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extracellular matrix
thatcher self study
| Question | Answer |
|---|---|
| what is the function of the extracellular matrix? | it provides shape and resiliency to the tissues and organs. it also provides a medium for cells to interact with their extracellular environment |
| what are the major components of the ECM? | collagen, elastin, hyaluronan, and proteoglycans. each is found in most tissues but they are major constituents of connective tissues such as cartilage, tendons, bone, and basal lamina. |
| this is the most abundant protein in the body, making up half of our protein by weight | collagen |
| how many distinct types of collagen are there? | fourteen |
| what is the function of collagen? | it provides tensile strength by resisting stretching forces |
| what are the structural units of collagen | primary subunits are left anded helical polypeptides. these associate into right handed triple helices, which are bundled together to form collagen fibers |
| collagen subunits contain residues of which amino acids? | prolines and glycine |
| scurvy results from a dietary deficiency of this | vitamin C |
| how is collagen crosslinked? | tropocollagen triple helices are bundled together into fibers by covalent cross links between lysine residues near their termini. enzyme driving this rxn is lysyl oxidase. |
| collagen is produced by these cells throughout the body | fibroblasts |
| collagen is made by these cells in cartilage | chondroblasts |
| collagen is made by these cells in bone | osteoblasts |
| when collagen is first translated it is known as this | procollagen |
| this is a clinical defect in which excess collagen is formed | fibrosis (ex: pulmonary fibrosis, athersclerosis, and scar tissue in liver due to over consumption of alcohol) |
| this is a clinical defect in which there is a lack of hydroxyproline residues due to dietary deficiency of vitamin C. symptoms include weak and malformed bones, teeth, skin, blood vessel walls, and dermal hemorrhaging | scurvy |
| this is a clinical defect in which mutations resulting in underproduction or incomplete procesing of different collagens occur. symptoms range from loose skin and joints, to neonatal death. contortionists often have this disorder | Ehlers-Danlos syndrome |
| this is a clinical defect in which there are mutations of type I collagen, which interfere with triple helix assembly. the more severe mutations result in lethality in utero or soon after birth. less severe mutations produce brittle bones | osteogenesis imperfecta |
| this is the principle component of elastic fibers | elastin |
| what is the function of elastin? | provides tissue with the ability to return to its original size and shape. |
| what is the tissue distribution of elastin? | elastin is abundant in pliable tissues such as the ligaments and arterial walls. there is little elastin in tendons, skin, and loose CT |
| which structure in the body has the greatest abundance of elastin? | aortic arch |
| marfan's syndrome results from a mutation in this gene | fibrillin |
| where is elastin formed? | tropoelastin polypeptides are synthesized in the RER and secreted into the extracellular space. there they congregate around fibrillin |
| what enzyme crosslinks elastin subunits? | lysyl oxidase (same as collagen) |
| A tropoelastin unit consists of what? | alternating hydrophobic and hydrophilic domains |
| describe antitrypsin deficiency | antitrypsin is an inhibitor of various proteases such as elastase. homozygous mutatnts are predisposed to emphysema because the elastin in their alveolar walls are degraded. |
| polysaccharides composed of disaccharide repeats that are modified with groups such as nitrides, sulfides, and carboxyls | glycosaminoglycans |
| an extremely large glycosaminoglycan, consisting of up to fifty thousand glucoronic acid/ acetylglucosamine repeats. these are the only glycosaminoglycans that commonly exist free in the extracellular matrix. | hyaluronans |
| glycosaminoglycans bound to a core protein. they are often crosslinked with other components of the extracellular matrix such as collagen, as well as the plasma membrane. they help to anchor cells to the basal lamina. | proteoglycans |
| consist of as many as 100 proteoglycans linked to a hyaluronan core. they form massive complexes, up to 200 million daltons. they are particularly prevalent in cartilage, where they function to resist compression | aggrecans |
| extracellular matrix crosslinking proteins to promote crosslinking of multiple factors found in the extracellular matrix. they possess multiple binding domains | multiadhesive matrix proteins |
| these crosslink the fibers in the basal lamina. it is a glycoprotein consisting of three polypeptides with binding sites for multiple factors such as heparin, sulfated lipids, and type four collagen. | laminin |
| these crosslink extracellular matrix fibers outside of a basal lamina. they consist of two polypeptides linked by disulfide bonds, with binding domains for collagen, heparin, integrin and fibrin | fibronectins |
Created by:
aferdo01
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