Lecture 5 - Specialized Junctions.docx

**Lecture 5: Cell to Cell Adhesions** Cell to Cell Adhesions & Junction Types **Cell to Cell Adhesions** - Plasma membrane participate in Cell - Cell adhesions: the holding together / adhering to each other. - 3 Different ways cells ar held together - **Cell Adhesion Molecules (CA...

**Lecture 5: Cell to Cell Adhesions** Cell to Cell Adhesions & Junction Types **Cell to Cell Adhesions** - Plasma membrane participate in Cell - Cell adhesions: the holding together / adhering to each other. - 3 Different ways cells ar held together - **Cell Adhesion Molecules (CAMs)** - Membrane proteins that allow cells to hold onto each other - Provide some tissue cohesion as they "velcro" adjacent cells together. - **Extracellular Matrix** - (Extracellular) not inside the cell - Intricate network of fibrous proteins surrounded by interstitial fluid (watery, gel-like substance) composed of complex carbohydrates. - Interstitial Fluid: provides pathway for diffusion of nutrients, waste, and other water-soluble traffic between blood and tissue cells. - Extracellular Matrix Protein - ECM is abundant in Connective tissue, not in epithelial - Fibroblasts: Responsible for making most of the cells (collagen, elastin, fibronectin) in the ECM. - Collagen 1. Description: Cable like fibers 2. Function: Tensile strength (allows cells to not be ripped apart)(integrity of tissue) 3. Most abundant protein in body; half of body protein by weight - Elastin 4. Description: Rubber like protein fibers 5. Function: Stretching and recoil - Fibronectin 6. Description: "function as biological glue" 7. Function: Holds cell in position (promotes cell adhesion) 8. Key Point: Reduced levels relate to tumor metastasis - **Specialized Cell Junctions** - **Desmosomes** (adhering junctions) - additional layer of **STRENGTH** - **Function**: Anchor together two adjacent, non-touching cells - **Facts:** 1. Strongest cell to cell connection 2. Most abundant, can stretch - **Location**: Heart, Skin, Uterus - Cytoplasmic thickening plaque + keratin filament (strong protein) are two structures that make the cell - cell adhesion more rigid (Desmosomes) - **Tight Junctions** (impermeable junctions) - physical removal of space, sowing cells together - **Function:** Adjacent cells binds together to seal off passageway between. - **Location:** found in sheets of epithelial tissue that cover internal cavities 1. Digestive tract - **Facts**: Crohn's disease, IBS, - barrier not intact - **Gap Junctions** (communicating junctions) - forming gap between two cells for better communication. - **Description:** A gap between adjacent cells, linked by small, connecting tunnels. 1. Group of proteins called - **Function:** Allow for ions and small water soluble particles to pass, not large molecules - **Location:** Cardiac and Smooth Muscle - **Use Case:** When a process needs to happen at once, synchronized. (E.g., Heart beat)