Cell Junctions and Surface Specializations

Question 1

Two classes of cell adhesion molecules

Answer 1

Calcium dependent; calcium independent

Question 2

Calcium dependent adhesion molecules

Answer 2

Cadherins, selectins

Question 3

Calcium independent adhesion molecules

Answer 3

integrins, immunoglobulin superfamily

Question 4

Function of cadherins

Answer 4

Maintain cell-cell contacts. Primarily homophilic adhesions (binds to other cadherins)

Question 5

How does calcium removal affect cadherins?

Answer 5

Calcium removal stops adhesion and makes cadherins vulnerable to proteases

Question 6

Adhesion using cadherins is stabilized by

Answer 6

actin cytoskeleton (binding to actin via catenins)

Question 7

What is the loss of E-cadh erin associated with?

Answer 7

Tumor metastasis

Question 8

E-cadherin is found in

Answer 8

epithelia

Question 9

N-cadherin is found in

Answer 9

neural cells

Question 10

Selectins

Answer 10

Bind to carbohydrates-each selection has carbohydrate recognition domain (CRD). Important for controlling movement of leukocytes from blood into tissues.

Question 11

P-selectin

Answer 11

platelets, activated endothelial cells

Question 12

E-selectin

Answer 12

activated endothelial cells

Question 13

L-selectin

Answer 13

leukocytes (homing receptor)

Question 14

In selectins, calcium bound at the sides of the CRD regulates

Answer 14

the conformation of the domain and its ability to bind carbohydrates

Question 15

Outside the cell, the binding site on integrin is on what subunit?

Answer 15

β subunit (binds laminin, fibronectin, tenascin, vitronectin, collagen…)

Question 16

Inside cell (Integrin) binds to cytoskeletal actin

Answer 16

via actin binding proteins (talin, vinculin, α-actinin)

Question 17

Adhesion of integrins is stabilized (and destabilized) by

Answer 17

actin cytoskeleton

Question 18

Immunoglobulin Superfamily

Answer 18

share Ig-like domain;

Question 19

HIV-1 receptor(CD4 on lymphocyte) is a member of what family

Answer 19

Immunoglobulin Superfamily

Question 20

Occluding (tight) junctions

Answer 20

prevent free passage across an epithelial layer

Question 21

In occluding junctions, transmembrane occludin interacts with…

Answer 21

claudin

Question 22

Why are tight (occluding) junctions medically important ?

Answer 22

Tight junctions are medically important because it can prevent the delivery of drugs to the bloodstream or tissues

Question 23

Tight junctions determine

Answer 23

epithelial polarity

Question 24

Cell junction which has a “belt-like distribution”

Answer 24

Zonula Adherens

Question 25

Zonula Adherens involves interaction primarily with

Answer 25

cadherins and catenins

Question 26

Desmosomes are stabilized by

Answer 26

intermediate filaments(keratin or vimentin)

Question 27

Desmosomes lack

Answer 27

afadin-nectin and catenin complexes

Question 28

Intercellular “rivets”-spot like junction

Answer 28

desmosomes

Question 29

Hemidesmosomes

Answer 29

anchor basal portion of cell to basal lamina

Question 30

What is the only asymmetrical junction

Answer 30

Hemidesmosomes

Question 31

Anchoring filaments involved in Hemidesmosomes

Answer 31

Laminin 5

Question 32

Communicating junction between cells

Answer 32

Gap junctions

Question 33

Six integral membrane proteins called connexins associate to form a

Answer 33

connexon

Question 34

Gap junctions link cells ________ and _________

Answer 34

chemically and electrically

Question 35

Connexin 26 mutation

Answer 35

deafness

Question 36

Connexin 32 mutation

Answer 36

Charcot-Marie-Tooth neuropathies: progressive peripheral nerve degeneration

Question 37

Connexin 50 mutation

Answer 37

congenital cataracts and blindness

Question 38

Microvilli increase _____ ____ for _________

Answer 38

surface area; absorption

Question 39

Structure of cilia and flagella

Answer 39

9+2 array of highly stable microtubules

Question 40

Cilia

Answer 40

hairlike appendages that move fluid-develop from basal bodies (derived from centrioles)

Question 41

Flagella

Answer 41

propeller for sperm motility (Dyneins provide force for movement)

Question 42

Kartagener’s syndrome

Answer 42

Loss of dynein = ciliary dyskinesia. Poor respiratory clearance and reproductive sterility

Question 43

long branching projections that have an actin core(no microtubules or basal body)

Answer 43

non-motile stereocilia

Question 44

What has the same substructure of microvilli?

Answer 44

Stereocillia