What carbohydrate provides rigidity to plant cell walls?

Cellulose is the carbohydrate that provides rigidity to plant cell walls. It is a polymer made up of long chains of glucose molecules linked together by beta-1,4-glycosidic bonds. The structure of cellulose allows it to form strong fibers, which contribute to the overall strength and structure of the cell wall in plants. This rigidity is essential for maintaining plant shape, supporting growth, and withstanding external pressure.

While starch serves as an energy storage form in plants, it does not provide structural support. Glycogen, similar to starch but used by animals for energy storage, also does not contribute to cell wall rigidity. Chitin, while structurally similar to cellulose, is found in the exoskeletons of arthropods and the cell walls of fungi, and is not involved in plant cell walls. Thus, cellulose is uniquely suited to fulfill the purpose of providing structural integrity in plants.