CELL TO CEL ADHENSION.pdf

CELL TO CEL ADHENSION Friday, September 15, 2023 9:55 AM CELL TO CELL ADHENSIONS → Plasma membranes also participate in cell-to-cell adhesion → Cells are held together by three different means: ○ Cell Adhesion Molecules (CAMs) -> anchored to the membrane ○ The Extracellul...

CELL TO CEL ADHENSION Friday, September 15, 2023 9:55 AM CELL TO CELL ADHENSIONS → Plasma membranes also participate in cell-to-cell adhesion → Cells are held together by three different means: ○ Cell Adhesion Molecules (CAMs) -> anchored to the membrane ○ The Extracellular Molecules (ECMs) ○ Specialized cell junctions EXTRACELLUALR MATRIX → The ECM is an intricate network of fibrous proteins embedded in a watery, gel-like substance (A.k.a. interstitial fluid) composed of complex carbohydrates ○ The interstitial fluid provides a pathway for diffusion of nutrients, wastes, and other water-soluble traffic between the blood and tissue cells ○ It is the space and fluid between cells in the tissue ○ ECM is located on the outside of all cells THE 3 TYPES OF EXTRACELLULAR PROTEIN FIBERS → Collagen ○ Forms cable-like fibres ○ Tensile strength (most abundant protein in the body) § The strongest fiber we have ○ About 1/2 of total body protein by weight ○ Found in every cell ○ Can be found in skin, muscle, and bone and tissue ○ The type of tissue that produces scars → Elastin ○ Rubber-like protein fiber ○ Stretching and recoiling ○ Can be found in the lungs and heart → Fibronectin ○ Promotes cell adhesion ○ Holds cells in position (reduced levels are linked to tumor metastasis) § Beneficial to cancer cells = prevents them from escaping and multiplying → They serve as a biological glue for cells → Scant in epithelial tissue; abundant in connective tissue → Secreted by fibroblasts ○ Special cell type that makes these protein fibers SPECIALIZED CELL JUNCTIONS → CAMs provide some tissue cohesion as they "Velcro" adjacent cells together ○ More useful in signaling and communication → Cells are directly linked by one of three types of specialized cell junctions: → Desmosomes (adhering junctions) ○ Strongest cell to cell conjunction / connections ○ Most abundant in tissues that are subject to considerable stretching § Found in the skin, liver, uterus and heart ○ Act like "spot rivets" that anchor together two adjacent but non-touching cells Picture description: ○ Each cell has a cytoplasm thickening plaque that has intracellular keratin filaments attached to them from the INSIDE ○ In-between cells are intercellular filaments that connect together ○ Desmosomes is the unit of 2 cells' intercellular filaments joined → Tight Junctions ( impermeable junctions) ○ Adjacent cells firmly bind together at points of contact to seal off the passageway between the two cells ○ Found primarily in sheets of epithelial tissue such as those that cover the body and line internal cavities ○ Impermeable barrier ○ Cells touch ○ This gives the cell membrane full control of what can pass through into the cell Picture description: ○ Epithelial sheet lining the digestive tract separates the food and potent digestive juices within the inner cavity (lumen) from the blood vessels on the other side ○ There are strands of junctional proteins that hold the cells together - Think of it as the walls being sewed together Picture description: ○ A gap exist between adjacent cells, which are linked by small, connecting tunnels (formed by connexons) → Gap junctions ( communicating junctions) ○ Acts as a tunnel for 2 cells or a series of cells that are around each other ○ Connects cellular membranes but they do not touch ○ Allows for faster communication ○ Communicating junctions (permits small, water soluble particles to pass between the connected cells but precludes passage of large molecules) § Allows small ions, but not lipids, glucose, or anything big ○ Abundant in cardiac muscle and smooth muscle - allow movement of ions to transmit electrical activity -> synchronized contraction of a whole muscle mass)