BIOL130 Lecture Notes - Lecture 11: Chondroitin Sulfate, Ultimate Tensile Strength, Microfibril
Document Summary
Extremely rare for plasma membrane to be the only structure surrounding a cell. Cell wall in bacteria, algae, fungi, plants. Cross linked network of filaments (resists stretching and straining forces, steel rods in a building) Semi-solid, gelatinous matrix (polysaccharides/proteins = resist compression & are concrete) Collagen fibers and salts secreted by osteocytes as part of ecm. Pectin in outer layers (primary cell walls; still growing) Cellulose in secondary cell walls (stopped growing) Plants are sedentary (inactive), tissues are fairly rigid, cells are weak & fragile if separated from their walls (protoplasts) Cell wall is an ecm secreted by plant cell. Primary cell wall: secreted as cells are growing, relatively thin (pectin, cellulose formed by microfibril networks of pectin), all cells have this wall. Hydrophilic & withstands compression by absorbing water. Pectins made in rough er, processed in golgi, secreted. Cellulose made at plasma membrane by protein complexes. Primary cell wall contains cellulose synthase enzymes.