BIO 311D Study Guide - Adrenal Medulla, Diabetes Mellitus Type 2, Tight Junction
Document Summary
Major characteristics- lack cell walls, no central vacuole, no chloroplasts, and have an extracellular matrix. Distinguish tight junctions, gap junctions, desmosomes (anchoring) and tell the function of each. tight junctions- the plasma membrane of neighboring cells are very tightly pressed against each other, bound together by specific proteins. Forming continuous seals around the cells, tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells. Gap junctions consist of membrane proteins that surround a pore through which ions, sugars, amino acids, and other small molecules may pass. Gap junctions are necessary for communication between cells in many types of tissues, such as heart muscle, and in animal embryos. desmosomes (anchoring junctions)- function like rivets, fastening cells together into strong sheets. Intermediate filaments made of sturdy keratin proteins anchor desmosomes into the cytoplasm. Desmosomes attach muscle cells to each other in a muscle. Some muscle tears involve the rupture of desmosomes.
