Which macromolecule forms the foundation for the structure and activities of living cells?

• A. Carbohydrates
• B. Nucleic acids
• C. Proteins
• D. Lipids

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the role of macromolecules in living cells. Macromolecules are large molecules essential for life, including carbohydrates, nucleic acids, proteins, and lipids. Each has distinct functions in cellular structure and activity.
2. Step 2: Analyze the structural role of proteins. Proteins are composed of amino acids linked by peptide bonds, forming complex three-dimensional structures. These structures are crucial for maintaining cell shape, forming cytoskeletal elements, and enabling cellular movement.
3. Step 3: Examine the functional role of proteins. Proteins act as enzymes to catalyze biochemical reactions, transport molecules across membranes, and regulate cellular processes through signaling and gene expression.
4. Step 4: Compare proteins to other macromolecules. While carbohydrates provide energy, nucleic acids store genetic information, and lipids form membranes, proteins uniquely combine structural and functional roles, making them foundational to cellular activities.
5. Step 5: Conclude that proteins are the correct answer based on their dual role in structure and function, which is essential for the foundation of living cells.