Cellulose and Pectic Polysaccharides

New plant cells have a primary cell wall and middle lamella, comprising cellulose fibers embedded in a gel-like matrix containing polysaccharides and proteins.

Cellulose is a long, linear chain of glucose. Around sixteen cellulose molecules are connected in parallel by hydrogen bonds, forming rod-like microfibrils that impart rigidity and resist tensile forces.

Branched polysaccharides, such as hemicellulose, cross-link microfibrils into a structural network that allows expansion during cell growth.

The cross-linked cellulose layers are suspended in a pectin matrix.

Pectins are polysaccharides containing negatively charged galacturonic acid units surrounded by cations and water molecules. Calcium ions crosslink pectins into a semirigid gel that cements the walls of adjacent cells.

As a plant cell matures, a secondary cell wall can form between the primary cell wall and the plasma membrane. It contains hardening polymers such as lignin that provide the protection and support required for water movement.