BIOC 212 Lecture Notes - Lecture 21: Glucose Transporter, Cell Membrane, Symporter
29 May 2018
School
Department
Course
Professor
Cell Junctions & Cell Adhesion I
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Cell Junctions
• How are cells held together, how do they work together?
o Direct binding
• Cell-cell junctions
• Cell adhesion
o Cell surface receptors
• Bind cells to matrix
o Extracellular matrix
• Complex network of secreted macromolecules
• Many functions, but one of the most important ones is supporting
framework
Epithelial & Connective Tissue
• Cross-sectional view of intestinal wall
• Tube-like organ constructed from
o Epithelial tissue (red)
• Epithelial cells stick tightly together
o Connective tissue (green)
• Proteins, collagen, glycoproteins
• Fibroblast cells --> do not form tight cell layer, distributed throughout
the connective tissue
• Have some connections, but not as much as epithelial cells
o Muscle tissue (yellow)
• Important for constriction of gut or other tissues
• Each tissue organized assembly of cells held together by cell-cell adhesions, cell-
extracellular matrix adhesions, or both
• Some major tissue types in vertebrates;
o Nerve
o Blood
o Muscle
o Lymphoid
o Epithelial
o Connective
• Compare connective tissues with epithelial cells
Classification of Cell Junctions
• Occluding junctions: seal cells together in an epithelium, no leaking from one
side to the other
o Tight junctions found in epithelial cell layer in gut and other tissues
• Only found in vertebrates
Document Summary
Classification of cell junctions: occluding junctions: seal cells together in an epithelium, no leaking from one side to the other, tight junctions found in epithelial cell layer in gut and other tissues, only found in vertebrates, septate junctions. Insects & other invertebrates: anchoring junctions: mechanically attach cells to neighbors in the ecm, 3 fiber systems; main elements of intracellular cytoskeleton, actin filaments. Intermediate filaments: microtubules --> do not play role in this scenario. In terms of anchoring junctions, only actin and intermediate filaments play a role in connecting to the cytoskeleton: actin filaments, adherens junctions (cell to cell, focal adhesions (cell to ecm) Intermediate filaments: desmosomes (act from cell to cell, hemidesmosome (cell to ecm, communicating junctions: mediate the passage of signals from one to the next, gap junctions, allow exchange of molecules between cells, chemical synapses, plasmodesmata (plants) Tight junctions in transcellular transport: physiological function in which tight junctions are important.
