Module 2.5: Cell-to-Cell Adhesions Flashcards
What are the cells of tissues, organs, etc. held together by
 extra cellular matrix act as biological glue, cell adhesion molecules (CAM) ie: cadherin) in the plasma membrane have a loop and hook shape, and by specialized cell junctions
What is ECM secreted by, and what is it
Secreted by fibroblasts, it contains fibrous proteins, gel , and complex carbohydrates (interstitial fluid?)
What are the three fibres found in extra cellular matrix
Collagen, elastin, and fibronectin
Describe collagen
Cable-like or sheets, contributes to tensile strength. Vitamin C deficiency which leads to scurvy causes these fibres to not properly form
Describe elastin fibres
Rubber like, for stretch and recoil
Describe fibronectin
Promote cell adhesion and hold in place. Reduced amount found in cancerous cells which is why metastasizing occurs
What does extra cellular matrix influence for cells
Cell growth and differentiation. Only circulating blood cells survive and function without attaching to extracellular matrix
What are the three types of specialized cell junctions
Desmosomes, tight junctions, and gap junctions
Describe desmosomes
Plaque on the inner surface of adjacent cells are connected by strong glycoprotein (intermediate) filaments. These span the intercellular space, contain cadherons (what actually attach the cells), and attach to the plaque. No direct contact between cells.
Where do we find desmosome junctions and why
Present were considerable stretching occurs like in skin, heart, and uterus. Resist being pulled apart and has tensile strength as it forms a continuous network spanning many cells. Keratin involved
Describe tight junctions
Points of direct contact seal passageway between two cells. Mainly epithelial sheets. Highly selective barriers so passage takes place through sells not between them. Lateral edges of cells joined in a tight seal by kiss sites. Direct fusion of junctional proteins on outer surfaces of interacting plasma membranes
What is the use of tight junctions
To separate two very different substances, for example undigested food and enzymes from blood
Describe gap junctions
Connexions in adjacent cells form channels through which small molecules and ions may pass without entering extra cellular fluid. Six proteins subunits arranged in hollow tubes, with one tube from each connecting cell sticking out so they meet.
What is the role of gap junctions
Communication between cells. They allow movement of ions through cells which transmits electrical activity which result in contraction of a muscle. Found in cardiac and smooth muscle cells mostly, but also some non-muscle cells for passages small nutrients and for coordinating cooperative cell activity
