Topic 12

Question 1

extracellular matrix (ECM)

Answer 1

fills spaces between cells and bind cells and tissues together

Question 2

ECM composition

Answer 2

tough fibrous structural proteins embedded in ground substance

Question 3

ground substance

Answer 3

gel-like polysaccharide material

Question 4

specialized adhesion proteins

Answer 4

anchor cells to ECM

Question 5

collagen

Answer 5

major structural protein of ECM; most abundant protein in animal tissue

Question 6

The collagens are a large family of proteins containing at least ___ different members

Answer 6

27

Question 7

collagen form…

Answer 7

straight fibrils and fibres and networks

Question 8

4 basic categories of collagen

Answer 8

fibril forming, network forming fibril associated anchoring, and transmembrane

Question 9

Type I collagen class

Answer 9

fibril forming

Question 10

Type IV collagen class

Answer 10

network forming fibril associated

Question 11

Basic structure of collagen

Answer 11

repeats of Gly-X-Y (where X is usually proline and Y is usually a hydroxyproline) to form triple helices.

Question 12

hydroxyproline

Answer 12

stabilizes colagen triple helices

Question 13

collagen fibrils

Answer 13

collagen triple helices line up in a staggered arrangement, and are cross-linked together
-assemble within ECM

Question 14

procollagen

Answer 14

partially processed precursor of collagen from cell via ER/Golgi

Question 15

collagen is secreted as subunits of _______ that then assemble into ____ and ____ outside of the cell

Answer 15

pro collagen, fibrils, fibres

Question 16

type IV collagen

Answer 16

network forming collagen; numerous interruptions of helical regions making them more flexible and cross linked to networks

Question 17

elastic fibers

Answer 17

found in connective tissues and abundant in organs that regularly stretch and return to shape (lungs)

Question 18

elastin

Answer 18

principal protein of elastic fibres; cross-linked into a network by covalent bonds between side chains of lysine residues

Question 19

GAGs; glycosaminoglycans

Answer 19

gel-forming polysaccharides that consist repeating units of disaccharides

Question 20

proteoglycans

Answer 20

higher order structures of GAGs (covalently linked to proteins) un to 95% carbohydrate by weight

Question 21

chondroitin sulfate

Answer 21

GAG attached to a core protein

Question 22

larger proteoglycan aggregates

Answer 22

proteoglycans interact with hyaluronan chains to form “bottle brush structures”

Question 23

matrix adhesion proteins

Answer 23

responsible for linking components of matrix to another and to surfaces of cells

Question 24

fibronectin

Answer 24

dimeric glycoprotein; principle adhesion protein of connective tissues

Question 25

laminin

Answer 25

principle adhesion protein of basal lamina; a heterotrimer with 3 subunits (alpha, beta, game); contain domains that allow it to bind to itself, cells, collagen, and proteoglycans

Question 26

nidogen

Answer 26

protein that links laminin to collagen type IV

Question 27

agrin

Answer 27

large proteoglycan of ECM

Question 28

integrins

Answer 28

major cell surface proteins responsible for attachment of cells to ECM, anchors the cytoskeleton within the cell and provides linkage between intra and extra matrix, and serve as receptors that activate intracellular signalling pathways in response to signals within ECM

Question 29

integrin domains

Answer 29

cytoskeletal binding in cytoplasm, ECM binding domain and signal receptor domain

Question 30

focal adhesions

Answer 30

a type of cell-matrix junction that attaches a variety of cells, including fibroblasts, to the ECM; this type of integrin binding is reversible

Question 31

hemidesmosomes

Answer 31

strongest type of cell-matrix junction; mediate epithelial cell attachments at which a specific integrin interacts with laminin in the basal lamina

Question 32

integrins link the _____ directly to the ______________

Answer 32

ECM, cytoskeleton

Question 33

focal adhesion vs hemidesmosomes

Answer 33

focal adhesions can be stable but turn over rapidly, hemispheres are very stable and long-term

Question 34

3 categories cell-cell junctions

Answer 34

• stable adhesion junctions
• tight junctions
• gap junctions

Question 35

stable adhesion junction types

Answer 35

adherens junction and desmosome

Question 36

adherens junction

Answer 36

region of c-c adhesion at which actin cytoskeleton is anchored to plasma membrane; involves protein in adjacent cells known as cadherins

Question 37

desmosome

Answer 37

strongest c-c junction; region of adhesion between epithelial cells at which intermediate filaments are anchored to plasma junction

Question 38

tight junctions

Answer 38

ensure any molecules moving across the epithelial cell layer in either direction MUST move through the cell not between cells (therefore, cell can regulate it!!)

Question 39

cadherins

Answer 39

link actin cytoskeleton of adjacent cells

Question 40

desmoglein and desmocollin

Answer 40

a family of cadherins involved in desmosomes that link the cytoskeletons of adjacent cells

Question 41

what separates apical and basal domains of plasma membrane?

Answer 41

tight junctions

Question 42

gap junctions

Answer 42

open channels through plasma membrane that provide direct connection between cytoplasm of adjacent cells and allow for open flow of ions and small molecules (mechanisms to couple metabolic and electrical activity)

Question 43

connexin

Answer 43

transmembrane proteins that form gap junctions

Question 44

connexon

Answer 44

cylinder formed by six connexins in plasma membrane