Direct and Indirect Actions of Radiation Damage

A set of vocabulary flashcards covering the molecular processes, mechanisms, and biological consequences of direct and indirect radiation damage to cells.

Ionization

The process through which radiation interacts with orbital electrons, causing electrons to be ejected from the atom and creating negatively charged electrons and positively charged atoms.

Ions

Charged particles, specifically the negatively charged free electrons and positively charged atoms, produced through the process of ionization.

DNA

The molecule containing the genetic code that controls the operation of each cell and is considered the most important molecule in the body regarding radiation damage.

Deterministic effects

Also known as tissue reactions, these are outcomes such as cell death resulting from unrepaired DNA damage.

Stochastic effects

Radiation-induced outcomes such as cell mutation and cancer that result from unrepaired DNA damage.

Target theory

The concept stating that adverse radiation effects are only observed when sensitive target molecules, specifically the DNA, are affected.

Direct action

An uncommon mechanism of damage where an X-ray photon itself or a free electron interacts directly with the DNA molecule, which represents only $1\%$ of the cell's mass.

Indirect action

The most common cause of DNA damage where radiation interacts with water in the cell (nearly $80\%$ of cell mass), creating ions and free radicals that then harm the DNA.

Radiolysis

The ionization of water where the molecule breaks apart into a negatively charged hydroxyl ion and a positively charged hydrogen ion.

Base pair lesions

The most common type of DNA damage caused by radiation, consisting of small lesions that are easily repaired by the cell.

Single strand breaks

A common effect of radiation on DNA that is usually repaired by the cell without any negative effects.

Double strand breaks

The least common but most significant DNA lesion where the strand breaks completely apart, often leading to cell death or carcinogenesis.