**Core Concept**
Phospholipids are a class of lipids that play a crucial role in the structure and function of cell membranes. They are amphipathic molecules, containing both hydrophobic and hydrophilic regions, which allows them to interact with both water and non-polar molecules.

**Why the Correct Answer is Right**
Phospholipids are composed of a glycerol backbone linked to two fatty acid chains and a phosphate group. The phosphate group is linked to a polar head group, which is typically an alcohol or a sugar molecule. This unique structure allows phospholipids to form a bilayer in aqueous environments, with the hydrophobic fatty acid chains facing inward and the hydrophilic phosphate groups facing outward. This bilayer structure is essential for maintaining the integrity of cell membranes and regulating the movement of molecules across the membrane.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is likely incorrect because it does not accurately describe the composition or function of phospholipids.
* **Option B:** This option may be incorrect because it does not specifically mention the amphipathic nature of phospholipids, which is a key characteristic of these molecules.
* **Option C:** This option is likely incorrect because it does not accurately describe the role of phospholipids in cell membranes.

**Clinical Pearl / High-Yield Fact**
Phospholipids are an essential component of cell membranes and play a critical role in maintaining membrane integrity and regulating the movement of molecules across the membrane. This is particularly important in the context of diseases such as atherosclerosis, where phospholipid metabolism is disrupted.

**Correct Answer:** D.