Oxidative stress

To understand oxidative stress, we review mitochondria together.MItochondriaMitochondria consume over 80 percent of the oxygen we breathe and make over 90 percent of the energy our cells need to function. They use the oxygen in the air we breathe to release energy from food. This process transforms food calories into chemical energy, water, and carbon dioxide. The released chemical energy is then stored in the form of adenosine triphosphate (ATP). ATP is the universal currency of energy used by all life on earth. It is like an electrical power source that drives the engines of the cell. This process...
Nội dung trích xuất từ tài liệu:
Oxidative stress Oxidative stressTo understand oxidative stress, we review mitochondria together.MItochondriaMitochondria consume over 80 percent of the oxygen we breathe and make over90 percent of the energy our cells need to function. They use the oxygen in the airwe breathe to release energy from food. This process transforms food calories intochemical energy, water, and carbon dioxide. The released chemical energy is thenstored in the form of adenosine triphosphate (ATP). ATP is the universal currencyof energy used by all life on earth. It is like an electrical power source that drivesthe engines of the cell. This process of burning food to make ATP is calledoxidative phosphorylation. Only mitochondria can do it. Mitochondria areimportant in relation to the aging process for two reasons: their role in energyproduction and, the generation of free radicals. In a healthy state, about 20% of theoxygen we breathe forms free radicals. In an unhealthy state up to 80% of theoxygen we breath forms free radicals.Oxidative stressOxidative stress represents an imbalance between the production andmanifestation of reactive oxygen species and a biological systems ability toreadily detoxify the reactive intermediates or to repair the resulting damage.Disturbances in the normal redox state of tissues can cause toxic effects throughthe production of peroxides and free radicals that damage all components of thecell, including proteins, lipids, and DNA. Some reactive oxidative species caneven act as messengers through a phenomenon called redox signalingFree radicals:Free radicals are lacking one electron. Having an unpaired electron makes theseradicals very unstable, then the radicals will start attacking healthy cells to findone.They take that electron from another molecule, stabilizing themselves, and indoing so, create a new free radical. This new unstable molecule starts the searchall over again for another cell to get an electron from.A chain reaction develops causing repeated damage to healthy cells, first attackingthe cell membrane and then working its way through to the DNA of the cell. Thisis the beginning of disease processes which debilitate our bodies with degenerativeconditions, inflamed tissues, compromised immune systems and cancer, just toname a few.Generally, free radicals react with other molecules, damaging them. Howeversome processes such as the killing of bacteria by neutrophil granulocytes isbeneficial.Causes of oxidative stress:Common sources of oxidative stress are: toxicity, chr onic inflammation, glycation,stress, excessive exercise, some medications, alcohol, cigarette smoke, and dietaryfactors such as consumption of refined carbohydrates (white sugar and flour, for astart), bad fat, bad oils, fried oils, and foods cooked at high temperature (fried orbarbequed for example). Overeating may be another source of oxidative stress.The more food that is burned within the mitochondria the more free radicals areproduced.Oxidative and disease:The effects of oxidative stress depend upon the size of these changes, with a cellbeing able to overcome small perturbations and regain its original state. However,more severe oxidative stress can cause cell death and even moderate oxidation cantrigger apoptosis, while more intense stresses may cause necrosis.Oxidative stress contributes to tissue injury following irradiation and hyperoxia. Itis suspected (though not proven) to be important in neurodegenerative diseasesincluding Lou Gehrigs disease (aka MND or ALS), Parkinsons disease,Alzheimers disease, and Huntingtons disease. Oxidative stress is thought to belinked to certain cardiovascular disease, since oxidation of LDL in the vascularendothelium is a precursor to plaque formation. Oxidative stress also plays a rolein the ischemic cascade due to oxygen reperfusion injury following hypoxia. Thiscascade includes both strokes and heart attacks. Oxidative stress has also beenimplicated in chronic fatigue syndrome.