Plant cell wall

A rigid extracellular layer surrounding plant cells, built chiefly from cellulose fibers embedded in a matrix of other molecules. It supports cells, resists internal pressure, and helps shape plant tissues.

Cellulose: A structural polysaccharide made of glucose chains that form strong fibers in plant cell walls. Cellulose microfibrils provide the wall’s main tensile strength.
Cellulose synthase: A membrane-associated enzyme complex that polymerizes glucose into cellulose chains and extrudes them outside the cell. Its movement across the membrane lays down cellulose microfibrils.
Wood: The lignified secondary xylem of trees and other woody plants. Wood’s stiffness and durability arise from specialized, lignified cell walls.
Animal extracellular matrix: A network of proteins and polysaccharides outside animal cells that supports tissues and mediates signaling. Unlike the plant wall, this matrix is not a rigid cellulose-based layer.
Hemicellulose: A group of branched polysaccharides that bind cellulose fibers in plant cell walls. Hemicellulose links cellulose microfibrils into a load-bearing network.
Cell expansion: An increase in cell size driven largely by water uptake and yielding of the cell wall. Wall loosening permits turgor pressure to expand growing cells.
Dietary fiber: Indigestible carbohydrate and related plant material that affects digestion and other aspects of health. Cellulose and pectin from plant walls are major dietary fibers.
Bacterial cell wall: A structural layer outside the bacterial plasma membrane, usually built from peptidoglycan. Bacterial walls provide rigidity but have a different principal polymer.
Pectin: A family of acidic polysaccharides found in plant cell walls, especially abundant in the middle lamella. Pectin-rich matrix helps neighboring cells adhere and influences wall porosity.
Turgor pressure: The pressure of a cell’s contents against its surrounding wall, generated by water uptake. The wall withstands turgor while allowing controlled expansion.

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