In an experiment, metabolically active cells are subjected to radiant energy in the form of x-rays. This results in cell injury caused by hydrolysis of water. Which of the following intracellular enzymes helps to protect the cells from this type of injury?
**Core Concept**
The question requires understanding of cellular defense mechanisms against radiations. Hydrolysis of water leads to the formation of highly reactive free radicals, which cause oxidative stress and cell injury. Cells employ antioxidant enzymes to neutralize these free radicals.
**Why the Correct Answer is Right**
The enzyme superoxide dismutase (SOD) plays a crucial role in protecting cells from oxidative stress caused by radiations. SOD catalyzes the dismutation of superoxide (O2−) radical into oxygen and hydrogen peroxide (H2O2). This process helps to reduce the concentration of free radicals and prevent lipid peroxidation, DNA damage, and cell injury. SOD is a metalloenzyme that contains copper and zinc ions, which facilitate the catalytic activity.
**Why Each Wrong Option is Incorrect**
**Option A:** Catalase is an enzyme involved in the breakdown of hydrogen peroxide into water and oxygen. While catalase does help to reduce oxidative stress, it is not directly involved in protecting cells from radiation-induced hydrolysis of water.
**Option B:** Glutathione peroxidase is an enzyme that reduces lipid hydroperoxides to their corresponding alcohols and reduces free hydrogen peroxide to water. Although it plays a role in antioxidant defense, it is not the primary enzyme responsible for protecting cells from radiation-induced cell injury.
**Option C:** This option is blank and needs to be filled with the actual incorrect option.
**Clinical Pearl / High-Yield Fact**
Superoxide dismutase (SOD) is an essential enzyme in maintaining cellular redox balance. It is often used as a marker of cellular oxidative stress and is involved in various diseases, including cancer, atherosclerosis, and neurodegenerative disorders.
**Correct Answer:** C. Superoxide dismutase (SOD)