Which of the following is not true about proteoglycans?

Proteoglycans are intricate macromolecules found in the extracellular matrix, composed of a core protein to which glycosaminoglycan (GAG) chains are attached. These GAG chains are long, linear polysaccharides rather than short and branched structures.

The assertion that they are "mostly short and branched chains" misrepresents the nature of GAGs in proteoglycans. Instead, GAGs like hyaluronic acid and chondroitin sulfate are typically linear and can be very long. This linear arrangement allows proteoglycans to play significant roles in providing structural support, hydration, and facilitating cell signaling within tissues.

The other statements about proteoglycans are accurate: they do indeed comprise a high carbohydrate content—up to 95% of their mass—and the typical length of individual GAG chains can be around 80 sugars. Therefore, acknowledging the properties of the carbohydrate components and chain lengths helps clarify why the characterization of GAGs as "mostly short and branched chains" is not true.