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What is the ECM?
- the environment in which cells exist in a living organism
- --> proteins and molecules expelled into ECM
- --> tells it whether it is in the right matrix or whether things are okay or disrupted
How the connective tissue underlying an epithelium arranged?
it contain a variety of cells and ECM components. The predominant cell type is the fibroblast, which secretes abundant extracellular matrix
The ECM contains __ and __.
proteins and large polysaccharides called GAGs (glycosaminoglycans)
structure: unbranched polysaccharide chains of repeating disaccharide units: 70-200 sugar units long; have lots of negative charges
GAGs function (1-3)?
1) take up space due to structure and unbranched nature= can fold up tightly; extended conformation
2) attract cations (ex: Na+), which in turn attracts water--> swell up, creating turgor pressure (resistance to compression)
3) Help regulate secreted proteins; activation and deactivation of certain proteins; spaces and channels produced by GAGs can be affected
most abundant and largest protein with no particular conformation; extended and taking up space; creates channels
Why is hyaluronan unique?
- unique in that its non-sulfated nor covalently attached to proteins
- abundant in joints= resist compression
- acts as a space filler in wound healing process to help repair wound
- not linked to proteins
What is proteoglycan?
polypeptide backbone known as core protein attached to serine residue and disaccharide repeats to produce it
perform same function
Explain the linkage between a GAG chain and its core protein in a proteoglycan molecule.
A specific link tetrasaccharide is first assembled on a serine side chain. In most cases, it is unclear how the particular serine is selected, but it seems that a specific local conformation of the polypeptide chain, rather than a specific linear sequence of amino acids, is recognized. The rest of the GAG chain, consisting mainly of a repeating disaccharide unit, is then synthesized, with one sugar being added at a time
What are the two types of protein?
structural and adhesive
Explain the ECM of a fibroblast.
Everything is really collagen except a large cell
fibrils are organized into bundles that run approximately at right angles to one another. Some are longitudinal and others are in cross section.
25% mass; most abundant in our bodies
coded for by 25-30 different collagen genes in the genome; basic sequence is pro-pro-gly, but can vary in different families (ex: acidic vs. basic)
What is always paired in collagen?
Always have an acidic collagen paired with a basic collagen
Tisue changes, developmental changes, always pair acidic with basic
What can happen to the lysines and prolines?
Explain hydroxyproline more.
they can be hydroxylated
- hydroxylysine is infrequent
- hydroxyproline usually occurs post translation
- protein molecules form; ends need to be cut off before polymerization
- Hydroxyproline is very rigid; not much stretch (resistant)
What can form between the side chains within collagen?
Cross-links form between modified lysine side chains within a collagen fibril.
- Covalent intramolecular and intermolecular cross-links are formed in several steps.
- 1) First, the extracellular enzyme lysyl oxidase deaminates certain lysines and hydroxylysines, to yield highly reactive aldehyde groups
- 2) Thealdehydes then react spontaneously to form covalent bonds with each other or with other lysines or hydroxylysines.
- Most of the cross-links form between the short nonhelical segments at each end of the collagen molecules
Blood vessels describe?
tissues constantly change shape and size; strip all but ECM--> elastic fibers
structural but has no structure to it
has cross-links: can stretch out but get compact again
it has different crosslinks than colalgen
Explain stretching of a network of elastin molecules.
the molecules are joined together by covalent bonds to generate a cross-linked network.
multiple binding domains: attach to ECM and hold it together
Fibronectin is made of two large subunits connected by S-S bonds by cysteine residues--> coded for by one gene (50K bases long and contains about 50 exons)--> alternative splicing creates different types; different binding domains
- abundant in fetal stage
- --> circulates in blood and binds to molecules in blood
- --> seen in wound healing; helps clotting and wound healing
- Assist with cell migration and proliferation
highly insoluble deposited at surface of cells; makes filaments in combo with surface of cell and ECM proteins
The __ is produced by __. It can allow/ prevent activation from happening. It is a __ that does wht?
- basal lamina
- allows some molecules in and go from one cell type tissue to another
Explain the structure of laminin
The multidomain glycoprotein is composed of three polypeptides (alpha, beta, and gamma) that are disulfide-bonded into an asymmetric crosslike structure. Each of the polypeptide chains is more than 1500 amino acids long.
Several functional domains binding to ECM components
Sheets laid down by fibroblasts and tissue its located in
can be a highway for cell migration
What does laminin do?
induces cell differentiation
contact may be a trigger for differentiation or prevention
What does the ECM do?
Interactions within the ECM inform the cell that they are in the right environment