Molecular and Cellular Radiation Biology Flashcards
(40 cards)
Radiation Biology
Radiation biology is the branch of biology concerned with the effects of what on living systems?
Includes:
- Sequence of events occuring after the ___ of energy from ___ radiation
- Action of the living system to make up for the ___ of this energy ___
- ___ to the living system that may be produced
Radiation Biology
Radiation biology is the branch of biology concerned with the effects of IONIZING RADIATION on living systems.
Includes:
- Sequence of events occuring after the ABSORPTION of energy from IONIZING radiation
- Action of the living system to make up for the CONSEQUENCES of this energy ASSIMILATION
- INJURY to the living system that may be produced
Ionizing Radiation
Ionizing radiation damages living systems by ionizing the ___ comprising the ___ structure of these systems.
What is begun with the ionization produced by various types of radiation?
What are the types of radiation?
What will not bond properly in molecules?
Ionizing Radiation
Ionizing radiation damages living systems by ionizing the ATOMS comprising the MOLECULAR structure of these systems.
What is begun with the ionization produced by various types of radiation? BIOLOGICAL DAMAGE
What are the types of radiation? GAMMA RAYS (1), ALPHA PARTICLES (20), BETA PARTICLES (2), PROTONS (2), X-RAYS (1)
What will not bond properly in molecules? IONIZED ATOMS
Radiation Energy Transfer Determinants
Ionizing radiation causes ___ and the effects may vary in biologic tissue.
What three important concepts help us understand that?
Radiation Energy Transfer Determinants
Ionizing radiation causes INJURY and the effects may vary in biologic tissue.
What three important concepts help us understand that?
- RELATIVE BIOLOGIC EFFECTIVENES
- OXYGEN ENHANCEMENT RATIO
- LINEAR ENERGY TRANSFER
Linear Energy Transfer (LET)
LET is the average energy deposited per unit ___ of ___ by ___ radiation as it passes through and interacts with a ___ along its path.
What units is LET described in?
What is the rate of transfer from diagnostic to soft tissue?
Linear Energy Transfer (LET)
LET is the average energy deposited per unit LEGNTH of TRACK by IONIZING radiation as it passes through and interacts with a MEDIUM along its path.
What units is LET described in? keV/μm
What is the rate of transfer from diagnostic to soft tissue? 3 keV/μm
Linear Energy Transfer (LET)
LET is a very important factor in assessing potential ___ and ___ damage from exposure to ionizing radiation.
What are the 2 radiation categories according to LET?
When LET increases (more absorption), the chances of producing a significant biologic response in the ___ biologic response in the ___ ___ molecules grows (increases).
Linear Energy Transfer (LET)
LET is a very important factor in assessing potential TISSUE and ORGAN damage from exposure to ionizing radiation.
What are the 2 radiation categories according to LET?
- LOW-LINEAR ENERGY TRANSFER RADIATION (kVp)
- HIGH-LINEAR ENERGY TRANSFER RADIATION (MeV)
When LET increases (more absorption), the chances of producing asignificant biologic response in the RADIOSENSITIVE biologic response in the RADIOSENSITIVE DNA molecules grows (increases).
General Categories of Linear Energy Transfer Radiation
What are the low-LET types of radiation? (2)
What are the high-LET types of radiation? (4)
General Categories of Linear Energy Transfer Radiation
What are the low-LET types of radiation? (2)
- Gamma Rays
- X-Rays
What are the high-LET types of radiation? (4)
- Charged particles released from interactions between neutrons and atoms
- Alpha Particles
- Low-energy neutrons
- Ions of heavy nuclei
Low – LET Energies
- Has no ___ or no ___
- Is ___ ionizing and interacts ___ along the length of its track
- Causes ___ through ___ interactions (releases ___ ___)
- Causes sublethal damage to the ___ or ___ ___
Low – LET Energies
- Has no MASS or no CHARGE
- Is SPARSELY ionizing and interacts RANDOMLY along the length of its track
- Causes DAMAGES through INDIRECT interactions (releases FREE RADICALS)
- Causes sublethal damage to the DNA or REPAIR ENZYMES
High-LET and Internal Contamination
High LET an internal contamination are radionuclides that are what?
