Cell damage Clause Samples

Cell damage. Radiation damage occurs when ionizing radiation interferes with the normal operation of a cell causing direct and indirect damage to the cell. • Direct damage occurs when radiation strikes a critical area of the cell (such as the DNA) and causes direct ionization in the molecule itself. • Indirect damage occurs as the result of the formation of very chemically reactive atom groups, called free radicals, within the cell. Free radicals are atoms or groups of atoms that have at least one unpaired electron in the orbital position. Since electrons like to be paired with other electrons, this makes free radicals very reactive. To find a mate for its unpaired electron, a free radical (symbolized by a dot e.g. OH• or H•) will "steal" an electron from a nearby molecule, thus leaving the nearby molecule with a single electron. To fix this, the nearby molecule will steal an electron from yet another molecule. This turns into a chain of chemical reactions, that damages each new molecule that has an electron stolen from it. This can be especially bad if one of those molecules is a molecule of DNA. About 80% of the cell is water. When radiation ionizes water molecules the ions formed interact with other water molecules. H2O radiation H2O+ + e’ H2O+ H+ + OH• H2O + e’ H2O’ H2O’ H• + OH’ Two of the products formed, H• (hydrogen free radical) and OH• (hydroxyl free radical) are very reactive because they have unpaired electrons. Another reaction product in the cell is hydrogen peroxide (H2O2) which is also very reactive. OH• + OH• H2O2 These reactive atom groups can interfere with normal cellular processes by breaking chemical bonds such as the bonds between carbon atoms in the DNA molecule. In living systems, the hydroxyl free radical does not normally occur, because of the strength of the bonds holding the water molecules together. But if anyone is exposed to radiation, these bonds can be broken by the radiation so that hydroxyl radicals result. This is the basis of the dreadful, often fatal, damage that occurs in people with radiation sickness. If hydroxyl radicals attack DNA, chain reactions run along the DNA molecule causing damage to, and mutations in, the genetic material or even actual breakage of the DNA strands. The body does its best to repair this damage by the natural processes of DNA replication, but imperfect repair leaves altered DNA and can give rise to cancer. When strong X- and gamma radiation is deliberately used to kill cancers, it does by producing lar...