Exam 2 Ch 19

Question 1

What are the 2 main ways cells are bound together

Answer 1

Cell-Cell junctions and the extracellular matrix

Question 2

What are the 2 types of Cell-Cell anchoring junctions

Answer 2

Adherens and Desmosomes

Question 3

What do adherens junctions do

Answer 3

Anchor actin cytoskeleton in cell 1 to the actin cytoskeleton of cell 2

Question 4

What do desmosomes do

Answer 4

Anchor the intermediate filaments in cell 1 to the intermediate filaments of cell 2

Question 5

What are the 2 cell-matrix anchoring junctions

Answer 5

Actin-linked cell matrix and Hemidesmosomes

Question 6

What do Actin-linked cell matrix junctions do

Answer 6

Anchor actin cytoskeleton to the extracellular matrix

Question 7

What do Hemidesmosomes do

Answer 7

Anchor intermediate filaments the extracellular matrix

Question 8

What do cell-matrix anchoring junctions do

Answer 8

Anchor the cytoskeleton of a cell to the extracellular matrix

Question 9

What do Cell-cell anchoring junctions do

Answer 9

anchor the cytoskeleton of one cells to the cytoskeleton of another

Question 10

What do tight junctions do

Answer 10

Seal cells together

Question 11

What do gap junctions do

Answer 11

create channels between two cells that allow for the passage of small molecules and electrical signals

Question 12

What do cadherins do

Answer 12

Link cells together at the cell-cell anchoring junctions

Question 13

Where do cadherins link cells together.

Answer 13

Adherens junctions and desmsomes

Question 14

What are cadherins dependent on for maintaining adhesion

Answer 14

Calcium

Question 15

What kind of binding do cadherins exhibit

Answer 15

Homophilic

Question 16

What is homophilic binding

Answer 16

Like binds to like

Question 17

What side are epitheleial cells anchored to other tissue

Answer 17

Basal side

Question 18

Which side of epithelial cells are free of attachments

Answer 18

Apical

Question 19

What does it mean that tight junctions serve as a selectively permeable barrier

Answer 19

It separates fluid on one side of the cell from fluid on the other side but allow certain molecules through

Question 20

What are the transmembrane proteins that form the tight junctions

Answer 20

Claudins and occludins

Question 21

How do Gap junctions couple the cells

Answer 21

both electrically and metabolically

Question 22

How do gap junctions work

Answer 22

They create a channel between the 2 cells that allows small water-soluble molecules to pass from one cell to the other but not allowing large molecules to passthrough

Question 23

What protein forms the channels for the gap junctions

Answer 23

Connexins which come together to form connexons

Question 24

What is the extracellular matrix made up of and oriented by

Answer 24

The cells within it

Question 25

What do fibroblast do and where are they found

Answer 25

They create alot of extracellular matrix by secreting the macromolecules Commonly found in connective tissue

Question 26

What are the 3 major classes of extracellular matrix macromolecules

Answer 26

GAGs, Fibrous proteins, Glycoproteins

Question 27

Describe GAGs

Answer 27

Resist compressive forces Highly negatively charged Unbranched polysaccharides (repeating disaccharide units)

Question 28

How are GAGs linked to a protein

Answer 28

Via a link tetra-saccharide on a serine residue of the protein

Question 29

What are the 2 types of Fibrous proteins

Answer 29

Collagen and elastin

Question 30

Describe collagens

Answer 30

A major protein in the ECM Form long, stiff triple alpha helical structures Organize in bundles

Question 31

What are collagen fibrils

Answer 31

bundles of collagen

Question 32

What are collagen fibers

Answer 32

Bundles of collagen fibrils

Question 33

What type of collagen do NOT aggregate togehter

Answer 33

Fibril-associated collagens They bind to the surface of fibrils formed by fibrillar collagens instead

Question 34

Describe elastin

Answer 34

Main component of elastic fibers Secreted ito extracellular matrix and assembles into elastic fibers

Question 35

What are the 2 main components of elastin

Answer 35

Hydrophobic segment and Alpha-helical segment

Question 36

What is the hydrophobic segment of elastin used for

Answer 36

the elastic properties

Question 37

What is the of elastin Alpha-helical segment used for

Answer 37

cross link to adjacent molecules

Question 38

describe glycoproteins

Answer 38

Act as a large scaffold with multiple binding sites for other matrix macromolecules Helps organize the ECM and helps cells attach to it

Question 39

What is fibronectin

Answer 39

The best understood glycoprotein Binds to collagen, other proteoglycans, and integrins on cell surface A dimer with 2 very large subunits joined by a disulfide bond at C term

Question 40

Describe the basal lamina

Answer 40

Specialized type of ECM Lies underneath epithelium HAs many roles Primarily made up of 2 EMC macromolecules

Question 41

Roles of Basal lamina

Answer 41

Structural; filtration; determine cell polarity; influence cell metabolism; organize the proteins on adjacent cellular plasma membranes; promote cell survival, proliferation, or differentiation; serve as highways for cell migration

Question 42

What are the two ECM Macromolecules in the basal lamina

Answer 42

Laminin and Type 4 collagen

Question 43

Describe Laminin

Answer 43

A glycoprotein composed of 3 long polypeptide chains held together by disulfide bonds They can self assemble into a network through interactions between their heads

Question 44

Describe Type 4 Collagen

Answer 44

network forming collagen Several isoforms that can twist together to form a ropelike superhelix

Question 45

What do integrins do

Answer 45

Anchor cells to the extracellular matrix

Question 46

Where do integrins link cells

Answer 46

Hemidesmosomes and Actin-linked matrix junctions

Question 47

What do hemidesmosomes do

Answer 47

Anchor intermediate filaments to he extracellular matrix

Question 48

What do actin-linked matrix junctions do

Answer 48

Anchor the actin cytoskeleton of a cell to the extracellular matrix

Question 49

Describe an inactive integrin

Answer 49

External segments are folded and cannot bind to ECM proteins Internal segments cannot interact with cytoskeletal linker proteins

Question 50

Describe active integrins

Answer 50

Conformational change and binding sites are exposed