___ damage due to ___ breaks in the ___ are possible.
High-LET and Internal Contamination
High LET an internal contamination are radionuclides that are what?
- IMPLANTED
- INGESTED
- INJECTED
- INHALED
IRREPARABLE damage due to STRAND breaks in the DNA are possible.
LET Energies Comparisons
The higher the LET of radiation, the greater the change for a ___ ___.
What is the LET for the following radiation types?
- Cobalt – 60
- 1 MeV Electrons
- Diagnostic x-ray
- 10 MeV
- 2.5 mEv
- 5 mEv
- Heavy nuclei
LET Energies Comparisons
The higher the LET of radiation, the greater the change for a BIOLOGIC REACTION.
What is the LET for the following radiation types?
- Cobalt – 60 … 0.25
- 1 MeV Electrons … 0.3
- Diagnostic x-ray … 3.0
- 10 MeV … 4.0
- 2.5 mEv … 20.0
- 5 mEv … 100.0
- Heavy nuclei … 1000.0
Relative Biologic Effectiveness (RBE)
- Describes the relative capabilities of radiation with differing ___ to produce a particular biologic reaction
- RBE of the type of radiation being used is the ratio of the dose of a ___ radiation (conventionally ___-kVp x-rays) to the dose of radiation of the type in question that is necessary to produce the ___ biologic reaction in a given experiment. The reaction is produced by a dose of the ___ radiation delivered under the ___ conditions.
Relative Biologic Effectiveness (RBE)
- Describes the relative capabilities of radiation with differing LETs to produce a particular biologic reaction
- RBE of the type of radiation being used is the ratio of the dose of a REFERENCE radiation (conventionally 250-kVp x-rays) to the dose of radiation of the type in question that is necessary to produce the SAME biologic reaction in a given experiment. The reaction is produced by a dose of the TEST radiation delivered under the SAME conditions.
Mathematical Expression of Relative Biologic Effectiveness
Mathematical Expression of Relative Biologic Effectiveness
RBE
Dose of ___ radiation necessary to produce a ___ effect
Dose of ___ radiation necessary to produce the ___ effect
• When mice are irradiated with 250 keV x-rays, death occurs at 650 rads. If similar mice are irradiated with fast neutrons, death occurs at only 210 rad. What is the RBE for the fast neutrons?
RBE = 650 rad = 3.1
210 rad
RBE
Dose of STANDARD radiation necessary to produce a GIVEN effect
Dose of TEST radiation necessary to produce the SAME effect
• When mice are irradiated with 250 keV x-rays, death occurs at 650 rads. If similar mice are irradiated with fast neutrons, death occurs at only 210 rad. What is the RBE for the fast neutrons?
RBE = 650 rad = 3.1
210 rad
Oxygen Enhancement Ratio (OER)
- The ratio of the radiation dose required to cause a particular biologic response of ___ or ___ in any oxygen-deprived environment to the radiation dose required to cause an ___ response under ___ oxygenated conditions
- In general, x-rays and gamma rays have an OER of about ___ when radiation dose is ___.
- OER may be ___ (approximately ___) when radiation doses are below ___ Gyt.
Oxygen Enhancement Ratio (OER)
- The ratio of the radiation dose required to cause a particular biologic response of CELLS or ORGANISMS in any oxygen-deprived environment to the radiation dose required to cause an IDENTICAL response under NORMAL oxygenated conditions
- In general, x-rays and gamma rays have an OER of about 3.0 when radiation dose is HIGH.
- OER may be LESS (approximately 2.0) when radiation doses are below 2 Gyt.
