Molecular And Cellular Radiobiology Reviewer PDF

MOLECULAR AND CELLULAR CHAPTER 3 REVIEWER | GIRLIES RADIOBIOLOGY EXPOSURE CROSS-LINKING In Vitro – outside the body - Produce small spurlike molecules...

MOLECULAR AND CELLULAR CHAPTER 3 REVIEWER | GIRLIES RADIOBIOLOGY EXPOSURE CROSS-LINKING In Vitro – outside the body - Produce small spurlike molecules extending off the main chain  When macromolecules are irradiated in - Increases the viscosity of the vitro (outside the body or cell), a macromolecular solution. considerable amout of radiation dose is required to produce measurable effect. Note: In Vivo – inside/within the body (RadThera, - Spur, attachment to othe molecule or on NucMed) itself  Irradiation in vivo (within the living cell) demonstrates that macromolecules are considerably more radiosensitive in their POINT LESIONS natural state - Disruption of single chemical bonds. - Not detectable, but can cause minor modification of the molecule, which in IRRADIATION OF MACROMOLECULES turn can cause malfuction within the cell Solution: Note: - A liquid that contains dissolved - Can result in stochastic radiation effects substances. observed at the whole-body level. - A mixture of fluids such as water and - Changes chemical bonds alcohol is also a solution. - Mutations When macromolecules are irradiated in solution IN VITRO, three major effects Overall Note: occur: - These types of radiation effects on o Main-Chain Scission macromolecules are reversible through o Cross Linking o Point Lesions intracellular repair and recovery. MAIN-CHAIN SCISSION - Breakage of the thread or backbone of the long chain macromolecules - Reduction of a long, single molecules into many smaller molecules - Reduces viscosity of the solution Note: - Reduction of viscosity (lumalapot) - Increase viscous means the thickness of fluid increases. - Appearance: naputol ung molecule pag tinamaan ng radiation, kaya nagrereduce ang size. MOLECULAR AND CELLULAR CHAPTER 3 REVIEWER | GIRLIES RADIOBIOLOGY RADIATION EFFECTS ON DNA RADIOLYSIS OF WATER Each cell contains DNA complexed w/ other When water is irradiated, it dissociates into other molecules in the form of chromosomes of the molecular products. same type. When an atom of water is irradiated, it is ionized RADIATION RESPONSE OF DNA and dissociate into 2 ions; - Main Chain Scission with only one side Ionization H20 + ↑  HOH+ + e- rail severed - Main Chain Scission with both side rails severed After intial ionization, a number of reactions can - Main Chain Scission and subsequent happen: cross-linking - Rung Breakage and subsequent cross- 1. First, ion pair may rejoin a stable water linking molecule, NO DAMAGE OCCURS. - Change in or loss of a base 2. Second, if these ions do not rejoin, it is possible for the negative ion (electron) to attach to another water molecule through the ff. reaction to produce a third type of ion: 3rd type of Ion H20 + e-  HOH- (Additional Ionization) The HOH+ and HOH- ions are relatively unstable and can dissociate into smaller molecules as follows: Dissociation HOH+  H+ + HO* HOH –  OH – + H* Note: - Paulit-ulit na cell recovery and cell Final result of radiolysis of water is the formation proliferation can cause abnormality in of ion pair (H+ and OH–) and 2 free radicals (H* the metabolic function which will result and OH*) to abnormal/uncontrolled proliferation which is the determining cause of cancer. The OH* free radical can join with a similar molecule and form HYDROGEN PEROXIDE which is POISONOUS to the cell and therefore act as a TOXIC AGENT. OH* + OH*  H2O2 Note: Free radicals are UNCHARGED MOLECULES that has a sigle unpaired electron in the other shell, and has a short lifetime of