CBG Lecture 38: Extracellular Matrix

Question 1

define ECM - extracellular matrix

Answer 1

complex network of polysacchs and proteins secreted by cells for strengthening tissues

Question 2

what is a cell junction

Answer 2

directly links cells together in flexible tissues

Question 3

what are the two types of animal tissue

Answer 3

connective

epithelial

Question 4

what are the two main types of extracellular molecules that make up the matrix

Answer 4

GAGs - gycosaminoglycans

Fibrous proteins - collagen,lamins,elastin,fibronectin

Question 5

what are GAGs

Answer 5

glycosaminoglycans
extracellular molecules that make up the matrix - usually found covalently linked to protein in the form of proteogylcans

Question 6

what are proteoglans

Answer 6

GAGs - glycosaminoglycan polysaccharide chains usually found covalently linked to protein

Question 7

name some fibrous proteins

Answer 7

collagen
laminin
elastin
fibronectin

Question 8

what are epithelial sheets

Answer 8

sheet of cells covering surface of tissue which creates a barrier for multicellular orgs

Question 9

what are the four main structures of cell

Answer 9

1. epithelial tissue
2. basal lamina
3. connective tissue
4. collagen fibres

Question 10

what are the different epithelial tissues

Answer 10

simple
stratified
columnar
cuboidal
squamous

Question 11

how are epithelial sheets polarised

Answer 11

have two faces: apical (exposed) and basal (rests on connective tissue)

Question 12

what is basal end of epithelial sheet supported by

Answer 12

basal lamina - thin sheet of ECM

Question 13

what is basal lamina composed of

Answer 13

type 4 collagen and laminin

Question 14

what is laminin

Answer 14

links integrin - in the plasma membrane of epithelial cells - to CT (like fibronectin)

Question 15

what links integrin to connective tissue

Answer 15

laminin

Question 16

what is a cell-cell junction

Answer 16

connection between 2 cells or between cell and ECM

separates apical/basal surface and helps in cell-cell communication

Question 17

give the names of cell-cell junctions

Answer 17

tight junction
adherens junction
desmosome
gap junction
hemidesmosome

Question 18

what is the function of a tight junction

Answer 18

seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them

Question 19

what is an adherens junction

Answer 19

joins an actin bundle in one cell to a similar bundle in a neightbouring cells

Question 20

what junction seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them

Answer 20

tight junction

Question 21

what junction connects actin bundle in one cell to a similar bundle in neighbouring cells

Answer 21

adherens junction

Question 22

what is a desmosome

Answer 22

joins the intermediate filaments in one cell to those in a neighbour

Question 23

what joins the intermediate filaments in one cell to the intermediate filaments of a neighbour

Answer 23

desmosome

Question 24

what is a gap junction

Answer 24

forms channels that allow small water soluble molecules including ions to pass from cell to cells

Question 25

what junction provides channels that allows small water soluble molecules including ions to pass from one cell to another

Answer 25

gap junction

Question 26

what is a hemidesmosome

Answer 26

anchors intermediate filaments in a cell to the basal lamina

Question 27

what anchors intermediate filaments in a cell to the basal lamina

Answer 27

hemidesomosome

Question 28

what are CAMs

Answer 28

cell adhesion molecules

Question 29

how to cells adhere to other cells

Answer 29

via transmembrane cadherin molecules that are connected to the cytoskeleton via linker proteins

Question 30

what are the major families of cell adhesion molecules

Answer 30

1. cadherins 2. Ig-superfamily 3. integrins 4. selectins

Question 31

name some cadherins

Answer 31

E-cadherins - has calcium binding sites

Question 32

what do integrins contain

Answer 32

fibronectin

Question 33

what do selectins contain

Answer 33

sugars lectins glycoproteins

Question 34

what do spatial and temporal expression of CAMs regulate

Answer 34

adhesion

Question 35

what are the roles of CAMs

Answer 35

proliferation migration differentiation fighting infection - movement of WBCs

Question 36

why is it so important to have CAMs

Answer 36

disruptions in cell-cell interactions have devastating effects on embryo development cancer metastasis

Question 37

what are the models for generating cell-cell adhesion

Answer 37

homotypic (cis) homophilic heterophilic (trans)

Question 38

outline cell-cell adhesion via homophilic binding

Answer 38

molecules on one cell bind to other molecules of the same kind on adj molecules

Question 39

outline cell-cell adhesion via heterophilic binding

Answer 39

molecules on one cell bind to molecules of a different kind on adj cells

Question 40

outline cell cell adhesion by binding through an extracellular linker

Answer 40

cell surface receptors on adj cells are linked to one another by secreted multivalent linker molecules

Question 41

how do cadherins link cells

Answer 41

via the homophilic mechanism - calcium dependent | the longer CAM = stronger the chain

Question 42

what conformations do integrins exist in

Answer 42

low affinity - inactive | high affinity - active

Question 43

what do integrins do

Answer 43

mediate cell-adhesion to the ECM by bridging between ECM and cytoskeleton

Question 44

what is the level of adhesion of a cell affected by

Answer 44

the expression level on integrin cell surface

Question 45

what is the basal lamina

Answer 45

thin mesh of ECM molecules - important in tissue repair and development

Question 46

what does the basal lamina contain

Answer 46

multiadhesive matrix proteins laminin (interact with integrins @ hemidesmosomes) type 4 collagen perlecan - proteoglycan - bind diverse partners, crosslink components

Question 47

what are main components of basal lamina

Answer 47

type 4 collagen laminin entactin perlecan

Question 48

name some connective tissue

Answer 48

tendon -tough and flexible bone -hard and dense cartilage - shockabsorbing soft - jelly in eye

Question 49

what do various types of CT depend on

Answer 49

collagen

Question 50

what are collagen fibrils organised into

Answer 50

bundles

Question 51

discuss structure/flowchart of a collagen fibril

Answer 51

single collagen peptide chain -> triple stranded collagen molecule -> collagen fibril -> triple stranded structure

Question 52

what is collagen rich in

Answer 52

proline and glycine

Question 53

what is CT release by skin called

Answer 53

fibroblasts

Question 54

what is CT released by bone called

Answer 54

osteoblasts

Question 55

how is collagen released by fibroblast

Answer 55

exocytosis

Question 56

what does fibronectin and integrin do

Answer 56

helps attach CSK to ECM

Question 57

what are preoteoglycans - what do they do

Answer 57

help resist compression and function as space fillers in ECM

Question 58

what are GAGs made of

Answer 58

Extra cellular proteins linked to negatively charged polysacchs - glycosaminoglycans -GAGs