radicals damage immune system and causes cancer.
AGING:As a person ages, cells can be easily damaged by free radicals. This is because the anti oxidant in the body comes down and degenerative changes like diabetes, blood pressure, skin wrinkles, cataract, atherosclerosis etc take place.
ANTIOXIDANTS: are substances whose presence in relatively low concentrations significantly inhibits the destruction of target cells by free radicals. They neutralize free radicals before they can cause damage. Hence anti oxidant systems in the body and anti oxidants that we consume in food are important for protections of health.
ANTI OXIDANTS
Enzymatic & Non-enzymatic
Prevention of metal ions in free radicals formation.
Neutralizes or Scavenges or chain breaking type.
Anti oxidant Enzymes:These anti oxidant enzymes are intra cellular. They are,
1. Super Oxide Dismutase (SOD):It inactivates super oxide ions by converting it into hydrogen peroxide. SOD is high in tissues with high oxygen utilization like heart, liver, brain etc. There are two types of SOD enzymes:
1) Cytosolic- Copper - zinc dependent (in cells) & Manganese dependent - in mitochondria.
2. Catalases: This catalyses formation of water from hydrogen peroxide.
3. Glutathione peroxidases:Removes hydrogen peroxides and other oxidants. This is selenium dependent and is abundant in heart, lungs, brain & RBCs.
4.Scavenging or chain breaking antioxidants (Suicidal antioxidant)
These react with free radicals before they attack cells & these agents sacrifice themselves in saving the cells.
Eg. Ascorbic acid (Vit-C) Alpha Tochopherol (Vit.E), Betacarotein etc.It is also to be noted that antioxidants work as a team. Some antioxidants protect others. Eg. Flavonoids can protect Vit.C, which in turn regenerates Vit.E.
ANTI-OXIDANTS & FUNCTIONS:Antioxidants function to neutralize the free radicals and protect cell membranes, proteins, DNA and vital organs and prevent diseases and delays aging process and age related health loss. When there is an excess of free radicals and reduction of antioxidants then one can supplement with antioxidant nutritional supplementations and also include more of fresh fruits ( colored fruits) and vegetables which provide the natural antioxidants and prevent degenerative diseases from manifesting and retains healthy life longer and stronger.
The table below shows the free radicals and the antioxidants that inactivate the corresponding free radicals and the mode by which it does.
Free radical Antioxidants
Preventive & Scavenging.
Lipid peroxide -Glutathione Beta-carotene.
Hydrogen peroxide -Catalase Vit.E.
Superoxide -Super oxide Dismutase Vit.C.
Hydroxy radical- Vit.A / Vit.E
Akoxy radical - Betacarotene
Peroxy radical - L-glutamic acid.
Singlet oxygen -- L-Cysteine, Glycine, Selenium Copper,Manganese &Magnesium.
RKS Nair
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