Irradiation of Macromolecules Quiz

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Questions and Answers

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?

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?

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?

They can attach to other water molecules. (C) Signup and view all the answers

What is indicated by main-chain scission with both side rails severed?

Significant damage to the DNA structure (C) Signup and view all the answers

What is produced as a result of the reaction of water with an electron?

HOH- (C) Signup and view all the answers

Which ions are formed through the dissociation of HOH+?

H+ and HO* (C) Signup and view all the answers

What do OH* free radicals combine to form?

Hydrogen Peroxide (A) Signup and view all the answers

Which of the following statements is true about free radicals?

They contain an unpaired electron. (C) Signup and view all the answers

What effect can prolonged cell recovery and proliferation have on cells?

Result in cancer (C) Signup and view all the answers

What occurs more readily when macromolecules are irradiated in vivo compared to in vitro?

Macromolecules are more radiosensitive. (C) Signup and view all the answers

Which of the following describes the process of cross-linking in irradiated macromolecules?

Production of spur-like molecules off the main chain. (D) Signup and view all the answers

What is a notable effect of point lesions on macromolecules?

They cause disruptions of single chemical bonds. (B) Signup and view all the answers

What happens to the viscosity of a macromolecular solution due to cross-linking?

It increases. (A) Signup and view all the answers

Which of the following best describes what a solution is in the context of irradiated macromolecules?

A liquid containing dissolved substances. (B) Signup and view all the answers

How do the types of radiation effects on macromolecules recover after damage?

They are reversed through intracellular repair. (C) Signup and view all the answers

Which type of radiation effect results in changes to chemical bonds without being detectable?

Point lesions. (C) Signup and view all the answers

What describes the nature of macromolecules exposed to irradiation in vitro?

A considerable amount of radiation is required for measurable effect. (D) Signup and view all the answers

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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Description

Test your understanding of the effects of irradiation on macromolecules both in vitro and in vivo. This quiz explores key concepts like main-chain scission, cross-linking, and point lesions, while addressing their implications for cell function. Challenge yourself on the responses of macromolecules to radiation exposure in different environments.