Extracellular Matrix Flashcards
secondary plant cell wall
- found in stronger structures (like tree trunks)
- has three layers with different orientations
- located in between the plasma membrane and primary wall
cellulose
glucose monomers connected by B1-4 linkages
cellulose synthase
polymerizing enzyme that moves within the plane of the plasma membrane along tracks of intracellular microtubules as cellulose is formed
scurvy
caused by a lack of vitamin C (coenzyme ascorbic acid); vit. c is needed for the conversion of proline to hydroxyproline; without vit. c proline isn’t hydroxylated; collagen all over the body is affected
lignin
modified phenols; lignin units bind in random ways and fills the space of the cell walls
cellulose synthesis
- cellulose microfibrils synthesized on the exoplasmic face of the plasma membrane from UDP-glucose formed in the cytosol
- microtubules orient to guide S1, then rotate to guide S2, then S3 and guide the cellulose synthase
hyaluronan
- 25,000 disaccharides, no sulfates, no protein
- repeats of glucuronic acid and glucosamine
- synthesized at the cell surface
- hydrophilic, can interact with water –> helpful in synovial fluid and cartilage
largest “molecule” in the body
hyaluronin with proteoglycans; can include aggrecans of collagen
fibronectin
- multiple binding regions
- RGDS amino acid sequence binds to cell surface
- able to bind many components of ECM together; holds ECM together
- important role in cell migration/differentiation
- dimeric molecule
glucosamine
component of synovial fluid, cartilage; make a great lubricant because it attracts water
chondroitin sulfate
like hyaluronan but n < 250 and has sulfates
structure of collagen
single peptide of collagen is helical (alpha-helix); three collagen peptides come together to make a triple helix
glycosaminoglycans (GAGs)
variable group characterized by high carbohydrates
another name for basal lamina
basement membrane
integrins
- transmembrane surface receptor which binds fibronectin and/or laminin; binds cytoskeletal proteins on the cytosolic face
- binds amino acid sequence RGD on matrix proteins, such as fibronectin
diseases involving deficient collagen synthesis
- Ehler’s-Danlos
- Osteogenesis Imperfecta
- Scurvy
role of growth factors with ECM
- growth factors can be bound to ECM
- if the ECM gets damaged or disrupted, then the growth factors get released
- damage to ECM means damage to cell; release of growth factors allows repair response –> angiogenesis, epithelial cell proliferation etc.
- the ECM is a reservoir for growth factors
composition of bone
proteoglycan/collagen network and calcium hydroxyapatite
basal lamina
a sheet-like substrate for epithelial cells ; provides an important base to which epithelial and endothelial cells attach
result of too much collagen
too much collagen laid down at wound site leads to tissue not being very stretchable
collagen that predominates in the basal lamina
type IV collagen
primary plant cell wall
extremely thin; cellulose oriented randomly and expands in all directions
components of primary cell wall in plant cell (from PP photo)
- pectin
- cellulose
- microfibril
- hemicellulose
laminin
- characterized by 3 proteins in a cross-link structure
- important feature: many binding sites and domains
- binds to collagen, sulfated lipids, integrins, CHOs
- limited to the basal lamina
- binds to other features of the ECM; helps onnect the overall structure
two-component system of plant cell wall
- cellulose fibers
- lignin
heparan sulfate
- able to bind FGF (fibroblast growth factors)
- can bind chemokines on endothelial surface of vessels (WBC migration)
- able to bind and activate ATIII (antithrombin III) to inhibit clotting
Ehler’s-Danlos Syndrome
rubber man syndrome; globular ends aren’t correctly removed so collegen is poorly joined, causing weak joints; can lead to weaken blood vessels –> aneurysms
pectin
polymer of D-galacturonic acid and monosaccharides; modified sugars
proteoglycans
- GAG linked to protein
- 20 to 250 disaccharides; sulfates and proteins
- glycolylation in ER/golgi
- up to 95% CHO in proteoglycan
most abundant protein in the body
collagen
4 main classes of glycosaminoglycans (GAGs)
- Hyaluronan
- Chondroitin Sulfate
- Heparan Sulfate
- Keratan sulfate
plasmodesmata
- this is what plant cell walls have instead of gap junctions
- channels that connect the cytosol of a cell with that of an adjacent cell
- gap large to allow entry of viruses
synthesis of collagen
see page 2 ECM notes
specific examples of problems involving too much collagen
pulmonary fibrosis – difficulty with lung expansion
liver scar tissue – caused by excessive drinking; cyrosis of the liver leads to functional hepatocytes being replaced by collagen
linus pauling
found that collagen has a triple helix
Osteogenesis Imperfecta
brittle bone syndrome; glycine gets replaced with another amino acid which causes disruption in the helix –> results in little or no helix formation; so deformed that the body detects it as foreign and degrades it, causing brittle bones
pricipal structural components of basal lamina
collagen and laminin