Oxygen Enhancement Ratio (OER)
The response of ___ to radiation is ___ when irradiated in the oxygenated or ___ state.
- It is theorized that oxygen is needed in order for ___ ___ to form during ionization of ___.
- With the free radicals, ___ ___ is not formed and thus ___ damage is ___.
Oxygen Enhancement Ratio (OER)
The response of TISSUE to radiation is GREATER when irradiated in the oxygenated or AEROBIC state.
- It is theorized that oxygen is needed in order for FREE RADICALS to form during ionization of WATER.
- With the free radicals, HYDROGEN PEROXIDE is not formed and thus CELL damage is REDUCED.
Molecular Effects of Irradiation
In living systems, biologic damage resulting from exposure to ionizing radiation may be observed on what three levels?
- Any ___ radiation-induced ___ of living systems at the ___ or ___ level always begin with damage at the ___ level.
- Molecular damage results in the formation of ___ changed molecules that may impair ___ ___.
Molecular Effects of Irradiation
In living systems, biologic damage resulting from exposure to ionizing radiation may be observed on what three levels? MOLECULAR, ORGANIC, CELLULAR
- Any VISIBLE radiation-induced INJURIES of living systems at the CELLULAR or ORGANIC level always begin with damage at the MOLECULAR level.
- Molecular damage results in the formation of STRUCTURALLY changed molecules that may impair CELLULAR FUNCTIONING.
Effects of Irradiation on Somatic and Genetic Cells
- exposure to ionizing radiation can alter a human cell’s ___ ___.
- may disturb the cell’s ___ balance and ultimately the way it ___. The affected cell can then no longer ___ its ___ task.
- If a sufficient quantity of ___ cells are affected, entire ___ processes may be ___.
- If radiation damages the ___ cells, the damage may be passed on to future generations in the form of ___ ___.
Effects of Irradiation on Somatic and Genetic Cells
- exposure to ionizing radiation can alter a human cell’s CONSTITUENT MOLECULES.
- may disturb the cell’s CHEMICAL balance and ultimately the way it OPERATES. The affected cell can then no longer PERFORM its NORMAL task.
- If a sufficient quantity of SOMATIC cells are affected, entire BODY processes may be DISRUPTED.
- If radiation damages the GERM cells, the damage may be passed on to future generations in the form of GENETIC MUTATIONS.
Classification of Ionizing Radiation Interaction
What are two classifications of ionizing radiation interaction on a cell?
Essentially all effects of ___ in living cells result from ___ action, because the human body is composed of ___% ___ and less than ___% ___.
Classification of Ionizing Radiation Interaction
What are two classifications of ionizing radiation interaction on a cell?
- DIRECT ACTION (EX, IN DNA)
- INDIRECT ACTION (EX, IN WATER)
Essentially all effects of IRRADIATION in living cells result from INDIRECT action, because the human body is composed of 80% WATER and less than 1% DNA.
Direct and Indirect Action
Direct and Indirect Action
Radiolysis of Water (Indirect)
- Ionization of….
- Production of…
- Production of undesirable…
- Production of …. substances
- Organic … formation
Radiolysis of Water (Indirect)
- Ionization of WATER MOLECULES
- Production of FREE RADICALS
- Production of undesirable CHEMICAL REACTIONS AND BIOLOGIC DAMAGE
- Production of CELL-DAMAGING substances
- Organic FREE RADICAL formation
Effects of Ionizing Radiation on DNA
Single-strand break
Ionizing radiation interacts with ___ ___, ___ ___, and ___ one of the molecule’s ___ ___ possibly ___ one of the sugar-phosphate chain ___ rails (called a ___ ___).
___ ___ are often capable of reversing this damage.
Effects of Ionizing Radiation on DNA
Single-strand break
Ionizing radiation interacts with DNA MACROMOLECULE, TRANSFERS ENERGY, and RUPTURES one of the molecule’s CHEMICAL BONDS possibly SEVERING one of the sugar-phosphate chain SIDE rails (called a POINT MUTATION).
