**Core Concept**
Vitamin E is a fat-soluble antioxidant vitamin that plays a crucial role in protecting cells from oxidative damage. It functions by scavenging free radicals and terminating the chain reaction of lipid peroxidation, thereby preserving the integrity of cell membranes.

**Why the Correct Answer is Right**
Vitamin E acts as a chain-breaking antioxidant, preventing the propagation of lipid peroxidation in cell membranes. This is achieved through its ability to donate a hydrogen atom to lipid radicals, thereby converting them into more stable lipid alcohols. The vitamin E radical that forms is then recycled back to its reduced form by other antioxidants, such as vitamin C. This mechanism is essential for maintaining the structural and functional integrity of cell membranes.

**Why Each Wrong Option is Incorrect**
**Option A:**
Vitamin E is not primarily involved in the regulation of blood pressure. While it may have some indirect effects on cardiovascular health, its main function is as an antioxidant.

**Option B:**
Vitamin E does not play a significant role in the metabolism of fatty acids. Its primary function is to protect cell membranes from oxidative damage, rather than participating in fatty acid oxidation or synthesis.

**Option C:**
Vitamin E is not directly involved in the regulation of gene expression. While it may have some indirect effects on cellular signaling pathways, its primary function is as an antioxidant.

**Clinical Pearl / High-Yield Fact**
It's essential to note that excessive intake of vitamin E can be toxic, leading to symptoms such as headache, dizziness, and fatigue. The recommended daily intake of vitamin E is typically around 15 mg/day, and intakes above this level should be avoided.

**Correct Answer:** D.