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Lecture 16-17: Tissues and Organs/ Cytoskeleton (Cell Junctions (Tight…
Lecture 16-17: Tissues and Organs/ Cytoskeleton
Two or more tissues form an organ
Cytoskeleton
Intermediate Filaments
Only in animals
Rope
Keratin
Form sturdy mesh
Microfilaments
Helical polymers of actin monomers
Actin in filaments is called F-actin
Give shape to animal cells
Can take on different shapes (stress fibers, lamellopodia, filopodia), to change shape & enable migration
Actin microfilaments associate with myosin to move vesicles & cause muscle contraction
Microtubules
#
Hollow polymers of tubulin dimers
Dynamic instability
Dynein (outward) and kinesin (in) transport substances
α & β- tubulin two proteins that make up filaments
Grow from centrosome
Cilia & Flagella driven by microtubules
Cell Junctions
Cadherins join cytoskeleton cell to cell
Integrins anchor cytoskeleton to extracellular matrix
Tight junctions
- prevent passages of substances through spaces between cells- divide plasma membrane into apical and basolateral regions
Claudins, Occludins
Adherens Junctions
- form belt, made of cadherins
Microfilaments
Desmosomes
: button-like points of adhesion; made of cadherins
Intermediate filaments
Hemidesmosomes
: Made of integrins; connect cytoskeleton to extracellular matrix
Actin & intermediate filaments
Epithelial tissue cells are tightly joined in a sheet- apical to basal orientation
Noncovalent interactions; Structural support