What causes degeneration of mitochondria?

• A. Lack of oxygen
• B. Exposure to oxygen and free radicals
• C. Viral infection
• D. Excess calcium

Answer: (B)

Mitochondrial degeneration is driven most directly by oxidative stress from exposure to oxygen and free radicals. Reactive oxygen species, such as superoxide and hydroxyl radicals, attack mitochondrial lipids, proteins, and mitochondrial DNA. This damages the inner membrane and components of the electron transport chain, disrupts the membrane potential, and leads to swelling, cristae disruption, and impaired ATP production. Lipid peroxidation of membrane lipids like cardiolipin further destabilizes mitochondria, accelerating degeneration. Although oxygen is essential for energy production, excess ROS overwhelm antioxidant defenses (like SOD, catalase, and glutathione) and drive mitochondrial dysfunction. In contrast, while hypoxia, viral effects, or high calcium can impair mitochondria, the most direct cause of degeneration in this context is oxidative damage from oxygen and free radicals.