Enzymes are _______.

• A. energy storage molecules
• B. genetic materials that store information
• C. structural components of cell membranes
• D. biological catalysts that speed up chemical reactions

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the role of enzymes in biological systems. Enzymes are specialized proteins that act as catalysts, meaning they speed up chemical reactions without being consumed in the process.
2. Step 2: Eliminate the incorrect options by analyzing their definitions. For example, energy storage molecules (like carbohydrates and lipids) store energy, but they do not catalyze reactions. Genetic materials (like DNA and RNA) store information, but they are not involved in speeding up reactions.
3. Step 3: Consider the structural components of cell membranes. These are primarily phospholipids, cholesterol, and proteins, but enzymes are not classified as structural components of membranes.
4. Step 4: Focus on the correct definition of enzymes. They are biological catalysts that lower the activation energy required for chemical reactions, allowing the reactions to occur more efficiently and rapidly.
5. Step 5: Conclude that the correct answer is: biological catalysts that speed up chemical reactions, as this aligns with the fundamental role of enzymes in biology.