**Core Concept**
Rafts in the cell membrane are specialized lipid microdomains that play a crucial role in cell signaling, membrane trafficking, and disease processes. These structures are enriched with specific lipids and proteins that facilitate their formation and function.

**Why the Correct Answer is Right**
Rafts are rich in sphingolipids and cholesterol, which are the primary components that contribute to their formation and stability. The hydrophobic tails of the sphingolipids and cholesterol molecules interact with each other, creating a platform for the assembly of signaling molecules and membrane proteins. This organization allows for the efficient transmission of signals and the regulation of membrane trafficking. The presence of sphingolipids and cholesterol in rafts also influences the fluidity and permeability of the cell membrane.

**Why Each Wrong Option is Incorrect**
**Option A:** Saturated fatty acids are not the primary components of rafts, although they may contribute to the membrane's overall lipid composition.
**Option B:** Phosphatidylserine is a phospholipid that is often found in the inner leaflet of the cell membrane, whereas rafts are typically enriched with sphingolipids and cholesterol in the outer leaflet.
**Option C:** Glycolipids, such as GM1, are found in rafts but are not the primary components that define these structures.

**Clinical Pearl / High-Yield Fact**
Rafts play a critical role in the pathogenesis of various diseases, including atherosclerosis, Alzheimer's disease, and cancer. Understanding the composition and function of rafts is essential for the development of targeted therapies and diagnostic tools.

**Correct Answer:** C. Cholesterol