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Paper Topic:

ROS and Aging

`Aging ' is defined as regular biological degeneration of cells and tissues with time . It occurs normally after sexual maturity , and continues , until death . Aging is a natural , irreversible process , and slows down cell division and replacement of old and worn out cells and tissues [7] . Genetics is one definite factor that controls human aging but beyond that , we have learnt that nutrition and diet , and environmental factors play a very important role and may promote or delay senescence [1] . For many years now , scientists and researches have put forward different theories to

support and explain the phenomenon of aging [1] . The most popular and widely accepted is the `Free-radical Theory of Aging [1] ' We also come across factors like reactive oxygen species , and antioxidants when we study about this theory [1] . It proposes that `oxidative damage ' induced by free radicals is the major under lying factor behind aging , meaning , oxidation of cells causes aging , or more crudely put , rusting of cells , causes aging

The nucleus of every atom is surrounded by a cloud of electrons [1] These electrons exist in pairs , in each orbital , with opposite spins [5] . If one electron spins clockwise , the other spins anticlockwise . The paired electrons keep the atom fairly stable , that is , in a state of lower energy [5] . If , for some internal or external reason one electron of a pair is removed , the atom is then called a `free radical [5] ' It becomes unpaired with respect to the spin of the lone electron , and enters a state of higher energy , which is relatively unstable [5] . Free radicals are very reactive , and are believed to be one of the major factors behind aging [5]

Many molecules in the cell are sensitive , and can be destroyed easily by free radicals . This is why it is believed that free radicals are behind a number of diseases like strokes , cardio-vascular problems and diabetes

Free radicals bring about `oxidation ' damage [2] . Oxidation does not necessary require the involvement of oxygen , as it implies [2] . It is defined on the basis of loss of electrons [2] . Free radicals pull an electron from any convenient molecule . The oxygen radicals are the most common free radicals found in biological pathways . Most other free radicals have oxygen as the central atom [2] . These are called `Reactive Oxygen Species [2] ' They are formed mostly in the mitochondria of cells . Our bodies are exposed to free oxygen radicals not only through environmental conditions like excessive sunlight and pollution , but these ROS are also generated endogenously [6] . They are also produced in diabetics . Other free radicals include superoxide , hydroxyl radical protein radical and nitrogen dioxide [6]

Since chemical cohesive bonds involve multiple atoms sharing electrons to form a molecule , the unwilling loss of electrons destroys chemical bonds . Taken from proteins , electron loss can cause protein cross linking , a key feature of stiffening tissues , disable hormones and enzymes , and damage cell structures . Taken from DNA , genetic defects can occur , which can cause defective compounds to be metabolized...

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