Chapter 31 - Molecular Radiobiology

Question 1

the interaction between radiation and tissue occurs at the

Answer 1

electron level

Question 2

observable human radiation injury results from change at the

Answer 2

molecular level

Question 3

the occurrence of molecular lesions is identified by effects on _____and ______

Answer 3

macromolecules and water

Question 4

human body is an

Answer 4

aqueous solution

Question 5

human body contains what percentage of water molecules?

Answer 5

80%

Question 6

controls cellular metabolism and reproduction

Answer 6

DNA

Question 7

when macromolecules are irradiated ______, that is, outside the body or outside the cell, a considerable radiation dose is required to produce a measurable effect.

Answer 7

in vitro

Question 8

irradiation, _____, that is, within the living cell, demonstrates that macromolecules are considerably more radiosensitive in their natural state.

Answer 8

in vivo

Question 9

irradiation outside of the cell or body

Answer 9

in vitro

Question 10

irradiation within the body

Answer 10

in vivo

Question 11

a liquid that contains dissolved substances

Answer 11

solution

Question 12

When macromolecules are irradiated in solution in vitro, THREE MAJOR EFFECTS OCCUR, what are those?

Answer 12

1. main-chain scission
2. cross-linking
3. point lesions

Question 13

the breakage of the backbone of the long-chain macromolecule.

Answer 13

main-chain scission

Question 14

main-chain scission reduces NOT ONLY the size of the macromolecule but also the ______ of the solution

Answer 14

viscosity

Question 15

one that is very thick and slow to flow

Answer 15

viscous solution

Question 16

determine the degree of main-chain scission

Answer 16

measurements of viscosity

Question 17

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 ?

Answer 17

cross-linking

Question 18

Radiation interaction with macromolecules also can result in discruption of single chemical bonds, producing _______

Answer 18

point lesions

Question 19

are not detectable, but they can cause minor modification of the molecule, which in turn can cause it to malfunction within the cell.

Answer 19

Point lesions

Question 20

can result in the stochastic radiation effects observed at the whole-body level

Answer 20

Point lesions

Question 21

the break down of complex molecules

Answer 21

catabolism

Question 22

the break down of complex molecules

Answer 22

catabolism

Question 23

synthesis of macromolecules from smaller molecules

Answer 23

anabolism

Question 24

the genetic code of DNA is transcribed by _____

Answer 24

messenger RNA (mRNA)

Question 25

translates the genetic code of DNA into a protein

Answer 25

transfer RNA (tRNA)

Question 26

proteins are __________ than nucleic acids

Answer 26

less radiosensitive

Question 27

contains the genetic information for each cell

Answer 27

DNA

Question 28

control the growth and development of the cell; these in turn determine the characteristics of the individual

Answer 28

Chromosomes

Question 29

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 ____

Answer 29

deterministic effect

Question 30

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.

Answer 30

Stochastic effect

Question 31

What are the results from irradiation of DNA?

Answer 31

1. Cell death 2. Malignant disease 3. Genetic effects

Question 32

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________

Answer 32

Point mutations

Question 33

is an uncharged molecule that contains a single unpaired electron in the outer shell

Answer 33

free radical

Question 34

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.

Answer 34

Free radicals

Question 35

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.

Answer 35

point mutation

Question 36

results in the formation of ions and free radicals

Answer 36

radiolysis of water

Question 37

poisonous to the cell and therefore acts as a toxic agent.

Answer 37

Hydrogen peroxide

Question 38

is considered to be the principal damaging product after the radiolysis of water

Answer 38

hydroperoxyl radical along with hydrogen peroxide

Question 39

also can be formed by the interaction of two hydrogen peroxyl radicals

Answer 39

Hydrogen peroxide

Question 40

Free radicals are ______ because of their unique structure. This excess energy can be transferred to DNA, and this can result in bond breaks

Answer 40

energetic molecules

Question 41

When the ionizing event occurs on the target molecule, the effect of radiation is

Answer 41

direct

Question 42

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.

Answer 42

indirect

Question 43

The principal effect of radiation on humans is

Answer 43

indirect

Question 44

the most radiosensitive of all macromolecules and is called the target molecule

Answer 44

DNA

Question 45

concept that the biological effects of radiations such as X rays result from ionization

Answer 45

target theory