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Flashcards in Tissues-ECM/ECF Deck (19):

What is the ECM? and what are its functions?

A complex network of proteins and carbohydrates-made of fibrillar an non fribrillar components
Physical support, determine mechanical and pysiochemical proeprties of tissue, influenc growth, adhesion and differentiation


What organism have ECM?

All mutliple cell organism-even if simple


What is a quick description of connective tissue ECM?

Tissue rich in ECM, usually dissorganised. Specific sprecturm-Type I, II, III and IV collagen, MAG-fibronectin and fibrinogen, laminins, proteogrlycans (aggrcan, versican, decorin perlecan)


What is the molecular constitution of collagen? Which amino acids are in the helix?

28 types exist, with 42 genes-and each collagen is made of 3 alpha chains in a triple helix (not always same chains)
eg: colI has 2a1 and 1a2, while col II and col III have 3a2 and 3a3
specific gly-x-y, with x often proline and y
hydroxiproline-glycine allows the movement
- and each chain is about 1000aa and left handed


What is the basis of OI?

Gly->cystein mutation, leading to a kink (cant turn) and possibility to create extra S bonds -> abnormal agregation


How does collagen assemble? and how do you describe its biosynthesis?

each alpha chain bundles in triple helix with other alpha. These bundle onto into collagen fibril, which also condense in fibers (10-300nm)
It is synthesised as procollagen (with N and C terminal), and then become a triple helix. Then exocytosed, termini cleaved (make collagen), then get crossed linked with hydroxyproline and hydroxylysine to make fibrils. Cross links are covalent


What are cross links for collagen? what do they do?

Collagen fibrils get crossed linked with hydroxyproline and hydroxylysine to make fibrils. Cross links are covalent links that provide tensile strength ans stability-and the extend can change with age and tissue -> resist pull in one direction


What is type IV collagen? how does it assemble

Type IV is a non fibrillar collagen-and in instead fibril associated -called a network forming collagen
forms a sheet like network-essential for Basement membrane. They can form monomers, dimers, tetramers or supramolecukar agregates


What are elastic fibers? What is an exemple? describe it

Where collagen are important in tensile strnegth, elastic do elasticity. can be elastin (core of fiber) and microfibrils of fibrillin Its a proetein with a helical region that can cross link due to lysine bonding-it can stretch a lot and privides elasticity to tissue


What is Marfan's syndrome?

A mutation in fibrilin 1, leading to skeletal, occular and CVD issues-big part is longer limbs


What is laminin? where is it found and what is its main function?

3 chains, alpha, beta and gamme, making a large cross shaped molecule. its multi adhesive (can bind multiple other-including itself). Can bind surface receptrors, itself and other components of basement membrane.
3 headed triple coil of chain, with B and G chains for self assembly, and a chain for integrin, dystoglycan and perlecan binding


What disease is caused by laminin mutation?

Absence of a2 laminin 2 lead to congenital muscular dystrophy-hypotonia (low muscle tension), generalised weakness and deformes joints


What are Fironectins?

Glycoproteins of ECM-and all from one gene (alternative splicing). Also multi adhesive, and forms a large multi domain dimer, capable of interacting with receptor and ECM
Important role in cell adhesion, healing
No mutations in live humans-essential for life
Forms a V molecule linked by S-S bonds-bind collagen, integrin and heparin. RGD motif helps binding integrin
It binds integring (which binds itracellular actin) and provides continnuum of cytoskeleton between cells


What are proteoglycans? What families are there?

Core proteins with one or more glycosaminoglycan chains (GAG) covalently attached. They are long unbranched sugar of repaeting dissacharides-helps GAG to occupy huge volume and make hydrated gels-resistant to compression
several families baes on structural and functional-BM (perlecan), Aggregating (agreegan and hyaluronan), small leucine rich (decorin) and self surface (syndecans


What are some GAG chains? can they be categorised in groups?

GAG are repeating dissacharides with 1 aa. Most are sulfated or carboxylated, and HIGHLY negative. 4 main groups depend on sugar: Hyaluronan, Chondroitin sulfate, heparan sulfate and ketatan sulfate


What are characteristics of Hyaluronan?

Unique as its only a carbohydrate chain (no core protein)-synthesised at cell surface. Not sulfates, and can be up to 25000 dissacharides -absolutely massive


What are characteristics of Decorin?

Small proteoglycan, binding collagen fibers (1GAG), but essential for fiber formation and tensile strngth


What are charactertistic of aggrecan?

Major consituent of cartilage, lits a large proteiglycan with hundreds of GAGs (chrondroitin and keratan). usually bind htyluronan, and forms aggregates.
The GAGS are hydly sulfates, and its negaitive charges attract cations, and has large amount of water-under compression, gives up water->resist compressive force


What are consequences of aggrecan absence?

Aggrcan is a major component of Hyaline cartilages-as you get older, aggrgan is not made as fully and can be cleaved early, leading to osteoarthiritis-painful joins