Final answer:
Free radicals cause cellular injury through the process of cell membrane damage. They are highly reactive molecules that can oxidize other molecules and lead to oxidative stress, DNA mutations, and various diseases.
Step-by-step explanation:
Free radicals are unstable molecules that cause cellular injury through the process of cell membrane damage. Free radicals are highly reactive because they contain free unpaired electrons, which can easily oxidize other molecules in the cell and result in damage or cell death. Examples of cellular damage caused by free radicals include oxidative stress, DNA mutations, and diseases such as cancer and cardiovascular disorders.