1what happens at instant death of cell due to radiation
growth disrpution of form and structure (100k rad)
2what happens at reproductive death of cells due to radiation?
permantly loses ability to reproduce @ 1-100 gya
3what happens at mitotic death due to cellular radiation
radiation inhibits mitotic process
4what is mitotic delay
day before next division due to radiation
5what is apotosis
nucleus breaks, cell breaks, then is ingested by neighboring cells
6what is main chain scission
the breakage of backbone of the long change macomolecules
7what is cross linking
afer irradiation, spur like structures can form extending out of the main chain which attach to neighboring macomolecules
8what is point lesion
irradiation results in disruption of single chemical bond (bases are inturrupted)
9what commonly causes point lesions
low L.E.T.
10what is catabolism
the reduction of nutrient molecules for energy
11what is anabolism
production of large moecules for form and function
12what is most radiosensitive molecule?
DNA
15where is DNA located?
in the chromosomes of the cell nucleus
16what are the 3 principle effects radiation has on DNA
cell death, malignant disease, genetic disease
17of the 3 principle effects, which cannot be repaired
genetic disease
18what are the 5 ways radiation damages dna
main-chain scission with one side severed,
mainchain scission w/ both sides severed
main-chain scission and subsquent crosslinking
rung breakage causing seperation of bases
change in or loss of a base
19which of the 5 dna damages may not be reversible
change in or loss of base
20when is chromosome dmg visible
during anaphase and metaphase
21what is aberration
when broken chromosome does not rejoin
22what is restitution
when broken chromosome rejoins (95% time)
23what is radiolysis of water
when water is irradiated it breaks into other molecular products
24how much of human body is made of water
80%
25the priniciple radiation interaction in the body is with what
water
26What happens during the first step of radiolysis of water
radiation interacts with water and initially creats an ion pair of HOH+ and e-
27After the intial interaction of radiolysis of water, what happens
HOH+ and e- can turn back into H20 or e- will find another HOH and create HOH-
28What happens to HOH+ and HOH-
They are unstable and will break apart to H+ and OH* and H* and OH-
29What is final result of radiolysis of water
formation of ion pair (H+ and OH-) and 2 free radicals (H* and OH*)
30What are free radicals
high reactive and unstable, uncharged molecules that contain a single unpaired electron on outer shell
31OH* (hydroxyl) and OH* (hydroxyl) join to produce what?
h202 (hydrogen peroxide)
32H* can join with O2 to form what?
HO2* (hydroperoxyl)
33Hydrogen peroxide can also be formed by what
2 hydroperoxyl radicals joining (HO2*+ HO2* = h2O2+O2)
34HO2 is?
hydrogen peroxyl
35H2O2 is?
hydrogen peroxide
36how do irradiation hits occur
through both indirect and direct effects
37what is direct effect
when the ionizing event occurs on target molecule (dna)
38what is indirect effect
when the ionizing event occurs on distant non-critical molecule (water) then transfers the energy to target molecule (dna)
39how do most effects of irradiation result from
indirect effects
40what is the target molecule or key molecular target
DNA
41what is Target theory
for a cell to die after radiation exposure, the target molecule must be inactivated
42when does a HIT occur
when radiation interacts with the target molecule
43what causes less hits, high or low LET
Low
44Name the two factors that can increase the probability of a hit to the target molecule?
high oxygen levels and high LET
45how are lethal effects of radiation determined
by observing cell survival not cell death
46what is single target, single hit model?
model for radiationdose relationship for simple cells, single target must be inactivated for cell to die
47what is d37
classified as a distributed dose that is sufficient to kill 63% of cell with 37% surviving
48What are low D37
radiosensitive cell
49what are High D37
radioresistant cell
50What is D0
dose necessary to reduce cell survival to 37% (mean lethal dose)
51what is DQ
ability of cell to recover from sublethal dose (threshold dose)
52what is poisson distribution
computes probability of cell death
53sublethal damage must what?
accumulate before the cell dies
54what happens to cells that survive?
grow and repopulate
55cells are able to find and repair damage at what LET
Low LET
56At what LET is mechanism not as effective
High LET
57What is cell cycle time?
the avg time from one mitosis to another
58what cycle phase is the most time variable?
G1 phase
59when can DNA snythesis be effected iff irradiation occurs
during G1 phase
60How does the radiosensitivity of human cells vary with stages of the cell cycle?
Mitosis is most radiosensitive and then G1-S phase. Late S phase is most radioresistant.