Which of the following pigments are involved in free radical injury?
**Core Concept**
Free radical injury is a type of oxidative stress that occurs due to the uncontrolled production of reactive oxygen species (ROS), leading to cellular damage. This process involves the interaction of various cellular components, including lipids, proteins, and DNA, with ROS.
**Why the Correct Answer is Right**
Melanin and bilirubin are antioxidants that protect cells from oxidative damage by neutralizing free radicals. Melanin, in particular, has been shown to scavenge ROS and protect against oxidative stress in various cell types. On the other hand, lipofuscin is a type of waste material that accumulates in cells over time and is associated with oxidative stress and cellular aging. It is not an antioxidant.
**Why Each Wrong Option is Incorrect**
* **Option A:** Lipofuscin is not an antioxidant but rather a marker of cellular aging and oxidative stress.
* **Option B:** Bilirubin is an antioxidant that protects against oxidative stress, whereas lipofuscin is not.
* **Option D:** Melanin is an antioxidant that neutralizes free radicals, whereas lipofuscin is a waste material that accumulates in cells.
**Clinical Pearl / High-Yield Fact**
Lipofuscin accumulation is a marker of cellular aging and oxidative stress, and it can be reduced by antioxidants such as melatonin and vitamin E.
**Correct Answer:** C. Lipofuscin.