Extracellular Matrix

Supporting structure for cells scaffolding for tissues Synthesized by cells involved in the ECM tissue: highly variable depending on the function Connective tissue: High ECM component and low number of cells Epithelial tissue: High number of cells and low ECM component ECM is synthesized by fibroblast cells which are relatively non-specialized connective tissue cells

Polysaccharide Component Glycosaminoglycans (GAG's): repeating disaccharide chains One amino sugar (EX: N-acetylglucosamine) and one acidic sugar (EX: iduronic acid) has a net negative charge chondroitin - prevalent in cartilage attracts a positively charged ions (sodium) which also attracts water to maintain moist tissue do not fold: stiff and inflexible providing mechanical support GAG's can be assembled into proteoglycans protein core with GAG's attached at ser/thr residues via tri-saccharide linker proteoglycans can aggregate onto a hyaluronic acid core --> large molecular weight

Protein Component Collagen: three alpha helices wound together (collagen triple helix) abundant in: gly, lys, pro, OH-proline Many types of collagen I, II, III are fibrous and rope-like IV is net-like ex: basal lamina Collagen Synthesis Chain synthesis Hydroxylation of selected proline residues Glycosylation occurs as well Folding of the triple helix contains amino acid residues on ends ("pro" sequences) which prevent the formation of fibrils inside the cell Forms microfibrils once excreted by the cells Elastin: structural protein good for resilience (bouncy) Fibronectin: adhesive function - connects cells to the ECM Basal lamina: thin mat of ECM between epithelial tissue and underlying tissue Collagen type IV Perlecan Laminin Entactin