<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A type of unstable molecule that is made during normal cell metabolism (chemical changes that take place in a cell). Free radicals can build up in cells and cause damage to other molecules, such as DNA, lipids, and proteins. This damage may increase the risk of cancer and other diseases.</n0:def-definition><n0:def-source>NCI-GLOSS</n0:def-source></n0:ComplexDefinition>
<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>Molecules or atoms with at least one unpaired or 'free' electron in the outermost electron shell. Chemically unstable, free radicals stabilize themselves by appropriating an electron from a nearby molecule, thereby damaging that molecule by altering the electron number in its outermost electron shell. By-products of both normal cell processes and environmental toxin exposure, oxygen free-radicals in high concentrations may damage DNA, proteins, and lipids, thereby increasing the risk for various diseases including cancer. (NCI04)</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>