Radiation Effects and Electromagnetic Properties

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Questions and Answers

What is the relationship between frequency and wavelength in electromagnetic radiation?

High frequency corresponds to high wavelength.

They have no relationship.

High frequency corresponds to low wavelength. (correct)

They are directly proportional.

Which type of radiation has an energy level of more than 10 eV?

Exciting radiation

Thermal radiation

Ionizing radiation (correct)

Non-ionizing radiation

What happens during the process of ionizing radiation?

Electrons are ejected from the atom. (correct)

Atoms lose their nucleus.

Electrons are excited to higher orbits.

Atoms gain thermal energy.

What is the effect of UV radiation categorized as UVC?

UVC is absorbed by the atmosphere before reaching the Earth's surface. Signup and view all the answers

Which of the following equations represents the energy of radiation?

E=h/λ Signup and view all the answers

What is the primary factor determining the susceptibility of biological molecules to direct radiation damage?

The size of the molecule Signup and view all the answers

Which statement accurately describes indirect radiation damage?

It results from the interaction of ionizing radiation with water. Signup and view all the answers

What type of damage can occur in nucleic acids due to direct radiation effects?

Breakage of hydrogen bonds in DNA Signup and view all the answers

In terms of direct effects of radiation, which of the following molecules is most likely to be affected?

DNA Signup and view all the answers

Which outcome is NOT associated with direct effects of radiation on proteins?

Single-strand breakage Signup and view all the answers

What is considered the most important cause of ionizing radiation injury in tissues?

Formation of hydroxyl radicals Signup and view all the answers

Which of the following is a reactive oxygen species produced by the reaction of hydrogen radicals with molecular oxygen?

Hydroperoxide radical Signup and view all the answers

How can endogenous antioxidants convert harmful molecules into harmless substances?

By neutralizing reactive oxygen species Signup and view all the answers

What factor influences the radiosensitivity of various tissues?

Amount of oxygen present in the tissue Signup and view all the answers

Which of the following antioxidants is considered exogenous?

Vitamin C Signup and view all the answers

Study Notes

Radiation Damage

Radiation damage results from direct or indirect action.
Direct action occurs when radiation directly affects the biological molecules.
Indirect action is from free radicals formed by radiation reacting with water.
Larger molecules are more likely to be affected by radiation.
Damage to DNA is the main cause of the damaging effects.
The dose/effect ratio is extremely variable, depending on many factors, like the type of radiation, radiation modes (external or internal), and extent of body surface area.

Biological Effects of IR

Effects on living organisms vary depending on the type of radiation and the level of exposure.
Acute effects occur from a high dose in a short period. Chronic effects are from continuous, prolonged, low-dose exposure.
Somatic effects are on body tissues, and genetic effects are on reproductive cells.
The most radiosensitive tissues have a high cell division rate, such as bone marrow, skin, and intestinal mucosa, as well as germ cells.

Types of Radiation

Ionizing Radiation: Capable of directly or indirectly ionizing atoms and molecules. Energy ≥ 10 eV.
- Corpuscular: Subatomic particles, high speed, often near the speed of light (alpha, beta particles). These are directly ionizing (neutrons are also a possibility of ionizing radiation).
- Electromagnetic: Photons traveling at the speed of light (x-rays, gamma rays). These are indirectly ionizing.
Non-ionizing Radiation: Does not have enough energy to ionize atoms and molecules. Energy <10 eV.
- Optical: Ultraviolet, infrared, visible light (including lasers)
- Radiofrequency: Including microwaves.
- Extremely low frequency

Sources of Exposure

Natural: Cosmic rays, radioactive elements such as uranium, radon (a radioactive, colorless, tasteless gas).
Artificial: Radiopharmaceuticals, radiotherapy, radiodiagnostics, and research.

Classification of Electromagnetic Radiation

Ionizing radiation has wavelengths from very short (gamma rays and X rays), to slightly longer (ultraviolet).
Non-ionizing radiation covers the majority of the spectra, from longer wavelengths (visible light, infrared) to the longest wavelengths (radio waves)

UV Radiation

UVA (400-320 nm) is the most abundant, penetrates deeply
UVB (320-290 nm) primarily causes sunburn but is also responsible for some types of skin cancer
UVC is the most dangerous, mostly absorbed by the atmosphere preventing most from reaching us

Mechanisms of UV Damage

Direct photochemical mechanism: matter absorbs energy generating an excited molecule.
Cutaneous chromophores: purine and pyrimidine bases of nucleic acids, melanin, amino acids, lipids. Endogenous -in body. Exogenous -outside body, such as tattoo ink.
Formation of Thymine Dimers is a serious DNA lesion altering genetic information.

Reactive Oxygen Species

Generated from radiation interacting with oxygen in tissues, resulting in free radicals such as hydroxyl radicals, and hydrogen peroxide
Different tissues have varied susceptibility due to differing oxygen tension (pO2) and antioxidant quantity.

Radiotherapy

Based on directing ionizing radiation at tumor cells to damage their DNA more effectively than healthy cells.
Oxygen is important for cytotoxicity of cancer cells, and cancer cells with lower oxygen levels are less sensitive to radiotherapy.
Techniques to increase oxygenation or decrease oxygen in healthy tissues around tumors are being tested to improve the effectiveness of radiotherapy.

Radioisotope Examples

Fluoro-18(F-18): To detect metabolic activity, especially to diagnose tumors in brain.
Carbon-11(C-11): For studying cerebral perfusion and other biological reactions in the central nervous system.
Oxygen-15(O-15): To assess cardiac perfusion and blood flow of the brain.
Nitrogen-13(N-13): To assess cardiac perfusion.

X-ray Radiography

X-rays pass through different tissues to varying degrees depending on the atomic number and thickness of the tissue.
Dense tissues like bones are almost completely crossed, making them light colored on the image (radiograph).
Partially crossed tissues, like muscles and vessels, appear gray
Tissues that pass through the rays appear dark, like lungs.

Principles of PET Imaging

Uses radioisotopes that emit positrons during radioactive decay.
Detecting emitted positrons allows generating images (PET) that show various biological processes in living tissues.

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Description

Explore the complex relationship between frequency and wavelength in electromagnetic radiation through this quiz. Delve into the types of radiation, their energy levels, and the effects of ionizing radiation on biological molecules. Test your knowledge on direct and indirect damage caused by radiation and the role of reactive oxygen species.