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Molecular and cellul

Molecular and Cellular Radiobiology

QuestionAnswer
Are the interactions betwen macromolecules and water the same? No totally different results
What are the effects of macromolecules being radiated in vitro (outside body) vs. in vivo (inside the body)? Outside (in vitro) are less sensitive than in the body (vivo).
What are the three major effects that occur when macro molecules are radiated in vitro? Main-chain scission, cross-linking and point lesions.
What is main-chain scission? The breakage of the backbone of the long chain macromolecule resulting in smaller molecules which may still be macromolecular.
What does main-chain scission reduce? The size of the macromolecule and the viscosity (thickness)of the solution. Measurements of viscosity determine the degree of main-chain scission.
What is cross chain linking? Spur-like projections may be created from radiation, they attach to another macromolecule or segment of the same molecule.
What is Point lesion? Disruption of a single chemical bond-can cause minor modifications in the macromolecule which can affect the entire cell. Thought to be responsible for late radiation effects.
What is Catabolism? Catabolism is destructive-it is the breaking down of large molecules to smaller ones w/ a release of energy.
What is Anabolism? Anabolism is constructive- the process of synthesizing smaller molecules into large ones.
What is metabolism? Consists of catabolism and anabolism.
What can happen with the interruption of metabolism? Any interruption can cause cell death or late effects.
The more macromolecules in a cell the less radiosensitive it is. What order do DNA, RNA and protein molecules fall in? Protein molecules have many copies of macromolecules. RNA have many but less than protein and DNA have only a single copy making it the most radiosensitive.
Damaged chromosomes can be visible or not. Visible damage is bad. Such damage can be reversible or lead to cell death. What can it also affect? The metabolic rate of a cell.
What happens to damage in a germ cell's DNA? The damage may not be visible until future generations.
What is the radiation response of DNA or the types of damage to DNA molecules? Main-chained scission w/ only one side rails severed, Main-chained scission w/ both side rails severed, MCS w/subsequent cross-linking, Rung breakage causing a separation of bases or a change in or loss of a base.
What happens if genetic code is changed? The code is altered and mutations occur at the molecular level.
What happens if change or loss of base occurs? One daughter cell could end up with the wrong code.
What are some effects of DNA damage? Cell death, malignant disease, genetic damage.
Malignant disease and genetic damage are what at what level of response relationship? Linear-non-threshold dose response.
What are the effects of radioplysis on water? When water is irradiated, it dissociates into other molecular products, which is the principal interaction in the body since it is 80% water..
What does ionization of water do? It causes free radicals which are very unstable and exist for less than 1 sec, but can cause point lesions at distant sites. They diffuse easily through the cell.
What do free radicals contain? Energy that is transferred to other molecules disrupting bonds (especially DNA). They can combine and form toxins to the cell:hydrogen peroxide.
What is Direct Effect? When the initial ionizating event occurs on the target molecule (DNA).
What is Indirect Effect? When the initial ionizing event occurs w/ another molecule (usually water)& free radicals are produced, there is energy transferred to DNA.
What is the principal radiation effect on humans? Indirect (80% water). The effects are amplified due to O2 in the human cells (OER)
What is Target Theory? In order for the cell to die, the target molecule (DNA) must be inactivated. When DNA is damaged, there are no other molecules to take its place like in an abundant molecule.
What is a "hit"? When ionization inactivates the target molecule(radiation interacts w/ DNA)
Radiation does not seek target molecules, damage can be from a direct or indirect hit. What interaction does low LET cause? Lesser chance of target interaction w/ low LET. High LET increases probability.
How are lethal effects of radiation studied? By cell survival, not cell death. Cells in a lab are left alone to divide. Many colonies are produced. Irradiated cells produce fewer colonies.
What is the cell survival rate as radiation dose increases? AS dose increases, cell death increases.
What happens to cells that survive irradiation? They can repopulate and will have identical reactions to another radiatiuon dose.
What is the cell cycle time or generation time? Average time from one mitosis to another in a human cell is 10-20 hours.
When are human cells the most radiosensitive and when are they the most radioresistant? Most sensitive during the mitosis stage (*division of cells) and the less sensitive during the interphase (resting phase).
Created by: sewwhat4