Cell Interactions 1: The ECM Flashcards by M B

what do multicell organisms make contact with? (2)

other cells or ECM

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basal lamina

fibroblast & epithelial cells together make the basal lamina or basement membrane

compressed ECM, resilient to epithelial cells

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what tissue is almost entirely composed fo ECM material?

connective tissue

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what function does the ECM serve when it is a thin layer?

holds cells close together

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what function does the ECM serve when it is a thick layer?

cushions or protects

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how many specialized cell types do vertebrates have?

100+

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what type of ECM do plants, fungi & bacteria have?

a tough ECM, called ‘walls’

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what is the role of the ECM in anthropods? & what is the main component?

chitin is the main component

forms exoskeleton

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what are the most abundant polymers on earth?

chitin

cellulose

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what is the ECM composed of ?

primarily water

PROs

carbs

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what are the main macromolecules in the ECMs of animals?

Glycosaminoglycan (GAGs): polysaccharide with an amino grp

PROs –> collagen, elastin, fibronectin & laminin

Proteoglycans: PROs with GAGs covalently bonded

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where does the ECM come from?

cells secrete it & secrete surplus for other cells

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what type of ECM do fibroblasts have?

connective tissue ECM

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what type of ECM do osteoblast cells have?

bone-forming ECM (calcified ECM)

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what type of ECM do chondroblast cells have?

cartilage forming ECM

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when is the ECM calcified?

bones & teeth

cell wall of bacteria

shells of molluscs

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ECM function

Mechanical support

Biochemical barrier
Water soluble materials pass, lipid soluble materials cannot pass & macromolecules move slowly

A medium for:
Extracellular communication with CAMs
Positioning of cells in tissues through adhesions
Repositioning of cells in migration during cell development or wound repair (cells push along ECM)

Tensile strength for tendons

Compressive strength for cartilage

Hydraulic protection

Elasticity in the walls of blood vessels

Calcified for: bones/teeth, cell wall of bacteria & shells of molluscs

Chitinized to form the exoskeleton

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why are glycocalyx interactions not considered glycoPROs?

not covalently linked

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glycocalyx

carbs attached to the PM PROs & lipids

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what is the function of the glycocalyx?

Cell-cell interactions (carbs)

Cell substrate interactions (receptors) 

Mechanical protection 

Binding regulatory factors

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where is the basal lamina found?

epithelial layers & connective tissues

around muscle & fat cells
under epithelial tissues
Under endothelial lining of blood vessels

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functions of the basal lamina (basement membrane)

mechanical support for attached cells (prevents bursting)

generating signals

separating adjacent tissues

acting as a barrier to some macromolecules

establishes polarity (organelles orientate properly)

glycosaminoglycans

unbranched polymers of repeated modified disaccharides

Amino &amp; sulfate grps are added --> negative charge

what is the role of the amino or sulfate grps on glycosaminoglycans?

Attract ions (Na+) which attracts water causing the molecule to puff up into a gel

Account of 10% of the ECM, but puffing up enables them to take up 90% of the ECM volume which provides the compressive strength

what effect does the proteoglycan bound to GAG have?

increasing volume & water drawing capacity

Proteoglycan

PRO backbone covered with an extensive network of carbs GAGs attach to the backbone Sulfate grp still draws water in, creating a gel & provides cushioning

what molecules attract water to provide cushioning?

GAGs & proteoglycans

what part of the GAG & proteoglycan structure is sulfated?

carb

where are proteoglycans the most abundant?

in cartilage

Describe the ECM of bone

rich in collagen & proteoglycans bu hardened with calcium phosphate

collagen represents what percent of PRO in humans

25%

what is the most abundant material of the ECM?

collagen

what cell produces collagen?

fibroblasts

how many diff types of collagen are there?

collagen

fibrous PRO constituent of skin, cartilage, bone & other connective tissue

function of collagen

Scaffolding PRO, cells have receptors that attach to it Controls cell shape & differentiation Remodeled to help broken bones regenerate, wounds heal & directs blood vessels to grow in healing areas Fibrils shorten & lengthen to create tracks that cells can move on to go where they need to

what does hydroxylating proline & lysine do?

enables electrostatic interactions

structure of collagen

Trimer PRO, made of 3 alpha chains that intertwine to form a triple helix Proline & lysine get hydroxylated Fibrils come together for increased strength Crosslinked at hydroxylated residues

what is required for hydroxylating proline & lysine in collagen?

vit C

scurvy

occurs when diet is deficient in vit C vit C is required for hydroxylating for collagen fibrils to crosslink. Capillaries aren’t held in place & bleed out resulting in bruising

what are the probs that arise from collagen?

Scurvy – occurs when diet is deficient in vit C vit C is required for hydroxylating for collagen fibrils to crosslink. Capillaries aren’t held in place & bleed out resulting in bruising Increase cross-linking = decreased elasticity occurs with age --> wrinkles Mutation in type I collagen results in osteogenesis imperfecta – too much crosslinking results in thin, fragile bones which are brittle & break easily Mutations in other collagen genes results in hyper-flexible joints & extensible skin b/w there isn’t enough hydroxylation

how does collagen differ in tissues?

type of collagen & the arrangement of collagen

how is collagen arranged in tendons?

parallel, in line with the direction of the tensions exerted

how is collagen arranged in the eye's cornea?

perpendicular to other layers, gives strength while allowing light to pass

fibronectin

multifunctional PRO in ECM Link cells to ECM

fibronectin structure

Dimer - 2 arms with diff domains that can bind to components of the ECM & receptors

what is fibronectin's role in embryogenesis?

guides movement of cells works with collagen neural crest cells move out to form the nervous sys - follow tracks of fibronectin that other cells have laid out as a guide primordial germ cells migrate to site of gonads

what does integrin require to bind to the actin network?

adaptor PROs

integrin

integral membrane PRO

integrin structure

heterodimer, 2 polypeptides (alpha & beta chains) Cytosolic domains: bind to adaptor PROs that link integrins to elements of the cytoskeleton (ex: actin network) Extracellular domains: bind ligands in the ECM (ex: fibronectin, collagen etc.)

when do we see anchorage dependence of a cell lost?

cancerous cells

what is the function of integrins?

When integrins bind to ECM ligands, the structure of the cytoplasmic domain changes causing a signal cascade indicating to the cell to anchor Anchorage dependence is required for survival in vertebrates, lost in cancer cells Cells use this signal to regulate normal activities (cancer cells divide without this signal)

focal adhesion

how a cell attaches to ECM PROs Region of PM where there is a focal adhesion is rich in integrins Integrins anchor to actin microfilaments (with adaptor PROs) When adaptor PROs bind to integrin FAK is activated FAK signals to the cell to change shape, move or change in cell cycle