Extracellular Matrix Flashcards
Bacterial cell walls
-shape (rod vs spiral)
-protect from osmotic pressure
- made of peptidoglycan
Penicilin and bacteria
Penicillin kills bacteria by inhibiting enzyme responsible for making the cross-links
Eukaryotic Cell Walls- (plants)
-made of cellulose (Beta gluc monomers)
- after leaving cell= associate into myofibrils
Euk cell wall (fungi)
- made of chitin
–>made from a glucose derivative
Myofibrils and Pectin
- Myofib interact w/ other sugars and proteins to make the cell wall
-pectin has many neg charged residues, which can trap cations and water molecules creating a gel
ECM
fills space bt cells and binds cells and tissues together
types of ECM
- made from secreted proteins and polysaccharides
- basal lamina
- collagen
- elastin
Basal Lamina
layer of ECM sec by epithelium cells (also surround muscle cells, fat cells, and peripheral nerves)
- abundant in connective tissues
main family of proteins in ECM (Collagens)
- form a triple heliz structure from amino acids secreted from the cell
- further associate to form collagen fibers
Elastin
-important component of ECM (esp connective tissue)
- cross-linked to allow them to stretch and retract
- work in conjunc w/ collagen to give elasticity to the skin
Glycosaminoglycans
(GAGs)
- make a polysaccharide gel that protein fibers are embedded into
- link proteins to for proteoglycans
Adhesion proteins
link the components of the matrix together (ex: collagen and proteoglycans) AND links cell to the matric
ex: fibronectin and laminin
ECM and cell attatchment
- made via integral proteins ex: integrins
-will recognize and bind to specific amino acid sequences found in diff components of the matrix or cytoskeleton
integral proteins
present in focal adhesions and hemidesmosomes
Locomotion steps
- protrusion
- Substrate adhesion
- Traction/cell body movement
protrusion
The leading edge usually shows filopodia and lamellipodia. These extensions probe forward in search of a new substratum contact site.
substrate adhesion
If and when the leading edge encounters an adhesive region of the substratum it will attach, stabilizing the forward extension. The mechanism of attachment involves integral membrane receptors and their coupling to internal cytoskeletal elements.
traction/ cell body movement
Once a new forward contact has been made a mechanism must exist to move the bulk of the cell cytoplasm in that direction. Several activities are believed to contribute.
Selectins
ligands recognized- carbs
stable cell junction- no
integrins
ligand recog- ECM
stable junctions?- focal adhesions and hemidesmosomes
lg superfamily
lig recog: integrijns
stable cell junc? - not usually
cadherins
-other cadherins recog
-cell junc stable? adherens junctions and desmosomes
Loss of Cadherins…
in epithelial cells can lead to cancer bc of no contact inhibition and makes cancer cells migration and proliferation easier
Adhesion junctions
multi portein complexes that connect cells together at cell-to-cell and cell-to-matric junctions
Tight Junctions
- form seals that prevent molecules from passing in between epithelial cells
-separate the cell mem into basal and apical domains - not good at holding cells together
junctional complex
adhesion junctions, tight juntions and desmosomes to form a junctional complex
Gap junctions
Channels bt two cells
-exchange diff molecules
-made by joining two connexons
–> connexons made by 6 su
plasmodesmata
adhesion bt plant cells is mediated by cell wall components (instead of mem proteins)
plas mem of adjacent cells are continuous
imp in plant cell signaling
