Cell Adhesion Molecules and Junctional Complexes

Question 1

What is the basement membrane?

Answer 1

It separates the epithelial layer from connective tissue and consists of the basal and reticular lamina.

Question 2

What is the basal lamina?

Answer 2

The layer of the basement membrane in contact with epithelial tissue. It is produced by the epithelium and contains collagen and other glycoproteins.

Question 3

What is the reticular lamina?

Answer 3

The layer of the basement membrane under the basal lamina. It contains type III collagen.

Question 4

What are some components of the basal lamina?

Answer 4

laminin, fibronectin, type IV collagen, entactin and proteoglycans.

Question 5

What produces type IV collagen?

Answer 5

epithelial cells.

Question 6

What is laminin?

Answer 6

the major component of the basal lamina; it has binding sites for integrins, type IV collagen, entactin and proteoglycans.

Question 7

What is fibronectin?

Answer 7

A protein made up of two polypeptide chains cross-linked by disulfide bonds. It can be cellular or plasma and has binding sites for heparin, integrins, collagen and fibrin.

Question 8

What are the two types of cell-adhesion molecules?

Answer 8

calcium independent and calcium dependent.

Question 9

What are the calcium dependent CAMs?

Answer 9

cadherins and selectins

Question 10

What are the calcium independent CAMs?

Answer 10

integrins and immunoglobulin superfamily molecules.

Question 11

What do cadherins join?

Answer 11

the internal cytoskeleton of a cell and the exterior of another cell.

Question 12

What do adherins join?

Answer 12

The internal cytoskeleton of a cell and the extracellular matrix.

Question 13

Where are E-cadherins found?

Answer 13

epithelial tissue

Question 14

What do E-cadherins form, and where are they found?

Answer 14

dimers that bind to calcium; they are found at the tip of extracellular end of cadherin molecule.

Question 15

What is the function of E-cadherin?

Answer 15

maintenance of most epithelial layers; it relies of calcium to do so or else the cells will break down.

Question 16

What are catenins?

Answer 16

small group of proteins that link the cytoplasmic end of a cadherin with actin.

Question 17

What is the function of cadherins?

Answer 17

To mediate a link with actin, interact with regulatory molecules of actin cytoskeleton and to control adhesive state of EC domain of cadherins.

Question 18

Catenins are the major interface between what two things?

Answer 18

Cadherins that hold adjacent cells together and the actin cytoskeletons of the cells.

Question 19

What are selectins?

Answer 19

calcium dependent CAMs that bind to carbohydrates (receptor is for a specific one).

Question 20

What family do selectins belong to?

Answer 20

lectin (group that binds carbohydrates).

Question 21

What are selectins involved in?

Answer 21

The movement of leukocytes from blood to tissues.

Question 22

What are the classes of selectins?

Answer 22

P-selectins (platelets/immune response), E-selectins (endothelial cells); L-selectins (leukocytes).

Question 23

What are integrins?

Answer 23

Glycoproteins that are mainly involved in cell-extracellular matrix interactions.

Question 24

Where do integrins bind?

Answer 24

to the extracellular matrix and the cytoskeleton (fibrin and laminin).

Question 25

What CAM molecules does integrin bind to in the cytoskeleton?

Answer 25

Fibronectin and laminin

Question 26

What do laminin and fibronectin interact with?

Answer 26

Collagen, heparan, entactin

Question 27

What are immunoglobulins?

Answer 27

calcium-INdependent CAM; it is the extracellular segment of a CAM.

Question 28

What are the five types of junctional complexes?

Answer 28

adherens, occludens, gap junctions, zonula and macular

Question 29

What are adherens?

Answer 29

junctional complex that anchors cells together and reinforces the physical integrity of tissues. They are found on the basolateral surfaces.

Question 30

What are occludens?

Answer 30

junctional complex that establishes impermeable barriers between adjacent cells to prevent transport and maintain concentration differences.

Question 31

What are zonula?

Answer 31

junctions (either adherens or occludens) that line the circumference of a cell and link all neighboring cells to a central cell.

Question 32

What are macula?

Answer 32

junctions (adherens) that are like "spots" that are between the basolateral OR basal domains of cells.

Question 33

What are desmogleins?

Answer 33

cahderin proteins in the junctions (adherens). They are found in the epidermis. They are linked to the cytoplasm via desmoplakin and plakoglobin.

Question 34

What are zonula adherens?

Answer 34

Associated with actin microfilaments.

Question 35

What are the macula dherens?

Answer 35

associated with intermediate filaments (tonofilaments).

Question 36

What are hemidesmosomes?

Answer 36

Anchoring unctions that anchor the basal domain of the pithelial cell to the basal lamina.

Question 37

What is the zonal occludens?

Answer 37

A belt-like junction that prevent paracellular transport.

Question 38

What are tight junctions?

Answer 38

circumferential belts at the apical domain of epithelial cells and linking adjacent endothelial cells.

Question 39

What are focal adhesions?

Answer 39

Spots that anchor the cell to the extracellular mateix via integrins.

Question 40

How are adhesions different from desmosomes?

Answer 40

Adhesions attach to actin filaments via connecting proteins and desmosomes attach to tonofilaments, such as keratin.

Question 41

What are gap junctions?

Answer 41

A communicating junction that allows cells to directly communicate. They are composed of connexons.

Question 42

What are connexons?

Answer 42

They are what gap junctions are composed of. They facilitate movement of molecules.

Question 43

When do gap junctions close?

Answer 43

When calcium concentrations are high.

Question 44

What is the function of a gap junction?

Answer 44

regulate calcium concentration, chemical and electrical coupling.