Cell walls in plants are primarily composed of which substance?

• A. Chitin
• B. Lignin
• C. Cellulose
• D. Protein

Answer: (C)

Plant cell walls get their strength mainly from cellulose, a long-chain carbohydrate. Cellulose is made of glucose units linked together in beta-1,4 bonds, forming strong fibers called microfibrils. These microfibrils weave through a matrix of other molecules to create a sturdy framework that supports the cell, helps maintain its shape, and resists the pressure from water inside the cell. In the wall, cellulose works with other polysaccharides like hemicellulose and pectin to build a durable yet flexible structure. Chitin is found in fungal cell walls and some arthropods, not in most plant walls. Lignin provides extra stiffness and waterproofing in woody tissues, but it isn’t the primary component of the typical plant cell wall. Proteins are present and play roles in wall remodeling and cross-linking, but they don’t form the main scaffold.