Chapter 31 - Molecular Radiobiology Flashcards
the interaction between radiation and tissue occurs at the
electron level
observable human radiation injury results from change at the
molecular level
the occurrence of molecular lesions is identified by effects on _____and ______
macromolecules and water
human body is an
aqueous solution
human body contains what percentage of water molecules?
80%
controls cellular metabolism and reproduction
DNA
when macromolecules are irradiated ______, that is, outside the body or outside the cell, a considerable radiation dose is required to produce a measurable effect.
in vitro
irradiation, _____, that is, within the living cell, demonstrates that macromolecules are considerably more radiosensitive in their natural state.
in vivo
irradiation outside of the cell or body
in vitro
irradiation within the body
in vivo
a liquid that contains dissolved substances
solution
When macromolecules are irradiated in solution in vitro, THREE MAJOR EFFECTS OCCUR, what are those?
- main-chain scission
- cross-linking
- point lesions
the breakage of the backbone of the long-chain macromolecule.
main-chain scission
main-chain scission reduces NOT ONLY the size of the macromolecule but also the ______ of the solution
viscosity
one that is very thick and slow to flow
viscous solution
determine the degree of main-chain scission
measurements of viscosity
Some molecules have small, spurlike side structures that extend off the main chain. These side structures can behave as though they had a STICKY SUBSTANCE ON THE END, ans they attach to a neighboring macromolecule or to another segment of the same molecule. This process is called ?
cross-linking
Radiation interaction with macromolecules also can result in discruption of single chemical bonds, producing _______
point lesions
are not detectable, but they can cause minor modification of the molecule, which in turn can cause it to malfunction within the cell.
Point lesions
can result in the stochastic radiation effects observed at the whole-body level
Point lesions
the break down of complex molecules
catabolism
the break down of complex molecules
catabolism
synthesis of macromolecules from smaller molecules
anabolism
the genetic code of DNA is transcribed by _____
messenger RNA (mRNA)
translates the genetic code of DNA into a protein
transfer RNA (tRNA)
proteins are __________ than nucleic acids
less radiosensitive
contains the genetic information for each cell
DNA
control the growth and development of the cell; these in turn determine the characteristics of the individual
Chromosomes
The DNA molecule can be damaged without the production of a visible chromosome aberration. Although such damage is reversible, it can lead to cell death. If enough cells of the same type respond similarly, then a particular tissue or organ can be destroyed. That describes the cause of a ____
deterministic effect
Damage to the DNA also can result in abnormal metabolic activity. Uncontrolled rapid proliferation of cells is the principal characteristic of radiation - induced malignant disease.
Stochastic effect
What are the results from irradiation of DNA?
- Cell death
- Malignant disease
- Genetic effects
the fifth type of damage, the change or loss of of a base, also destroys the triplet code and may not be reversible. This type of radiation damage is a molecular lesion of the DNA. These molecular lesions are called________
Point mutations
is an uncharged molecule that contains a single unpaired electron in the outer shell
free radical
contain excess energy that can be transferred to other molecules to disrupt bonds and produce point lesions at some distance from the initial ionizing event.
Free radicals
results in the change or loss of a base, which creates an abnormal gene. This is therefore a genetic mutation that is passed to one of the daughter cells.
point mutation
results in the formation of ions and free radicals
radiolysis of water
poisonous to the cell and therefore acts as a toxic agent.
Hydrogen peroxide
is considered to be the principal damaging product after the radiolysis of water
hydroperoxyl radical along with hydrogen peroxide
also can be formed by the interaction of two hydrogen peroxyl radicals
Hydrogen peroxide
Free radicals are ______ because of their unique structure. This excess energy can be transferred to DNA, and this can result in bond breaks
energetic molecules
When the ionizing event occurs on the target molecule, the effect of radiation is
direct
If the initial ionizing event occurs on a distant, noncritical molecule, which then transfers the energy of ionization to the target molecule, an ________ effect has occurred.
indirect
The principal effect of radiation on humans is
indirect
the most radiosensitive of all macromolecules and is called the target molecule
DNA
concept that the biological effects of radiations such as X rays result from ionization
target theory
