Final answer:
Plant cell walls are made up of carbohydrates, specifically cellulose, which provides structural support to the cell wall.
Step-by-step explanation:
The macromolecules that make up plant cell walls are carbohydrates. The chief component of plant cell walls is cellulose, which is a polysaccharide made up of long chains of glucose units. Cellulose provides structural support to the plant cell wall.