Chapter 7 Flashcards
What is ionizing radiation?
Ionizing radiation removes electrons from orbit, creating unstable atoms and can affect DNA and chromosomes
Ionizing radiation also creates free radicals in the body through radiolysis, specifically by radiating water.
What are the three determinants of radiation energy transfer?
- Charge
- Mass
- Energy
These determinants influence the effect of radiation on tissue.
What does LET stand for in radiation biology?
LET stands for Linear Energy Transfer
It refers to the energy deposited as a particle passes through matter.
What is the effect of low LET radiation?
Low LET radiation deposits a small amount of energy, sporadically ionizes, interacts randomly, and is considered sublethal to DNA
Examples include X-rays and gamma rays.
What types of damage can low LET radiation cause?
Causes indirect damage by creating free radicals, which can damage DNA but are usually repaired by enzymes
This type of damage is often considered sublethal.
What characterizes high LET radiation?
High LET radiation is heavy, has long wavelengths, low energy, and loses energy quickly
It causes more ionization over a shorter distance.
What is the biological impact of high LET radiation?
High LET radiation causes more biological damage and is more lethal, especially when internally implanted, injected, inhaled, or ingested
Examples include alpha particles and heavy nuclei.
Fill in the blank: The energy deposited as a particle passes through matter is referred to as ______.
LET
True or False: Low LET radiation gives up energy quickly.
False
Low LET radiation does not give up energy quickly and causes sporadic ionization.
What are the two types of LET radiation?
- Low LET
- High LET
RBE
Relative biological effectiveness
Describes capabilities of radiation w different LETs to cause a particular bio reaction
OER
Oxygen enhancement ratio
Ratio of dose required to cause same response in O2 deprived env to dose required to cause same response in oxygenated conditions
Oxygenated tissues are more radio sensitive
Oxygen fixation Hypothesis
Presence of O2 in tissues causes free radicals to cause permanent bio damage
Molecular level damage
Change in molecule structure that impairs cell function
Damage to reproductive cells may pass on mutations
Direct action damage
Ionization of an atom on the master molecule can cause cell to be inactive or functionally altered
Indirect action damage
Release a free radicals damaging the master molecule usually from radiolysis
Radiation effects on DNA
Single strand breaks can rupture chemical bonds, but repair enzymes are usually able to fix occurs with low LET
Double strand breaks happen with high LET can be lethal on the same wrong leading to chromosome breakage if unrepairable, then mitosis happens, it causes a mutation
Radiation effects on chromosomes
At risk for breakage during interphase, then visible in metaphase, broken ends become chemically active/sticky and adhere either correctly or incorrectly, leads to an anomaly or lesion
Chromosome aberration
Breakage before DNA synthesis so both daughter cells have the mutation
Chromatid abberation
Breakage after DNA synthesis so only one daughter cell will have the mutation
Chromosome structural changes
Restitution-no damage
Deletion-part lost at next division, mutation
Broken and rearrangement -misshapen
Broken and rearrangement without visible damage to chromatid-mutation, looks right attached wrong
What is the master molecule believed to be essential for cell survival?
DNA
It is believed that every cell has a master molecule, which is DNA, that is necessary for its survival.
What happens to a cell after exposure to ionizing radiation if the master molecule is damaged beyond repair?
The cell will die
If the master molecule is not damaged, the cell can survive, although it may still have mutations.
What dose of radiation is associated with instant death of cells?
1000 Gyt
Instant death occurs when a volume of cells is irradiated with a high dose of radiation for seconds or a few minutes.
