The o-quinones, themselves, are colorless, however they react with other phenolic compounds and can self-polymerize to form compounds which produce the brown color associated with apple oxidation (Nicolas et al.). This oxidation process forms a thin brown layer on the exposed surface of the apple. The rate of browning in different apple types is dependent on both the concentration of polyphenol oxidase and polyphenols within the apple (Nicolas et al.).

al., 1993; Forman & Dickinson, 2003). Though nitric oxide is not involved in as many individual processes as hydrogen peroxide, or at least a lower number of processes have been identified in current research, its presence in too great an abundance can disrupt proper signaling and trigger alternative signaling pathways other than those normally utilized in redox signaling (Forman & Dickinson, 2003). These redox signaling pathways have the potential

Chemical reactions occur when atoms, molecules, and ions interact with one other to form new substances. Chemical bonds are broken and new bonds are formed. Chemical bonds between atoms follow rules based on patterns of electron distribution within the involved atoms. When reactions take place, energy exchange occurs. When chemical bonds are broken, energy is released. When new bonds are formed, energy is stored. There are many types of chemical reactions.

It was used by Michael Faraday in the 1800s in his experiments on electromagnetism. Other inventors improved on the battery's original design and these improvements produced telegraphs and doorbells. Napoleon Bonaparte was so impressed with the invention that he recommended honors for Volta, including making him a count in 1810 (CIRL, Rubin, Scratch, Corrosion Doctors). From this first and crude battery evolved electrochemistry, electromagnetism, and modern applications of electricity (CIRL,

The energy it stores (?180 Wh kg?1) at an average voltage of 3.8 V is only a factor of 5 higher than that stored by the much older lead -- acid batteries. This may seem poor in the light of Moore's law in electronics (according to which memory capacity doubles every 18 months), but it still took a revolution in materials science to achieve it. Billions of lithium-ion cells

Physical Science Elemental Isotopes and Allotropes The 19th century discovery of the periodic table of the elements by Dmitri Mendeleev gave an organizing principle to understanding the structure of the atom, and deriving atomic weight. On the periodic table, the lighter elements have atomic weights which correspond to whole numbers. Hydrogen has an atomic weight of 1, which corresponds to the idea that it has only one proton (and the weight of