**Core Concept**
Vitamin C, also known as ascorbic acid, plays a crucial role in various physiological processes, but its primary function is related to its antioxidant properties. As a water-soluble vitamin, Vitamin C is essential for maintaining the integrity of collagen, iron absorption, and immune function.

**Why the Correct Answer is Right**
Vitamin C acts as a powerful antioxidant by scavenging free radicals and neutralizing reactive oxygen species (ROS). This is achieved through its ability to donate electrons, thereby preventing oxidative damage to cellular components, including DNA, proteins, and lipids. The antioxidant properties of Vitamin C are mediated by its interaction with enzymes involved in the detoxification of ROS, such as superoxide dismutase and glutathione peroxidase. This helps to maintain the balance between the production of free radicals and the body's antioxidant defenses.

**Why Each Wrong Option is Incorrect**
**Option A:** Vitamin C does not serve as a coenzyme for energy metabolism; this function is primarily associated with vitamins like NAD and FAD, which are involved in redox reactions.
**Option B:** Regulation of lipid synthesis is not a primary function of Vitamin C; this process is primarily regulated by hormones and enzymes such as HMG-CoA reductase.
**Option D:** Inhibition of cell growth is not a known function of Vitamin C; in fact, Vitamin C is essential for the growth and development of cells.

**Clinical Pearl / High-Yield Fact**
Vitamin C deficiency, also known as scurvy, can lead to impaired collagen synthesis, leading to symptoms such as fatigue, malaise, and poor wound healing.

**✓ Correct Answer: C. Involvement as antioxidant**