Which of the following is a primary biological role of lipids in living organisms?

• A. They transport oxygen in the blood.
• B. They serve as long-term energy storage molecules.
• C. They directly encode genetic information.
• D. They catalyze biochemical reactions as enzymes.

Answer: (B)

Verified step by step guidance

1. Understand the question: The problem is asking about the primary biological role of lipids in living organisms. Lipids are one of the four major macromolecules in biology, alongside carbohydrates, proteins, and nucleic acids.
2. Review the options provided: The question lists several roles, such as transporting oxygen, encoding genetic information, catalyzing reactions, and serving as long-term energy storage molecules. Evaluate each option based on your knowledge of lipid functions.
3. Recall the primary functions of lipids: Lipids are hydrophobic molecules that play key roles in energy storage, cell membrane structure, and signaling. They are not involved in transporting oxygen (a role of hemoglobin), encoding genetic information (a role of DNA/RNA), or catalyzing reactions (a role of enzymes, which are proteins).
4. Focus on energy storage: Lipids, particularly triglycerides, are well-known for their ability to store energy efficiently. They provide more energy per gram than carbohydrates or proteins, making them ideal for long-term energy storage in organisms.
5. Conclude the correct answer: Based on the analysis, the primary biological role of lipids in living organisms is to serve as long-term energy storage molecules. This aligns with their chemical properties and biological functions.