Free radicals can be formed through the environment as well as through the natural human physiological processes. Free radicals are the result of stress, diet, smoking, exercise, alcohol, inflammation, drugs or even exposure to air pollutants and sunlight. Though there are many types of free radicals that can be formed, the most common in aerobic (oxygen breathing) organisms are oxygen free radical. These are also often referred to as Reactive Oxygen Species (ROS). They include hydroxyl anions, superoxides, hydrogen peroxide and singlet oxygen. In this post, we will learn what is a free radical and how are they formed.
What is a Free Radical?
A free radical can be defined as an atom or group of atoms that have an unpaired electron and hence are very unstable and highly reactive.
The chemical behaviour of an atom is determined by the number of electrons in its outermost shell. So, when the outermost shell is full, the atom is stable and has a tendency of not to engage in chemical reactions. However, when the outermost shell is not full, the atom is very unstable. It will attempt to stabilize itself by either losing or gaining an electron to either completely fill or empty its outermost shell. Else it will share its electrons by bonding with another atom which is also looking to complete its outer shell. It is quite common for an atom to complete its outer shell by sharing an electron with another atom simultaneously forming a bond.
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How Do Free Radicals Form?
Free radicals are formed when one of these weak bonds between the electrons is broken and an uneven number of electrons remain. This implies that the electron is unpaired, which make it chemically reactive. It will then try to steal an electron from a neighbouring molecule to stabilize itself.
Once a free radical is formed and it succeeds in gaining another electron from a nearby molecule, it leaves the victim short of an electron and hence has now made this new molecule a free radical. This free radical will, in turn, try and steal an electron as well. This results in a free radical cascade, and an enormous chain reaction of free radicals that rapidly wreaks havoc on living tissue. It is believed that the chain reaction can trigger 6.023 x 1021 billion molecules to react in a second!
Free radicals can be formed spontaneously or maybe they are the result of exposure to heat, light or something else in the environment. Many times the body’s immune system creates free radicals on purpose to neutralize bacteria and viruses.
In our human body, there are vast arrays of molecules that are more susceptible to free radical attacks than the others. These include DNA, RNA, fats, cellular membranes, vitamins, proteins and carbohydrates.
Quite unfortunately, oxygen is very susceptible to free radical formation. Now with aerobic organisms, this can be very dangerous. Oxygen-free radicals are also responsible for the overall ageing process and are responsible for cancer, photoaging and inflammation of the skin. Oxygen-free radicals lead to lipid peroxidation, which ultimately results in damage to cell membranes. This can cause skin cancer, premature ageing, and cell death.
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