Video Transcript
Which of the following is not a reason why large amounts of ionizing radiation may be
harmful to living organisms? (A) Ionizing radiation may inhibit cellular mitosis. (B) Ionizing radiation may reduce the intracellular temperature. (C) Ionizing radiation may trigger cellular apoptosis. (D) Ionizing radiation may have enough energy to break chemical bonds. (E) Ionizing radiation may affect the genetic information carried in cellular
DNA.
Radioactivity is spontaneous emission of radiation from unstable nuclei in atoms. There are two forms of radiation: ionizing radiation and nonionizing radiation. Ionizing radiation carries enough energy to remove electrons from atoms, and
nonionizing radiation does not. Depending on the type of radiation and how long an organism is exposed, multiple
negative effects may occur. These effects are caused because this type of radiation ionizes atoms or
molecules. These ionized atoms and molecules may then damage DNA, proteins, and enzymes, which
are essential for the functioning of the cell. Ionizing radiation may also directly break the chemical bonds in molecules. Knowing this allows us to eliminate answer choice (D). However, let’s spend some time discussing the other answer choices in more
detail.
In answer choice (A), we are told that ionizing radiation may inhibit or stop
cellular mitosis. Mitosis is the process of cell division, during which DNA is copied and a single cell
splits into two daughter cells. If DNA or the enzymes and proteins involved in mitosis are damaged, this could
interfere with mitosis or stop it altogether. Since this is a harmful effect of ionizing radiation, we can eliminate answer choice
(A).
Answer choice (C) mentions another biological process called apoptosis, which is cell
death. If a cell is exposed to too much ionizing radiation, it may not be able to repair
itself and could die. Therefore, we can also eliminate answer choice (C).
Now let’s take a look at answer choice (E). We already know that ionizing radiation can damage DNA. Therefore, it is reasonable to conclude that some types of damage to DNA may be
passed on to the offspring of organisms. So we can also eliminate answer choice (E).
This leaves only answer choice (B). We know that ionizing radiation causes damage by removing electrons from atoms and
molecules and breaking chemical bonds. Forms of nonionizing radiation such as infrared and microwaves can raise the
temperature of cells. And we’re probably quite familiar with how microwave ovens can be used to heat
food. We can see now that it’s pretty unlikely that ionizing radiation is going to reduce
or lower the temperature of cells.
In conclusion, the statement that is not a reason why large amounts of ionizing
radiation may be harmful to living organisms is answer choice (B). Ionizing radiation may reduce the intracellular temperature.
