What substance do eukaryotic cell walls primarily consist of?

Eukaryotic cell walls primarily consist of cellulose, particularly in plants, which are a major group of eukaryotes. Cellulose is a complex carbohydrate, or polysaccharide, that provides structural support to plant cells. It is composed of long chains of glucose units linked together, forming a rigid structure that helps maintain the shape of the cell and offers protection against external factors.

In addition to plants, some other eukaryotes, such as algae, also have cell walls made of cellulose or similar substances, reinforcing the idea that cellulose is a key component of eukaryotic cell walls.

It's important to note that while other substances like chitin also play a role in cell walls, particularly in fungi and some protists, cellulose is the primary constituent in the context of eukaryotes, especially in plants. In contrast, peptidoglycan is specific to bacterial cell walls, while proteins are not a primary structural element of eukaryotic cell walls.