2-ECM Flashcards
what is the function of the ECM?
-structural
-signaling
-mechanical support
-scaffold
-regulation
what is one of the most defining features of the animal body
ECM
how does ECM function in structural support
-contains BM and interstitial matrix
-differs in strength and texture due to molecules in ECM and how they are arranged
how does ECM work in scaffolding?
-provides tissues with shape and provides scaffold to regenerate tissue
how does ecm work in cell signaling
-allows cell to know where it is and what it is
-transmits mechanical signals to cells that can alter their behavior
how does ecm work in regulation of growth factors?
-growth factors that are released from cells bind the ecm and are stored there until they are released in response to mechanical stress
what can activate/destroy growth factors in ecm
proteases
what relationship do cells and ecm have?
bidirectional
how do cells and ECM have a bidirectional relationship?
-ECM is synthesized and organized by the cells within it
-ECM then signals back to the cell
what cells make ECM
-fibroblasts, chondroblasts, osteoblasts, any cell can make ECM
what is the basement membrane?
specialized form of ECM that underlie virtually all epithelia
3 main classes of molecules in ECM
1.fibrous proteins
2. glycoaminoglycan polysaccharide chains
3. multidomain glycoproteins
2 types of fibrous proteins
collagen and elastin
what is the function of collagen
confer tensile strength
collagen _____ and ____ affects tissue structure
composition and arrangement
structure of collagens:
-triple helix composed of 3 alpha chains that wind around each other in rope-like structure
-rich in glycine and proline
small size of glycine allows for ______
tight packing of helices
ring structure of proline ______
stabilizes the helix
to assemble into functional collagen molecules , the alpha chains undergo _______
post-translational modifications
how are collagens assembled
into fibrils and then fibers
prolines and lysines undergo what?
hydroxylation
what does hydroxylation of prolines and lysines allow for?
intra and inter molecular cross linkage
individual alpha chains self assemble in ER which forms
procollagen
fibrils are strengthened by:
formation of cross links between lysine residues
what are 2 major types of collagen ?
fibrillar
network forming
what is fibrillar collagen
long, rope-like fibrils
type 1, 2, 3, 5, 11 collagen
-bone, skin, tendons, cartilage
what is network forming collagen?
-forms basement membranes
-anchors basement membrane to underlying tissue
-type 4 collagen
how does collagen play a role in wound healing
-fibrillar collagens form a major portion of the connective tissue at repair sites
________ collagen synthesis interferes with wound healing
impaired
what is fibrosis
excessive collagen deposition
what is the function of elastic fibers
allow tissues to stretch and recoil
what are elastic fibers composed of
-elastin molecules covered with a sheath of glycoprotein microfibrils
-elastin has alternating hydrophobic and alpha helical segments
-hydrophobic regions confer elastic properties
-helical segments cross link
glycosaminoglycan polysaccharide chains form what?
hydrated gels (ground substance)
what are GAGs
-unbranched polysaccharide chains that are negatively charged
what is the purpose of negatively charged on GAGs
hydrophilic, and allows them to stay in chains
GAGs occupy a huge ______ relative to ______
volume
molecular weight
____ is a major polysaccharide component of ECM
hylauronic acid
HA is the simplest of ______
glycosaminoglycans
HA function
joints
what are proteoglycans?
long, unbranched GAG chains covalently linked to a core protein
role of proteoglycans?
signaling roles
examples of multidomain glycoproteins
-fibronectin
-laminin
what are multidomain glycoproteins
glycoproteins with multiple domains that serve as binding sites for matrix proteins and for surface receptors
located in ECM
________ is the most abundant ECM adhesive protein
fibronectin
what does the ECM consist of
-fibrous proteins and multi-adhesive glycoproteins embedded in ground substance
what is ground substance formed by?
glycoaminoglycans
what is the main producer of the ECM constituents?
fibroblasts
collagen synthesis:
- alpha chains are synthesized in a long precursor form with propeptides at the N and C terminus
- propeptides prevent triple helixes from associating with each other
- lysine and proline residues are hydroxylated
- select hydroxyprolines are glycosylated
- 3 pro alpha chains self assemble to form a procollagen triple helix
- procollagen molecules secreted
- cleavage of N and C propeptides allows for self-assembly of triple helices into fibrils
- fibrils assemble into fibers
hydroxylation of lysine and proline residues allows for ____
formation of crosslinks between different alpha chains
what do crosslinks do?
strengthen the collagen fibrils and fibers
The enzyme required for proline hydroxylation requires ______ as a cofactor
vit. C
collagen type 1 found in :
bones/skin
collagen type 2 found in:
cartilage
structure of fibril associated collagens
triple stranded helices are interrupted by non helical domains that allow flexibility.
-pro-peptides are not cleaved
type 4 collagen is the major collagen of :
basement membranes
which type of collagen is the most flexible structure
network forming collagen
how does type 4 collagen interact
via uncleaved terminal domains to assemble into a flexible network
what does anchoring collagens do?
anchor basement membranes to CT
how is elastin arragned
fibers or discontiuous sheets
the elastin protein is composed of :
alternating segments of hydrophobic and alpha helical regions
elastic fibers are interwoven with _____
inelastic collagen fibrils
process of elastic fiber formation
elastogenesis
