Chapter 2 - The Chemical Level of Organization - Checkpoint - Page 31: 3

Isotopes are two or more forms of an element with the same number of protons in their atomic nuclei but with different numbers of neutrons. For example, the two most common stable isotopes of Carbon are Carbon 12 and Carbon 13. Both Carbon 12 and Carbon 13 have six protons in their atomic nuclei , so they both have the atomic number 12( number of protons); however, Carbon 12 has 6 atomic neutrons while Carbon 13 has seven . This means that the atomic mass/weight (protons +neutrons) of C12 is 12 and that of C13 is 13. Free radicals Free radicals are chemical species --molecules, atoms, ions -- with an unpaired valence electron. Free radicals are very chemically reactive and may damage body tissue by reacting with cell membranes and DNA leading to cellular malfunction and in some cases development of cancerous growths.. Free radicals are often formed when oxygen reacts with certain molecules; therefore, injudicious exercise has the potential of enhancing the formation of free radicals in muscles.

Isotopes are forms of an element with different atomic mass/weight but with the same atomic number.. There are 15 isotopes of Carbon element all of which have 6 protons in their atomic nuclei. The three best known are Carbon 12( 6 neutrons), Carbon 13 ( 7 neutrons), and Carbon 14( 8 neutrons). Carbon 14 is radioactive with a long half-life of almost 6,000 years. A free radical is a group of atoms with an odd or unpaired electron in its outermost or valence shell. Free radicals are very reactive and may react with molecules in tissues --membranes, DNA etc with resulting tissue damage and cancer development. Oxygen is closely related to the formation of free radicals,and injudicious exercise may enhance free radical damage of muscle tissue . Other factors that may potentiate the development of free radicals are alcohol, pesticides, air pollution, industrial and household cleaners and fried foods. Some common free radical species are: Superoxides R-O-O ( unpaired electron on the first oxygen atom) Singlet oxygen O-O (unpaired electron on the first oxygen) Hydroxyl O-H (unpaired electron on first oxygen atom Nitric Oxide N=O(unpaired electron on the Nitrogen) Antioxidants that act to inactivate free radicals in the body include Vitamin A ( beta carotene), Vitamin C ( Ascorbic acid) and Vitamin E (alpha- tocopherol)