BMS 300 EXAM 2 (A+ GRADED)

How are cells connected to each other and the extra-cellular matrix? correct answers -gap junctions -tight junctions -anchorning junctions How do we classify epithelial tissue? correct answers -cell shape -number of layers What is a Gap junction? correct answers Mediates cell to cell communication, Aggregates of intercellular channels that permit direct cell to cell transfer of ions and small molecules, What does a gap junction do? correct answers -connects to the cytoplasm in adjacent cells -couple cells both electrically and metabolically -low resistant ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues Gap junction mediation correct answers By changes or signals (pH, Ca2+) (neurotransmitters) Gap junction- connexons correct answers -turnover of connexons is rapid -multiple isoforms of connexins permit tissue specific gap junctions -different combinations of connexins create channels that differ in permeability and regulation What is a gap junction composed of? correct answers composed of hexamers of medium sized families of integral proteins: connexins in chordates What do tight junctions do? correct answers Hold the cells together and form a near leak proof intercellular seal by the fusion of adjacent cell membranes Claudin correct answers Tight junction, main transmembrane proteins, seal is selectively permeable, protein family has many members Tight junctions and pathology- diseases correct answers -claudins are dysregulated in various cancers -inflammatory bowel diseases, correlated with claudin dysregulation Occludin correct answers Tight junction, second major transmembrane (in between claudin and JAMS) Zonula occludens correct answers Tight junction, large scaffold proteins that provide a structural support , not in the gap, connect the occuludin, claudin, JAMS, to the walls