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a. Proteoglycans
i. __ complex
ii. consists of a core protein to which chains of __are covalently attached
1. each is composed of a repeating disaccharide: __, where A and B represent two different sugars
2. __are higly acidic due to the presence of both __ and __ groups attached to the sugar rings
- protein-polysaccharide
- glycosaminoglycans
- A-B-A-B-A-
- GAGs
- sulfate and carboxyl
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i. proteoglycans of the ECM may be assembled into gigantic complexes by __ of their __ to a molecule of __, a nonsulfated GAG
ii. Because of the negative charges borne on the __, __bind huge numbers of __, which in turn bind large numbers of water molecules
- linkage
- core proteins
- hyaluronic acid
- sulfated GAGs
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1. as a result, proteoglycans form a __ that __ and __
a. this property complements that of the adhacent collagen molecules, which __ and __
porous, hydrated gel
fills the EC space and resists crushing forces
resist pulling forces and provide a scaffold for the proteoglycans
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i. Together, __ and __ give __and other EC matrices strength and resistance to deformation
ii. the EC matrix of bone is also composed of __ and __, but it becomes hardened by impregnation with __
1. both __ and __ are taken widely as health supplements with the aim of improving the condition of skin and joints
- collagen and proteoglycans
- cartilage
- collagen and proteoglycans
- calcium phosphate salts
- sulfated and nonsulfated GAGs
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a. Fibronectin
i. __= a structure made up of a network of interacting components
ii. consists of a linear array of distinct “__” that gives each polypeptide a __construction
iii. each is constructed from a sequence of approx __
1. __ found as part of many other proteins
- matrix
- building blocks
- modular
- 30 independently folding Fn modules
- Fn-type modules
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i. presence of shared segments among diverse proteins suggests __
ii. in __, the 30 or so structural modules combine to form __
- evolution
- fibronectin
- five or six larger functional domains
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i. each of the two polypeptide chains that make up a firbonectin molecule contains:
- 1. binding sites for numerous components of the ECM which facilitate interactions that link these diverse molecules into a stable, interconnected network
- 2. binding sites for receptors on the cell surface, which hold the ECM in a stable attachment ot the cell
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a. binding activities of fibronectin molecules are enhanced by __ that pull on these fibrous proteins and unfold its component molecules, which __ the __
- mechanical forces
- exposes the binding sites
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i. importance evident during __, which Is characterized by waves of cell __during which different cells follow different routes from one part of the embryo to another
1. migrating cells are guided by proteins
a. ex: neural cell migration
- embryonic development
- migration
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a. Laminin
i. family of __ that consist of __ linked by __ and organized into a molecule resembling a cross with three short aarms and one long arm
ii. at least __identified
iii. __ influence cell’s potential for migration, growth, and differentiation
- extracellular glycoproteins
- three different polypeptide chains
- disulfide bonds
- 15
- extracellular laminins
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i. in addition to binding tightly to cell-surface receptors, they bind to other __, to __, and to other components of __
ii. __ and __ molecules of absement membranes form separate, but interconnected, networks
1. these interwoven networks give basement membranes both __ and __
- laminin moeclues
- proteoglycans
- basement membranes
- laminin
- type IV collagen
strength and flexibility
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a. Dynamic properties of the ECM
i. can do what as they are pulled on by cells and contract when tension is relieved
ii. components are subject to continual __ and __, which renew the matrix and allow remodeling
- stretch several times their normal length
- degradation and reconstruction
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i. __carried out __ that are either secreted into the EC space or anchored to the plasma membrane
1. as a group, these can do what although as individual family members cannot
2. thought to be involved in tissue remodeling, etc.
3. excessive activity- disease like arthritis, tooth and gum disease, etc.
- degradation
- matrix metalloproteinases
- digest nearly all of the ECM components
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