Electrons fill orbitals and shells in a very organized manner. They begin by filling orbitals in the shell closest to the nucleus. When that shell is full, they go into the next shell until that shell is full, and so on. Depending on the element, the outermost shell may or may not get completely filled with electrons. And the electrons may or may not be paired up in the orbitals in the outermost shell if that shell is not full. It’s these unpaired electrons in the outermost shell that make an atom unstable and highly reactive.
Free radicals are atoms or molecules that have a single, unpaired electron in their outermost shell. Free radicals are very unstable and react with other molecules by attacking those molecules and grabbing an electron. This leaves the attacked molecule with an unpaired electron, turning it into free radical that reacts with another molecule, thus starting a chain reaction. If the process gets out of control, it results in disruption of living cells. When free radicals react with other molecules, the reaction changes the structure and function of those molecules. On a cellular level, changes can lead to cell damage, dysfunction, and finally cell death.
Free radicals react with molecules inside our cells such as DNA, proteins, and fatty acids. DNA is our genetic material. Proteins do most of the work in our cells, and are required for the structure, function, and regulation of our body’s tissues and organs. Fatty acids are required for development and formation of healthy cell membranes, development and function of the brain and central nervous system, and for function and regulation of tissues, organs, and immune system. Reactions caused by free radicals speed up the aging process and are linked to many cancers and other degenerative diseases.
Antioxidants serve as scavenger molecules that neutralize free radicals by donating one of their own electrons to pair up with the unpaired electron in the free radical. The free radical becomes stabilized, making it non-reactive, and the cascade of reactions from the free radical is halted. The antioxidants remain stable after donating the electron, so no further reactions take place.
Free radicals are produced as part of our normal cellular function, signalling cell death (apoptosis), Free radicals are also introduced by stress, poor diet, inflammation, and exposure to the sun's ultra violet radiation, environmental pollutants, and cigarette smoke. Problems occur when there is an imbalance between free radicals and antioxidants, either because we have excess free radicals, not enough antioxidants, or both.
You can protect yourself by eating lots and lots of colorful fruits and vegetables, and by eating beans and legumes, which are all loaded with powerful antioxidants as well as by limiting your exposure to pollutants, cigarette smoke, and direct sun.