Lecture 15 - Extracellular Matrix Flashcards
what type of tissues have little ECM
epithelial, muslce and nervous
what provides the strength in epithelial, muscl and nerous tissue
intermediate filaments
cell-cell junction
what does the protein composition of the ECM determine
the physical/mechanical proprties o the tissue
e.g. can be soft and transparent (eye)
or hard and dense (bone)
what important fibrous protein is a key compoent in ocnnective tissue
collagen
lots of types but collagen I makes up most
what does an increase in collagen mean
collagen I content correlates with tissue stiffness
e.g. low in brain but high in bone
what do SUN and KASH proteins do
link filamens in cytoplasm to nuclear lamins in the nucleus
can cause changes in gene expression (tumors more ikely to form in stiffer tissue)
what makes collagen in bone
osteoblast cells
deposits oriented fibres of collagen which are joined by calcium deposits
what re the 2 main components of the basal lamina
laminin
collagen IV
what cells make collagen in sikn/tendon
fibroblasts
where does trimerisation of pro-collagen (precursor to collagen) occur and what does it require
in ER
needs vit C - scurvy
procollagen = vry large, so how might it get transported
via cisternal maturation in golgi
too big for typical vesicles
where does procollagen assemble into fibrils
outside the cell
can c=onyl occur AFTER been cleaved by protease
how do collagen cfibres get properly aligned
cells will deposit them in an oriented way
and then cells eg fibroblasts will rearrange them by pulling on them
bit of a recap, what do protrusions in migrating cells adhere to the surface of the basal lamina with
the focal contacts which contain integrins
and the contractile actin bundles attach to focal contacts
what are integrins
TM proteins that link ECM to cytoskeleton
what linker proteins are used to bind cells to collagen
focal adhesions = fibronectin
basal lamina = laminin
what does fibronectin use to attach to the ECM
integrin
remember it is a protein that links stuff from outside of cell to inside
how do integrins get inactivated and when
via phosphorylation
during mitosis (at other times too, but important in mitosis)
what parts of cytoskeleton can integrin interact with
actin and intermediate filaments
what fills the spaces between collagen in ECM
glycosaminoglycans (GAGs)
vry big cuz vry hydrophillic and will bind a lot of water
what can GAGs be covalently linked to
secreted proteins
to form proteoglycans
how do GAGs generate swelling pressure
bind water molecules (lots of -ve charges which make it hydrophillic)
how does cartilage resist compression
swelling pressure generated by GAGs
pressure gets resisted by collagen fibres = outward force
idek tbh
what is hyaluronan
polysaccharide synthesised by hyaluronan synthase
also allows resistant to pressure
why do plants rely on cell wall for strength
cuz no intermediate filametns
what type of cell wall allows growth of plant
primary cell wall
cellulose structure
polysaccharide
~16 strands held together by H bonds in a microfibril
what is the polysaccharide that acts as a gel in plant cell wall (and some functions)
pectin - fills spaces, resists compression, sticks neighbouring cells together
what does the orientation of cellulose determine
the axis of cell growth
where is cellulose synthesised
at the cell membrane (same as hyaluronan)
what will make the cellulose and assemble them in to microfibrils
cellulose synthase complex
how are MT involved in cellulose syntehsis
MT inside the cell determine the orientation of the cellulose fibres outside the cell
