cell biology 8 Flashcards
what is the extracellular matrix
complex network of macromolecules between cells
- cells make, organise and degrade it
what is the functions of the extracellular matrix
- connects cells
- provides support
- regulates cellular survival, development, migration, proliferation, shape and function
what are the major classes of macromolecules
- glycosaminoglycans - large, linear, charged proteoglycans
- fibrous proteins - collegen and elastin
- glycoproteins - asparagine- linked oligosaccharides
what are glycosaminoglycans (GAGs)
- contain unbranched polysaccharides
- have amino sugars and acidic disaccharide repeats
- long and linear
what is the example of a GAG and what is its function
- aggrecan
- have over 100 GAG chains
- major component of cartilage
- can aggregate along hyaluronan molecules
what is the structure of basal lamina
- thin layer of specialised extracellular matrix
- lies beneath all epithelial cells
what is the function of Basel lamina
- determine cell polarity
- influence cell metabolism
- organise the proteins in adjacent plasma membranes
- promote cell survival, proliferation and differentiation in tissue repair
- highway for cell migration
what is laminin
- heterotrimeric glycoprotein - alpha, beta and gamma chains
- primary organiser of the basal lamina
that does the basal lamina do in the kidneys glomerulus
- selective filter
- prevents macromolecule loss in urine
what happens to the kidney glomerulus when having diabetes
- selective permeability lost
- globular basement thickening
- messangial hyperthrophpy and ECM deposition
what are cell matrix adhesion complex made from and what are they used for
- 8 different beta chain genes and 18 different alpha chain genes
- binding to matrix ligands affected by Ca and Mg concentration
- linked to cell cytoskeleton
- some cells need to be attached to ECM to survive
where are actin linked cell matrix junctions found
Cellular: Actin filaments
Cellular adaptors: Vinculin, Talin, kindlin
Cell membrane: Integrin
Extracellular Matrix: ECM Proteins
where are hemidesmosomes found
- Common in epithelial cells
Cellular: Intermediate filaments
Cellular adaptors: Plectin, BP230
Cell membrane: Integrin, Collagen XVII
Extracellular Matrix: Lamin
what is cell intergrins functions
- Integrins are either active or inactive
- Need to switch between the two to move a cell
- Regulated by GPCR signalling
- Note talin unwinding as a mechanical sensor
what are matrix metalloproteinases
- enzymes that degrade ECM
- produced as zymogens - inactivated form
what is the function of Matrix metalloproteinases
allows:
- cell penetration
- cell migration
- angiogenesis
- tissue remodelling
what are the stages of cell migration
1) Actin polymerisation → protrusion
2) Engorgement of the protruding region
3) Retraction of actin at the neck
4) crosslinking of microtubules into a stable bundle
what occurs in neuromuscular synapse adhesion
- muscle is surrounded by basal lamina
- margin secreted from axon into muscle ECM
- binds LRP4/MuSK again receptors
what does Rho-GTpases in cell migration do
- active Rho-GTP induces growth cone to collapse
- requires myosin-dependent contractions of actin cytoskeleton
what are the features of collagen
- Fibrous protein
- Long, stiff, triplestranded helical structure
- Rich in proline and glycine: Gly-X-Y
- Most abundant proteins in mammals: 25% total protein
- 42 distinct human genes
- > 40 “types” of fibres
- Collagen fibrils resist tensile forces
what are the types of collagen
Type I - Fibrillar collagen (Skin and Bone)
Type IX and XII - Fibril-associated collagens
Types IV (Basal lamina) and VII (Anchoring fibrils) - Network-forming collagens
what are the stages of collagen synthesis
- ER ribosomes translate preprocollagen
- Selected Pro and Lys are hydroxylated to hydroxyproline and hydroxylysine
Note: Proline hydroxylation requires ascorbic acid (vitamin C) Scurvy…. - Some hydroxylysines are glycosylated
- Three Pro-α chains combine in a triple-stranded, helical procollagen
- Hydroxyl groups form interchain hydrogen bonds
- N- and C-terminal propeptides cleaved off
Procollagen → collagen - Collagen assembles in the extracellular space to form collagen fibrils
- Cross-links formed between modified lysine side chains…….
