BIO 1000 Lecture Notes - Lecture 14: Tight Junction, Extracellular Fluid, Middle Lamella
4 Mar 2017
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Document Summary
The cell wall, found in prokaryotes, fungi, and some protists, has multiple functions. In plants, the cell wall protects the cell, maintains its shape, and prevents excessive uptake of water. It also supports the plant against the force of gravity. The thickness and chemical composition of cell walls differs from species to species and among cell types within a plant. The basic design consists of microfibrils of cellulose embedded in a matrix of proteins and other polysaccharides. This is the basic design of steel-reinforced concrete or fiberglass. A mature cell wall consists of a primary cell wall, a middle lamella with sticky polysaccharides that holds cells together, and layers of secondary cell wall. Plant cell walls are perforated by channels between adjacent cells called plasmodesmata. The extracellular matrix (ecm) of animal cells functions in support, adhesion, movement, and regulation. Though lacking cell walls, animal cells do have an elaborate extracellular matrix (ecm).
