Cell adhesion

Question 1

What is the function of junctions?

Answer 1

Mediate cell-cell and cell-ECM adhesion
Regulate cell polarity
Involved in intercellular communication

Question 2

What are the 3 main classifications of junctions?

Answer 2

Anchoring
Occluding
Communicating

Question 3

What are anchoring junctions?

Answer 3

Mediate cell-cell and cell-ECM
Attachment

Question 4

What are the types of anchoring junctions?

Answer 4

Adherens junction
Desmosome
Hemidesmosome
Focal contact

Question 5

What is an adherens junctions, its location, and what is its primary protein?

Answer 5

Cell-cell adhesion near apical surface

Cadherin

Question 6

What cytoskeletal component is associated with adherens junction?

Answer 6

Actin

Question 7

What two anchoring junctions support each other and why?

Answer 7

Adherens junction and desmosomes

Resist mechanical stress and maintain tissue integrity

Question 8

What is a desmosome, where is it located, and what are its main proteins?

Answer 8

Strong cell-cell adhesion beneath adherens junctions

Desmosomal cadherins

Question 9

What are the two desmosomal cadherins?

Answer 9

Desmoglein
Desmocollin

Question 10

What cytoskeletal component binds to desmosomes

Answer 10

Intermediate filaments

Question 11

What are hemidesmosomes, where are they located, and what is their primary protein?

Answer 11

Strong adhesion between basal surface of cell and basal lamina

Integrins

Question 12

What cytoskeletal component do hemidesmosomes interact with?

Answer 12

Intermediate filaments

Question 13

What do integrins interact with in the basal lamina?

Answer 13

Laminin and Collagen

Question 14

What are focal contacts and what is their function?

Answer 14

Between cell’s basal surface and ECM

Adhesion of cell to substratum

Question 15

What is their primary protein and there cytoskeleton partner?

Answer 15

Integrins

Actin

Question 16

What is the main occluding junction?

Answer 16

Tight junctions

Question 17

What is the function of a tight junction?

Answer 17

Forms seal at that separates luminal/apical surfaces from intercellular space and basal surface

Question 18

What are the main proteins associated with tight junctions?

Answer 18

Claudin
Occludin
ZO

Question 19

What is the cytoskeletal partner of tight junctions?

Answer 19

Actin

Question 20

What are the functions of tight junctions in epithelia cells?

Answer 20

Forms seal between adjacent epithelial cells
Regulates selective diffusion of hydrophilic molecules through paracellular space
Restricts migration of membrane proteins
Maintains cell polarity

Question 21

What is the main communicating junction?

Answer 21

Gap junctions

Question 22

What are the characteristics of a gap junction?

Answer 22

Hydrophilic channel formed of 2 connexons between two cells
Connexons are composed of connexin

Question 23

What is the function of gap junctions?

Answer 23

Intercellular communication
Direct exchange of small metabolites and signaling molecules between adjacent cells

Question 24

What are the four major families of cell adhesion molecules (CAMs) and what type of junction are they associated with?

Answer 24

Cadherin
Immunoglobulin
Integrin
Selectin

Anchoring junctions

Question 25

What are the characteristics of cadherins?

Answer 25

Primary family Homophilic Cell-cell adhesion Bind catenins that bind actin Ca++ dependent

Question 26

What are the characteristics of immunoglobulin super family of CAMs?

Answer 26

Homophilic and heterophilic (with self or integrins) Mainly cell-cell ICAM and VCAM adhesion molecules bind actin

Question 27

What are the characteristics of integrins?

Answer 27

Cell to cell or cell-ECM Can bind actin and intermediate filaments

Question 28

What are the characteristics of selectins?

Answer 28

Heterophilic Cell-cell in bloodstream Bind carbohydrates Bind to actin

Question 29

What is the major function of selectins?

Answer 29

Initiating adhesion of leukocytes and platelets to endothelial cells during inflammation and hemostasis

Question 30

What is the function of matrix metalloproteinases (MMPs)?

Answer 30

Degrade ECM

Question 31

What is the function of ECM?

Answer 31

Structure Shape, strength and elasticity to tissues Substratum for adhesion Signal transduction Reservoir for growth factors

Question 32

What is the main ECM protein family?

Answer 32

Collagen

Question 33

What is the function of collagen?

Answer 33

Tensile strength and stability

Question 34

What is the basement membrane?

Answer 34

Highly cross-linked layer of ECM that anchors epithelial cells to connective tissue

Question 35

What are the functions of the basement membrane?

Answer 35

Compartmentalizes tissues Physical barrier to macromolecules Cell shape and polarity

Question 36

What is laminin and what is its function?

Answer 36

Major component of basement membrane Helps mediate hemidesmosomal attachment

Question 37

What are glycosaminoglycans (GAGs)?

Answer 37

Long carbohydrate changes with anionic groups Most are proteoglycans - linked to polypeptide core

Question 38

What are types of GAGs?

Answer 38

Hyaluronic acid Chondroitin sulfate Dermatan sulfate Keratan sulfate Heparan sulfate

Question 39

What is the function of GAGs?

Answer 39

Resist compressive forces Hold H2O

Question 40

What is ground substance?

Answer 40

Matrix of loose connective tissue made of proteoglycans

Question 41

What are elastic fibers and their main components?

Answer 41

Form network with interwoven collagen Elastin and fibrillin

Question 42

What is the function of elastic fibers?

Answer 42

Allow recoil of stretched tissue, provide elacticity

Question 43

What is fibronectin?

Answer 43

Adhesion glycoprotein that attaches cells to other ECM components via integrins

Question 44

What is fibrinogen?

Answer 44

Protein component of blood clots that can connect with integrins and fibronectin

Question 45

How is fibrin made?

Answer 45

Cleavage of fibrinogen by thrombin