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Extracellular Matrix of the Animal Cell. What is the extracellular matrix (ECM)?. Something that is made by virtually all multi-cellular organisms. Elaborate covering outside animal cell membranes, occupying the space between cells. It is composed of:
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What is the extracellular matrix (ECM)? • Something that is made by virtually all multi-cellular organisms. • Elaborate covering outside animal cell membranes, occupying the space between cells. It is composed of: • Collagen, proteoglycans, and fibronectin, which the cell secretes. • Different from the plant extracellular matrix, which is composed of cellulose. • Many ECM components are involved in cell-to-cell interactions.
Components of the ECM • Collagen • Most abundant glycoprotein (about half of the total protein in the body). • Forms strong fibers outside of the cell. • Fibers are embedded in a network made of proteoglycans. • Proteoglycans • Collagen fibers are embedded in a network made from proteoglycans. • Are another class of glycoproteins that consists of a small core protein with many carbohydrate chains covalently attached. • Large complexes can form when hundreds of proteoglycans become non-covalently attached to a single long polysaccharide molecule.
Components (cont.) • Fibronectin • Glycoprotein that attaches the ECM to the cell itself. • Binds to cell surface receptors called integrins, which are built into the plasma membrane of the cell. • Integrins • Cell surface receptor that connects to fibronectin, which attaches to the ECM • Span the membrane and bind on their cytoplasmic side to associated proteins attached to microfilaments of the cytoskeleton. • Transmit’s changes between the ECM and the cytoskeleton – it integrates changes occurring outside and inside the cell.
Fig. 6-30 Polysaccharide molecule Proteoglycan complex Collagen EXTRACELLULAR FLUID Carbo- hydrates Fibronectin Core protein Integrins Proteoglycan molecule Plasma membrane Proteoglycan complex CYTOPLASM Micro- filaments
ECM Effect on Behavior • By communicating with a cell through integrins, the ECM can regulate a cell’s behavior. • ECM can influence the activity of genes in the nucleus. • Speculated that information probably reaches the nucleus by a combination of chemical and mechanical signaling pathways. • Mechanical includes fibronectin, integrins, and microfilaments of the cytoskeleton. • The cytoskeleton may then trigger chemical signaling pathways inside the cell, leading to changes in the proteins being made by the cell and therefore in its function. • The ECM may help coordinate the behavior of all the cells within that tissue. • Direct connections (intercellular junctions) between cells also function in this coordination.