Cytoskeleton

Question 1

what is the function of the ECM

Answer 1

support and organize cells

Question 2

what are the 2 major macromolecules of the ECM

Answer 2

proteins and polysaccharides

Question 3

adhesive proteins of ECM

Answer 3

fibronectin and laminin

Question 4

function of fibronectin and laminin

Answer 4

adhere ECM components together and to the cell surface

Question 5

structural proteins of ECM

Answer 5

collagen and elastin

Question 6

collagen

Answer 6

provides tensile strength

Question 7

elastin

Answer 7

provides elasticity

Question 8

most abundant protein in the animal kingdom

Answer 8

collagen

Question 9

what does all collagen have in common?

Answer 9

a triple helix structure

Question 10

collagen synthesis

Answer 10

1) procollagen peptide is translated into the ER
2) post-translational modifications
3) self-assembly into triple helix by disulfide bond formation in C-terminus
4) transported in a large specialized vesicle to Golgi
5) more post-translational modifications
6) secreted from cell in specialized vesicles
7) fiber assembly occurs in the extracellular space
8) cleavage of propeptides
9) many triple helices form a fibril
10) fibrils associate to form a fiber

Question 11

laminin

Answer 11

provides an adhesive substrate for cells and to resist tensile forces in tissues

Question 12

the most abundant polysaccharide in animal ECM

Answer 12

glycosaminoglycans (GAGs)

Question 13

structure of GAGs

Answer 13

long unbranched polysaccharides with a repeating disaccharide unit

Question 14

chemical structure of GAGs

Answer 14

highly negative charge on the repeating disaccharide unit attracts positive ions and water (forms a gel like component found in cartilage, skin, eyes, joint fluid)

Question 15

tight junctions

Answer 15

holds adjacent cells together in a layer that prevents leakage of materials between cells (forms tight seal between adjacent cells and prevents the ECM from leaking between cells)

Question 16

gap junctions

Answer 16

channels that permit direct exchange of ions and small molecules between the cytosols of neighboring cells (small gap between plasma membranes of cells at junction; allow adjacent cells to share metabolites and directly signal each other)

Question 17

anchoring junctions

Answer 17

hold cells to each other and/or to the ECM; structurally strong

Question 18

proteins in tight junctions

Answer 18

occludin and claudin

Question 19

proteins in gap junctions

Answer 19

connexon

Question 20

proteins in anchoring junctions

Answer 20

the cell adhesion molecules cadherin and integrin (anchoring junctions rely on CAMs)

Question 21

4 categories of CAMs

Answer 21

adherins junctions, desmosomes, hemidesmosomes, focal adhesions

Question 22

adherins junctions

Answer 22

a family of related cell surface domains that link neighboring cells together

Question 23

structure of adherins junctions

Answer 23

transmembrane cadherin receptors and link the cell’s actin cytoskeletons together

Question 24

desmosomes

Answer 24

intermediate filaments based cell adhesion complexes

Question 25

function of desmosomes

Answer 25

provide structural integrity to sheets of epithelial cells by linking the intermediate filament networks of cells (are also signal transducing complexes!!!)

Question 26

hemidesmosomes

Answer 26

attach epithelial cells to the basal lamina where they link the ECM to the intermediate filament network via transmembrane receptors

Question 27

common feature of desmosomes and hemidesmosomes

Answer 27

both provide structural stability to epithelial sheets

Question 28

cadherin

Answer 28

establishes and maintains cell-cell adhesion complexes ; regulate intracellular signaling by forming a cytoskeletal scaffold that organizes signaling proteins; essential for tissue morphogenesis

Question 29

homophilic binding

Answer 29

by expressing only certain types of cadherins, each cell will only bind to the other expressing the same type of cadherin (important in establishing specific tissues/organs)

Question 30

integrins

Answer 30

connect cells to the ECM (extracellular portion binds to ECM and intracellular portion binds cytoskeleton and signaling proteins) and receptors participate in cell signaling

Question 31

what processes regulate the strength of integrin binding to ECM proteins?

Answer 31

affinity and avidity modulation

Question 32

avidity modulation

Answer 32

strength of adhesion depends on the NUMBER of receptors; varies the clustering of receptors; the accumulated strength of multiple affinities (ex: 10 weak binding sites as opposed to 2 strong binding sites)

Question 33

affinity modulation

Answer 33

strength of adhesion depends on receptor CONFORMATION; varies the binding strength of individual receptors

Question 34

inside out signaling

Answer 34

changes in integrin receptor conformation results from intracellular signals that originate elsewhere in the cell

Question 35

integrin based adhesion complex

Answer 35

integrins are not enzymes, so they associate with adaptor proteins that link them to signaling proteins; complexes have different structures and signaling functions