What is the matrix composed of?

• A. Fibrous proteins and ground substance
• B. Nucleic acids and minerals
• C. Water and electrolytes
• D. Carbohydrates and lipids

Answer: (A)

Think about what makes up the extracellular framework that surrounds cells in connective tissue. The matrix is built from two main parts: fibrous proteins and ground substance. The fibrous proteins, especially collagen, provide strength and structure, while elastin and reticular fibers add elasticity and support. The ground substance is a gel-like material rich in proteoglycans, glycosaminoglycans, and glycoproteins that fills spaces, cushions tissues, and allows nutrients and signals to diffuse to cells. Water and electrolytes are present within this space and support its function, but they don’t define the matrix itself. Nucleic acids and minerals, or carbohydrates and lipids, don’t describe the ECM’s fundamental composition. So the combination of fibrous proteins and ground substance best describes the matrix.