Free Radicals in the Body

Study Notes

A free radical is a molecular species with an unpaired electron in its atomic orbital that can exist independently.
Free radicals share common properties due to the unpaired electron.
They are highly reactive, posing a threat to macromolecules such as DNA, RNA, proteins, and fatty acids.

Energy released from breaking bonds is used to form molecules of ATP.
Electrons are extracted from glucose in a stepwise manner and transferred to other molecules.
Occasionally, electrons "escape" and are transferred to an oxygen molecule, forming superoxide.
Superoxide is a molecule with two atoms and one unpaired electron, also known as a reactive oxygen species.

The unpaired electron in free radicals destabilizes them, making them highly reactive.
Other reactive oxygen species include hydrogen peroxide and the hydroxyl radical.
Free radicals can cause chain reactions that ultimately damage cells.

Free radical reactions can continue unchecked unless stopped by a defense mechanism.
Chain reactions can change the permeability and fluidity of cell membranes, decrease protein activity, and alter receptor protein structure.

The body creates free radicals through normal metabolic processes.
Environmental sources such as excessive sunlight, ozone, smoke, heavy metals, ionizing radiation, asbestos, and other toxic chemicals can increase the amount of free radicals in the body.
These environmental sources can contribute to disease by overwhelming the free radical detoxifying systems and repair processes.

Oxidative stress refers to an imbalance between the amount of free radicals and the capabilities of the detoxifying and repair systems.
Sustained oxidative damage results only under conditions of oxidative stress.
Oxidative stress has been implicated as a contributing factor to various diseases, including cancer, atherosclerosis, arthritis, diabetes, kidney disease, Alzheimer's disease, Parkinson's disease, schizophrenia, bipolar disorder, emphysema, and cataracts.

Aging is a process that is genetically determined but modulated by environmental factors.
Tissue function declines with age, and oxidative stress is thought to contribute to this decline.
Recent scientific evidence suggests that oxidative stress is not the initial trigger for age-related decline of tissues, but rather a consequence of progressive dysfunction of metabolic processes.