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Questions and Answers
What is the primary result of main-chain scission in macromolecules?
What is the primary result of main-chain scission in macromolecules?
- Breakage of long chains into smaller molecules (correct)
- Increase in chain length
- Increase in viscosity of the solution
- Stabilization of molecule structure
Which consequence occurs as a result of radiation-induced main-chain scission?
Which consequence occurs as a result of radiation-induced main-chain scission?
- Complete degradation of the molecule
- Increased molecular weight
- Strengthening of the DNA structure
- Reduction of solution viscosity (correct)
What does the radiolysis of water produce upon ionization?
What does the radiolysis of water produce upon ionization?
- Ozone and hydrogen gas
- Hydroxyl radicals and electrons (correct)
- Carbon dioxide and sulfur dioxide
- Stable water molecules only
What happens if the ion pairs formed during radiolysis of water do not recombine?
What happens if the ion pairs formed during radiolysis of water do not recombine?
What is indicated by main-chain scission with both side rails severed?
What is indicated by main-chain scission with both side rails severed?
What is produced as a result of the reaction of water with an electron?
What is produced as a result of the reaction of water with an electron?
Which ions are formed through the dissociation of HOH+?
Which ions are formed through the dissociation of HOH+?
What do OH* free radicals combine to form?
What do OH* free radicals combine to form?
Which of the following statements is true about free radicals?
Which of the following statements is true about free radicals?
What effect can prolonged cell recovery and proliferation have on cells?
What effect can prolonged cell recovery and proliferation have on cells?
What occurs more readily when macromolecules are irradiated in vivo compared to in vitro?
What occurs more readily when macromolecules are irradiated in vivo compared to in vitro?
Which of the following describes the process of cross-linking in irradiated macromolecules?
Which of the following describes the process of cross-linking in irradiated macromolecules?
What is a notable effect of point lesions on macromolecules?
What is a notable effect of point lesions on macromolecules?
What happens to the viscosity of a macromolecular solution due to cross-linking?
What happens to the viscosity of a macromolecular solution due to cross-linking?
Which of the following best describes what a solution is in the context of irradiated macromolecules?
Which of the following best describes what a solution is in the context of irradiated macromolecules?
How do the types of radiation effects on macromolecules recover after damage?
How do the types of radiation effects on macromolecules recover after damage?
Which type of radiation effect results in changes to chemical bonds without being detectable?
Which type of radiation effect results in changes to chemical bonds without being detectable?
What describes the nature of macromolecules exposed to irradiation in vitro?
What describes the nature of macromolecules exposed to irradiation in vitro?
Flashcards
In Vitro Exposure
In Vitro Exposure
Radiation exposure outside a living organism, typically in a lab setting.
In Vivo Exposure
In Vivo Exposure
Radiation exposure within a living organism.
Main-Chain Scission
Main-Chain Scission
Breaking of a chemical bond along the main chain of a macromolecule, following radiation exposure.
Cross-Linking
Cross-Linking
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Point Lesions
Point Lesions
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Macromolecule Irradiation (Solution)
Macromolecule Irradiation (Solution)
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Stochastic Radiation Effects
Stochastic Radiation Effects
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Macromolecule Radiosensitivity
Macromolecule Radiosensitivity
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Radiolysis of Water
Radiolysis of Water
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HOH+ and HOH-
HOH+ and HOH-
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H+ and OH-
H+ and OH-
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Free Radicals
Free Radicals
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Hydrogen Peroxide (H2O2)
Hydrogen Peroxide (H2O2)
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What happens to water when it's irradiated?
What happens to water when it's irradiated?
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What are the possible fates of ionized water?
What are the possible fates of ionized water?
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How does main-chain scission affect viscosity?
How does main-chain scission affect viscosity?
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What is the appearance of a molecule after main-chain scission?
What is the appearance of a molecule after main-chain scission?
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Study Notes
Exposure
- In Vitro irradiation (outside the body) of macromolecules requires a significant radiation dose to produce measurable effects.
- In Vivo irradiation (inside the body) shows macromolecules are more radiosensitive in their natural state.
Irradiation of Macromolecules
- Solutions are liquids containing dissolved substances, including mixtures like water and alcohol.
- Irradiation of macromolecules in solution (in vitro) can cause three main effects:
- Main-chain scission: Breaking the backbone of long chain macromolecules into smaller molecules, reducing solution viscosity.
- Cross-linking: Formation of spur-like molecules extending from the main chain, increasing solution viscosity.
- Point lesions: Disruption of single chemical bonds, causing minor modifications and potential malfunction within the cell.
- Stochastic radiation effects can be observed at the whole-body level.
- These effects are usually reversible through intracellular repair processes.
Radiolysis of Water
- Irradiation of water causes ionization and dissociation into H2O+ and free electrons.
- Ion pairs may rejoin without damage, or the free electron can create additional ions (e.g., HOH-).
- Dissociation of HOH+ and HOH- ions can produce hydroxyl and hydrogen radicals (highly reactive).
- Hydroxyl radicals can combine to form hydrogen peroxide, a toxic agent to cells.
Radiation Response of DNA
- DNA is complexed with other molecules within chromosomes.
- Radiation can cause various types of damage to DNA, including:
- Main-chain scission (single or double strand breaks)
- Cross-linking
- Rung breakage
- Base changes
- Repeated cell recovery and proliferation can lead to metabolic dysfunction and uncontrolled cell proliferation (cancer).
Macromolecular Synthesis
- Anabolism involves building larger molecules from smaller ones.
- Catabolism involves breaking down larger molecules into smaller ones.
Target Theory
- Cell death occurs when a crucial target molecule (e.g., DNA) is inactivated.
- Interactions between radiation and the target are called Hits.
Direct and Indirect Effects
- Direct effects occur when radiation interacts directly with the target molecule (DNA), often leading to cell death.
- Indirect effects involve radiation interacting with water molecules, forming free radicals that damage other cellular components, potentially avoiding direct cell death.
Cell Survival Kinetics
- Single-target, single-hit models apply to simple biological targets like enzymes, viruses, and bacteria.
- Multi-target, single-hit models apply to more complex systems like human cells.
- Both models use values like D37 (dose where 37% of cells survive) and extrapolation number (n) to quantify cell radiosensitivity.
- Cell radiosensitivity can be measured using these models as well regarding the effect of various radiation types and doses on the relative cell survival.
Extrapolation Number
- A measure of the shoulder width in cell survival curves.
- Larger values suggest greater capacity for cell recovery from sublethal damage.
Oxygen Enhancement Ratio (OER)
- A measure of the effect of oxygen on radiation sensitivity.
- Oxygen presence maximizes low-LET radiation effects and increases a need for a higher dose to achieve the same effect in Anoxic cells.
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