Consider the question. In aerobic organisms the energy needed to fuel biological functions is produced in the mitochondria via the electron transport chain. In addition to energy, reactive oxygen species (ROS) with the potential to cause cellular damage are produced. ROS can damage lipid, DNA, RNA, and proteins, which, in theory, contributes to the physiology of aging.

Answer this question based on the passage: where are reactive oxygen species produced in the body?
What is the step-by-step reasoning process to arrive at the answer: in the mitochondria?
To answer the above question, the relevant sentence is: In addition to energy, reactive oxygen species (ROS) with the potential to cause cellular damage are produced.