REPAIR ENZYMES are often capable of reversing this damage.
Effects of Ionizing Radiation on DNA
Double-strand break
- Further exposure of the affected DNA macromolecule to ionizing radiation can lead to ___ ___ in the sugar-phosphate molecular chain(s).
- Breaks may also be ___ but are not repaired as easily as ___ ___ breaks.
- If repair does not take place, further ___ may occur in the DNA chains, threatening the ___ of the ___.
- Occur more commonly with ___ ___ (___ ___) radiation.
Effects of Ionizing Radiation on DNA
Double-strand break
- Further exposure of the affected DNA macromolecule to ionizing radiation can lead to ADDITIONAL BREAKS in the sugar-phosphate molecular chain(s).
- Breaks may also be REPAIRED but are not repaired as easily as SINGLE STRAND breaks.
- If repair does not take place, further SEPARATION may occur in the DNA chains, threatening the LIFE of the CELL.
- Occur more commonly with DENSELY IONIZING (HIGH-LET) radiation.
Effects of Ionizing Radiation on DNA
Double-strand break in same Rung of DNA
- Result is a ___ or broken ___ with each new portion containing an ___ amount of ___ material
- If damaged ___ divides, each new ___ cell will receive an ___ amount of ___ material culminating in the ___ or ___ functioning of the new ___ cell.
Effects of Ionizing Radiation on DNA
Double-strand break in same Rung of DNA
- Result is a CLEAVED or broken CHROMOSOME with each new portion containing an UNEQUAL amount of GENETIC material
- If damaged CHROMOSOMES divides, each new DAUGHTER cell will receive an INCORRECT amount of GENETIC material culminating in the DEATH or IMPAIRED functioning of the new DAUGHTER cell.
Effects of Ionizing Radiation on DNA
Mutation
- In general, interaction of high-energy radiation with a DNA molecule causes either a ___ of or ___ in a ___ ___ on the DNA chain.
- Direct consequence of this damage is an ___ of the ___ ___, a ___.
- May not be ___ and may cause ___ consequences for the cell
- If cell remains ___, ___ ___ information will be ___ to one of the ___ ___ cells when the cell ___.
Effects of Ionizing Radiation on DNA
Mutation
- In general, interaction of high-energy radiation with a DNA molecule causes either a LOSS of or CHANGE in a NITROGENOUS BASE on the DNA chain.
- Direct consequence of this damage is an ALTERATION of the BASE SEQUENCE, a MUTATION.
- May not be REVERSIBLE and may cause ACUTE consequences for the cell
- If cell remains VIABLE, INCORRECT GENETIC information will be TRANSFERRED to one of the TWO DAUGHTER cells when the cell DIVIDES.
Effects of Ionizing Radiation on DNA
Covalent cross-links
- ___ unions created between atoms by the ___ sharing of ___ or ___ pairs of electrons
- Initiated by ___ ___ radiation
- Following irradiation, some molecules can ___ or change into ___, ___ molecules that become very ___ (“___”) when they themselves are exposed to ___, causing these molecules to ___ to other ___ or to other segments of the same ___ chain.
- Can occur in many different ___
- ___ cross-link
- ___ cross-link
Effects of Ionizing Radiation on DNA
Covalent cross-links
- CHEMICAL unions created between atoms by the SINGLE sharing of ONE or MORE pairs of electrons
- Initiated by HIGH ENERGY radiation
- Following irradiation, some molecules can FRAGMENT or change into SMALL, SPURLIKE molecules that become very INTERACTIVE (“STICKY”) when they themselves are exposed to RADIATION, causing these molecules to ATTACH to other MACROMOLECULES or to other segments of the same MACROMOLECULE chain.
- Can occur in many different PATTERNS
- INTRASTRAND cross-link
- INTERSTRAND cross-link
