RTT 250 Radiobiology Test 1


the study of effects of ionizing radiations on living things

T/F: energy is directly deposited in a site in the cell.

False, randomly

Can visible changes in the cell from radiation be distinguished from other traumas?


Latent period

biologic changes occur only after a period of time

Types of ionizing radiation

electromagnetic, particulate, manmade

Give examples of electromagnetic radiation

radiowaves, microwaves, infrared waves, UV light, gamma/x-ray radiation

particulate radiation

tiny fast-moving particles that have both energy and mass

How is particulate radiation produced?

disintegration of an unstable atom; alpha or beta particles

Natural radiation comes from:

cosmic radiation, soil, water, plants, animals

What is the biggest source of manmade radiation dose?

medical and dental xrays

SI unit for Rad


What does Gray measure?

absorbed dose

SI unit for Rem


What does Sievert measure?

equivalent dose

The absorption of radiation in biological material may lead to _________ or ______________.

excitation or ionization


electron is raised to higher energy level


orbital electrons ejected

direct action

radiation interacts with a critical molecule in the cell, such as DNA or RNA.

Does high or low LET radiation undergo direct interactions?


indirect action

radiation interacts elsewhere in the cell and eventually damages DNA.

Where does indirect action primarily take place?


Give examples of low LET radiation

x-rays or gamma

What do indirect interactions result in?

free radicals

free radical

atom or molecule that contains an unpaired electron in the outer shell

Is an unpaired electron highly reactive?


ion free radical

both an ion (charged) and a free radical

What do ion free radicals decay to?

free radicals

H2O+ combines with another H2O to form

hydroxyl free radical (OH*)

2 hydroxyl free radicals can combine to form

hydrogen peroxide; very toxic to cell

Single-target, single-hit target theory

theory that just one hit by radiation on a single sensitive target would lead to death of the cell

multitarget single-hit target theory

just one hit by radiation on each of n sensitive targets in the cell is required for death of the cell

LET (linear energy transfer)

amount of radiation deposited per unit path per unit of radiation

unit for LET


What does LET measure?

rate at which energy is transferred from ionizing radiation to tissue

increase mass= ___________ LET


increase charge = ____________LET


no mass/ no charge = _________LET


examples of high LET radiation

alpha, neutrons

Examples of low LET radiation

x and gamma

Increase LET=___________RBE


Relative Biological Effectiveness (RBE)

ratio of absorbed doses from different types of radiation and their ability to produce the same biological effect

lowest to highest LET equipment

superficial, orthovoltage, Co-60, LINAC

RBE is based off a dose of

250 KeV

RBE equation

D250/Dr (dose of some "test" radiation)

dose equivalent

allows comparison of doses from different "types" of radiation

100 REM = __________ Sv

1 Sv

dose equivalent

dose x quality factor specific to type of radiation

quality factor of photons


quality factor of neutrons


quality factor of alpha particles



The basic unit of structure and function in living things

cellular composition

membrane, cytoplasm, organelles, nucleus

cell membrane function

Controls the movement of substances into and out of the cell; selectively permeable


site of all metabolic functions in the cell


building up, synthesis


breaking down

protoplasm composed of:

water, organic compounds, inorganic compounds

inorganic compounds

mineral salts (sodium-outside cell, potassium- inside cell)

organic compounds found in cell

proteins, carbohydrates, nucleic acids, lipids


building blocks; 15% of cell content

examples of proteins

insulin, egg whites, gelatin, hemoglobin

Proteins include

structural proteins, enzymes, hormones, antibodies

What is the primary source of energy in the cell


nucleic acids

1% of the cell, DNA and RNA

bases of RNA

adenine, guanine, cytosine, uracil

bases of DNA

Adenine, Thymine, Guanine, Cytosine

lipids function

stores energy, insulates, protects and supports organs, and aids in digestion

most sensitive part of the cell


Adenine pairs with

Thymine or Uracil

Guanine pairs with




DNA strand

double stranded structure twisted upon itself to form a tightly coiled molecule that resembles a spiral staircase


complex structures in the nucleus that contain DNA and special proteins


alteration in the sequence of DNA

if a mutation is severe enough, what can be caused?

cell death

Endoplasmic reticulum

involved in protein synthesis; smooth or rough, houses the ribosomes; allows cell parts to communicate with each other


composed of protein and RNA; role in protein synthesis


power house of the cell; produce energy for cellular functions


garbage disposer of the cell; contains special enzymes to breakdown protein, DNA, and some carbohydrates

Golgi complex

packaging area for products manufactured by the cell for export; carbohydrate synthesis

S phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.


most radiosensitive

What phase is the most radioresistant



period between division


process of somatic cells dividing; PMAT


chromatin becomes filamentous and visible


middle"; chromatids aligned in center of cell


apart"; migration of chromatids along spindle to opposite poles of the cell


reconstruction of the nuclear membrane and cytokinesis

germ cells

oogonium of female and spermatogonium of male

cell division of germ cells



cell divides twice but chromosomes are duplicated only once

stem cells

unspecialized cells that retain the ability to become a wide variety of specialized cells


one copy of DNA info


2 copies of DNA

cellular differentiation

The process by which a cell becomes specialized in order to perform a specific function, as in the case of a liver cell, a blood cell, or a neuron.

poorly differentiated

cell is more abnormal than normal looking cell

What is the standard international unit of absorbed dose?


Are x-rays directly or indirectly ionizing?


Low LET deposits little energy over a __________- distance


If low LET radiation more biologically damaging or more?


As LET increases, radiation produces _____ cell killing per Gray.


RBE depends on LET, and rises to a maximum at an LET of about 100 keV/um then falls for higher values of LET because of ______________



response of cells to radiation is strongly dependent on oxygen

OER is the ratio of

hypoxic-to-aerated doses

OER equation

hypoxic dose/aerated dose

OER greater than 1

takes more dose to "kill" hypoxic cells

As LET increases, OER ______________-


the oxygen effect is more pronounced with what kind of radiation

x and gamma rays

OER for most mammalian cells


Are hypoxic or aerated cells easier to kill with radiation?

aerated; hypoxic cells generally need a higher dose to produce the same effect

What is the smallest unit of protoplasm capable of independent existence?


The most abundant constituent of protoplasm is _________, which is approximately ______________ water

water; 70-85%

What are the building blocks of a protein?

amino acids

Name 3 components of a carbohydrate

carbon, hydrogen, oxygen

Carbohydrates are the primary source of __________ of the cell


What are the 2 nucleic acids in the cell?


3 functions of lipids in a cell

store energy, insulation, supports organs

Site of all metabolic functions in the cell?


What physically separates the nucleus from the cytoplasm?

nuclear envelope

What does DNA stand for?

deoxyribonucleic acid

How many nitrogenous bases are present in DNA?


What are the 2 categories of nitrogenous bases?

purines and pyrimidines

T/F: a purine will only pair with another purine


Define the term mutation

alteration in sequence of DNA

What type of ells divide by the process of mitosis

somatic cells


Division of the cytoplasm during cell division

Based on the site of interaction, the action of radiation of the cell can be classified as __________ or _____________

direct or indirect

T/F: direct action is most likely to occur after exposure to high LET radiation


What is the common name for H2O2 and what effect does it have on the cell?

hydrogen peroxide; toxic to the cell