Which of the following is an example of a molecule from the class of lipids called steroids?

• A. Phosphatidylcholine
• B. Cholesterol
• C. Triglyceride
• D. Oleic acid

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the classification of lipids. Lipids are a diverse group of biological molecules that include fats, oils, phospholipids, and steroids. Steroids are a specific class of lipids characterized by a structure of four fused carbon rings.
2. Step 2: Analyze the options provided. Phosphatidylcholine is a phospholipid, triglycerides are fats composed of glycerol and three fatty acids, and oleic acid is a monounsaturated fatty acid. Cholesterol, however, is a steroid due to its characteristic four-ring structure.
3. Step 3: Recall the biological role of steroids. Steroids, such as cholesterol, are involved in cell membrane structure and serve as precursors for steroid hormones like estrogen and testosterone.
4. Step 4: Compare the molecular structures. Cholesterol has the defining four-ring structure of steroids, while the other options do not share this structural feature.
5. Step 5: Conclude that the correct answer is cholesterol, as it fits the definition and structural characteristics of a steroid lipid.