✅ Correct Answer: Lipids ✔️

Rationale:

Cholesterol is classified as a lipid, specifically a steroid, which is a subgroup of lipids. Lipids are a broad class of biological macromolecules that are hydrophobic (insoluble in water) and include:

Fats and oils (energy storage)
Phospholipids (cell membranes)
Steroids (cholesterol, hormones)

Cholesterol’s Functions:

Essential component of cell membranes, regulating fluidity and stability
Precursor for steroid hormones (e.g., estrogen, testosterone, cortisol)
Used to synthesize bile acids for digestion
Involved in vitamin D production

Why the Other Choices Are Incorrect:

❌ Fatty Acids – Fatty acids are the building blocks of many lipids but are not the same as cholesterol. Cholesterol has a complex, ringed structure, whereas fatty acids have long hydrocarbon chains.

❌ Phospholipid – Phospholipids consist of a glycerol backbone, two fatty acids, and a phosphate group, forming cell membranes. Cholesterol lacks this structure but integrates into phospholipid bilayers to help regulate membrane fluidity.

❌ Triglyceride – Triglycerides consist of glycerol and three fatty acid chains and serve as the body's primary energy storage molecules. Cholesterol does not contain glycerol and is not an energy-storage lipid.

HESI A2 Exam Prep

Biochemistry (Macromolecules, Enzymes)

Rationale