How does cellular metabolism affect radiosensitivity?

• A. Lower metabolic activity increases cell radiosensitivity.
• B. Metabolism does not affect radiosensitivity.
• C. Higher metabolic activity increases cell radiosensitivity.
• D. Metabolic rate only affects repair time, not sensitivity.

Answer: (C)

High metabolic activity makes cells more radiosensitive because metabolism drives oxygen use and the production of reactive oxygen species when radiation hits. Ionizing radiation creates free radicals from water, and the presence of oxygen "fixes" much of this damage, turning initial lesions into permanent, lethal DNA breaks. Cells that are actively metabolizing tend to be well-oxygenated, so there’s more oxygen available to enhance this damage. In contrast, when metabolism is low or tissues are hypoxic, there’s less oxygen to fix the damage, making cells more radioresistant. So the more metabolically active the cell, the greater the expected radiosensitivity due to the oxygen-dependent enhancement of radiation-induced damage.