In biochemistry, series of chemical reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions ordinarily impossible in conditions within a cell are performed. Different chemical reactions are used in combination in chemical synthesis in order to get a desired product. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. The substance or substances initially involved in a chemical reaction are called reactants. These processes are called chemical reactions. Extraction from C-1´ or C´-2 leads to alkali-labile bonds, which differ from the AP (apurinic or apyrimidinic) site formed by the depurination of DNA.A chemical reaction is a process that always results in the interconversion of chemical substances. All around us, even inside us, all kinds of chemicals are coming together and changing into new substances. ![]() The second way matter can change is through a chemical reaction. H atom extraction from the 3'-C leads to unknown products. However, not all physical reactions are easily reversed. ![]() Extraction of an H atom from the 4´-C or the 5´-C of the sugar, then addition of O 2, leads to strand breaks. To better understand the difference between chemical vs. In oxygenated solution, oxygen reacts rapidly and irreversibly with each of the carbon radicals so formed. In a physical change, no new substance is made, like when water turns to ice. H atoms attached to each of the five carbon atoms can be extracted by OH. OH radicals are the only reactive species in oxygenated solutions that react with any efficiency with the sugar. For DNA in dilute aqueous solution, the effects of irradiation are caused by the products formed by the action of ionizing radiations on water: the OH radical, the hydrated electron, the H atom, H 2O 2, and H 2. By indirect action, the effects of reactive species are formed in the surroundings that diffuse to the target molecule and react with it. ![]() By direct action, the effects of energy are deposited directly in the target molecule. A chemical transition, also known as a chemical reaction, is a process that transforms one or more substances into one or more new and different substances. Usually, radiation effects on particular molecules, such as DNA, are ascribed to the sum of two processes: direct action and indirect action. The radiations whose effects are covered in the chapter-X rays, γ rays, and high energy electrons-interact with matter by transferring energy to the electrons in the irradiated sample. It focuses on the effects produced by irradiation in the presence of oxygen. These changes are permanent and cannot be reversed. Such changes are called chemical changes. This chapter discusses the effects of ionizing radiation on DNA. So what is a Chemical Change The type of change in which one substance reacts with another to undergo a change in its chemical composition, thus resulting in the formation of new substances.
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