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Free radicals

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Bashar Imran

on 25 December 2012

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Transcript of Free radicals

Free Radicals Bahsar Imran
Heba Zafer
wessam Matar Definition: Atoms or groups of atoms with an odd (unpaired) number of electrons and can be formed when oxygen interacts with certain molecules.

"Free radicals are usually unstable toward losing or picking an extra electron so that all electrons in atom will be paired"

Damage occurs when the free radical encounters another molecule and seeks to find another electron to pair its unpaired electron. The free radical often pulls an electron off a neighboring molecule, causing the affected molecule to become a free radical itself. The new free radical can then pull an electron off the next molecule, and a chemical chain reaction of radical production occurs.


"DNA cross-linking" Endogenous sources Exogenous sources 1- energy production process within the cells. 98% of the oxygen we breathe is used within our cells in the production of energy

2-the body immune system ( phagocytes & macrophages) these cells propsefully create them to neutralize viruses & bacteria.

3-normal metabolism of fat, carbohydrates and proteins.

4-Stress especially oxidative stress.

5-Low blood supply – generally occurs during heart attacks and strokes. 1- Environmental contaminants such as pollution. Cigarette smoke

2- prolong exposure to Ionizing , UV and Xray radiation.

3-Petroleum based products .

4-Unhealthy foods "processed foods, fried foods, barbecued and charbroiled foods" . Reactive oxygen species (ROS) Reactive nitrogen species (RNS) "Chemically reactive molecules containing oxygen. include oxygen ions and peroxides". * ROS formed by several different mechanism :

1-The interaction of ionizing radiation with biological molecules.
2-Byproduct of cellular respiration. (Mitochondria). cells of the thyroid gland must make hydrogen peroxide in order to attach iodine atoms to thyroglobulin in the synthesis of thyroxine. 2-Macrophages and neutrophils must generate ROS in order to kill some types of bacteria. Harmful effects Neutrophils kill off engulfed pathogens by using the enzyme catalyzes the reaction of hydrogen peroxide with chloride ions to produce the strongly antiseptic hypochlorite ion. Important of ROS 1- damage of DNA.
2- oxidations of polyunsaturated fatty acids in lipids (lipid peroxidation).
3- oxidations of amino acids in proteins.
4- oxidatively inactivate specific enzymes by oxidation of co-factors. Atomic oxygen has two unpaired electrons in separate orbits in its outer electron shell.  This electron structure makes oxygen susceptible to radical formation.  The sequential reduction of oxygen through the addition of electrons leads to the formation of a number of ROS including: superoxide , hydrogen peroxide, hydroxyl radical , hydroxyl ion ,and nitric oxide. * Reactive nitrogen species act together with reactive oxygen species (ROS) to damage cells, causing nitrosative stress. nitric oxide (·NO) with superoxide (O2·−) to form peroxynitrite (ONOO−) * ROS normally exist in all aerobic cells in balance with biochemical antioxidants.

*Oxidative stress occurs when this critical balance is disrupted because of excess ROS, antioxidants depletion, or both.


ROS can cause tissue damage by reacting with
lipids in cellular membranes, nucleotides in DNA ,sulphydryl groups in proteins and cross-linking/fragmentation of ribonucleoproteins . Antioxidants "A molecule that inhibits the oxidation of other molecules."

They terminate chain reactions by removing free radical intermediates, and inhibit other oxidation reactions. They do this by being oxidized themselves, so antioxidants are often reducing agents.

The function of antioxidant systems is NOT to remove oxidants entirely, but instead to keep them at an optimum level Antioxidant include : 1-Beta-carotene
2-Selenium
3-Vitamin A
4-Vitamin C
5-Vitamin E Beta-Carotene
It is the best quencher of singlet oxygen (an energized but uncharged form of oxygen that is toxic to cells). Beta-carotene is used for scavenging free radicals in low oxygen concentration Selenium
Is a trace element. It forms the active site of several antioxidant enzymes including glutathione peroxidase. Vitamin E

It is the major antioxidant in all cellular membranes, and it protects polyunsaturated fatty acids against oxidation. Because it is fat-soluble, it safeguards cell membranes from damage by free radicals. Vitamin C
It scavenges free radicals that are in an aqueous environment, such as inside the cells. It is believed to be the most important antioxidant in extracellular fluids ANTIOXIDANT-ENZYMES
Superoxide dismutase, catalase, and glutathione peroxidase serve as your primary line of defense in destroying free radicals. Therapeutic use of antioxidants for oral lesions The possible uses of antioxidants for oral mucosal lesions include the following:

1. Prevention of lesions in high-risk individuals with mucosa that clinically appears normal with no history of either premalignant or malignant lesion.



2. In patients who have had either premalignant or malignant oral lesions that have been successfully treated, in order to prevent recurrence of the treated initial lesion or to prevent the development of a second or a separate primary. TAKE HOME MESSAGE MEASUREMENT OF FREE RADICALS *Free Radicals have a very short half-life.
* Only react locally .
* Measure the products of oxidation that the free radicals have generated in the cell, oxidating lipids, proteins, amminoacids .

* The intensity of the colour is proportional to the quantity of free radicals present which turn into value that expressed in Carr Units

Norma values are below 250 U Carr . 1-Supplement your diet with antioxidants... Seven Essentials.

2- Eat natural food (fruit & vegetable ) and avoid fast food .

3-Drink pure, unchlorinated water (chlorine is an oxidant).

4- Breathe fresh, clean air & avoid cigarette smoking.

5- Follow a balanced training program that emphasizes regular exercise.

6-Avoid all use of dental metals (except titanium). THANK YOU 1-Chain breaking or scavenging.
vitamin E (tocopherol), vitamin C (ascorbic acid), vitamin A (carotene).

2-Preventative antioxidants.
Those substances containing thiol groups they are largely proteins by nature (eg albumin, transferrin, lactoferrin, caeruloplasmin, haptoglobin, and ascorbic acid).

3- Enzyme antioxidants Types of function
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