04c: Cell Surface Specialization

Question 1

Apical cell surface specializations.

Answer 1

1. Cilia
2. Stereocilia
3. Microvilli

Question 2

Lateral cell surface specializations.

Answer 2

1. Junctions (occluding, adhering, communicating)

2. Membrane plicae (infoldings)

Question 3

Basal cell surface specializations.

Answer 3

Basal lamina and basal striations

Question 4

List the principal elements of cytoskeleton. Which are intracellular/Extracellular?

Answer 4

1. Microfilaments
2. MT
3. Intermediate filaments

All intracellular!

Question 5

Which key filament supports microvilli?

Answer 5

Bundle of actin filaments

Question 6

At base of microvilli, which structure serves as support?

Answer 6

Terminal web of actin filaments

Question 7

The (X) of the cell’s microvilli reflect the cell’s (Y) capacity.

Answer 7

X = shape and number
Y = absorptive

Question 8

Choroid plexus has which cell specialization?

Answer 8

Stubby microvilli (allow absorption of CSF to subarachnoid space)

Question 9

Cilia and (X) have which special characteristic of movement?

Answer 9

X = flagella

Rhythmic, coordinated beating

Question 10

Core of cilium is called (X). Describe structure.

Answer 10

X = axoneme

(9+2) Complex of MT and MAPs

Question 11

Which protein involved in movement in cilia?

Answer 11

Dynein

Question 12

Snapping movement of cilium is controlled by (X), which is composed of:

Answer 12

X = basal body

Short cylinder of 9 MT triplets

Question 13

T/F: basal body of cilium is located within the cell.

Answer 13

True

Question 14

Stereocilia function.

Answer 14

Absorption

Question 15

Which protein involved in movement in stereocilia?

Answer 15

Stereocilia are non-motile

Question 16

Stereocilia structure

Answer 16

Long, branches core of actin filaments

Question 17

T/F: intercellular junctions are only really found in Epithelia.

Answer 17

False

Question 18

Subcategories of intercellular junctions.

Answer 18

1. Occluding
2. Adhering
3. Communicating

Question 19

List subtypes of occluding intercellular junctions.

Answer 19

Zonula occludens

Question 20

List subtypes of adhering intercellular junctions.

Answer 20

1. Zonula adherens
2. Macula adherens
3. Fascia adherens
4. Hemidesmosome

Question 21

List subtypes of communicating intercellular junctions.

Answer 21

Gap junctions

Question 22

“Zonula” indicates:

Answer 22

A “belt” around cells

Question 23

“Macula” indicates:

Answer 23

A distinct spot of adhesion between cells

Question 24

“Fascia” indicates:

Answer 24

A sheet-like structure that stabilizes cells

Question 25

Tight junctions, aka (X), function to:

Answer 25

X = zonula occludens 1. Limits passage of material between adjacent cells 2. Keeps apical and basolateral membrane domains separate

Question 26

Which proteins form stitches in zonula occludens?

Answer 26

1. Occludins | 2. Claudins

Question 27

Proteins involved in forming zonula occludens are present on (intra/extra)-cellular side of membranes.

Answer 27

They're multi-pass transmembrane proteins

Question 28

T/F: zonula occludens proteins are impermeable to all molecules.

Answer 28

False - Claudins are permeable to water

Question 29

Leakiness of zonula occludens depends on:

Answer 29

1. Tightness of transmembrane particle "quilt pattern" | 2. Relative amount of claudins

Question 30

(X) prevents cell rupture when sheet of cells stretch. How?

Answer 30

X = Adhering junctions Transmembrane proteins attach cytoskeletal filaments of one cell to those of adjacent cells

Question 31

Zonula adherens, aka (X), specifically links:

Answer 31

X = intermediate junctions Cadherin complex and actin to that of adjacent cell

Question 32

Zonula adherens are typically found closer to (apical/middle/basal) part of cells.

Answer 32

Apical (near lumen)

Question 33

(X) intercellular junctions are Ca-dependent.

Answer 33

X = zonula and macula adherins

Question 34

Macula adherens, aka (X), are (weaker/stronger) than zonula adherens.

Answer 34

X = desmosomes Much stronger

Question 35

Describe structure of macula adherens.

Answer 35

Dense attachment plaque with transmembrane proteins that associate with those of adjacent cell

Question 36

Transmembrane proteins, such as (X), involved in macula adherens are which type of proteins?

Answer 36

X = desmocollin and desmoglein Glycoproteins

Question 37

Which type of cytoskeletal component associates with (X) in the macula adherens?

Answer 37

X = attachment plaque Loops of bundled keratins (intermediate filaments)

Question 38

The dense attachment plaque, found in (X) intercellular junctions, is located (intra/extra)-cellularly.

Answer 38

X = macula adherens Intracellular

Question 39

(X) junctions, with (Y) cytoskeletal components, link the epithelial cells of the skin.

Answer 39

``` X = desmosomes Y = keratin filaments ```

Question 40

The junctional complex is crucial for:

Answer 40

Epithelia's effective barrier function

Question 41

The junctional complex is which type of intercellular junction?

Answer 41

Consists of: 1. Tight junction 2. Intermediate junction 3. Desmosome

Question 42

(X) corresponds to the terminal bar of LM.

Answer 42

X = junctional complex

Question 43

What the plicae in the (X) membrane?

Answer 43

X = lateral Infoldings to increase surface area

Question 44

Hemidesmosome is located on which surface of epithelial cell?

Answer 44

Basal

Question 45

Hemidesmosome links:

Answer 45

Cytoskeletal intermediate filaments to transmembrane integrins (which links epithelium to basement membrane)

Question 46

Gap junction, aka (X), formed by which protein(s)?

Answer 46

X = nexus 6 transmembrane connexins form aqueous pore (transmembrane cylindrical connexons)

Question 47

(X) intercellular junctions can open/close, permitting passage of (Y).

Answer 47

X = gap junctions Y = small molecules (less than 1 kD)

Question 48

T/F: Ligands and signal molecules regulate opening/closing of gap junctions.

Answer 48

False - voltage

Question 49

Gap junctions are incredibly important for:

Answer 49

Intercellular coordination/communication

Question 50

Transportation of ions from lumen to underlying connective tissue depends on which specific proteins in (X) membrane/surface of epithelium?

Answer 50

X = basal Na/K pumps

Question 51

(X) increase surface area of basal membrane.

Answer 51

X = Basal enfoldings

Question 52

Why would there be so many of (X) organelle around (Y) enfoldings?

Answer 52

``` X = mitochondria Y = basal ``` To provide ATP for Na/K pumps

Question 53

EM image: dark spots in plasmolema indicate what?

Answer 53

Spots where actin associates with integrin

Question 54

The protein (X) is important in linking extracellular domain of integrin to (Y) in basal lamina.

Answer 54

``` X = laminin Y = Type 4 collagen ```

Question 55

What's the difference, if any, between basal lamina and external lamina?

Answer 55

Same morphology and functions, but different locations

Question 56

External lamina found in (X) cells.

Answer 56

X = Schwann, muscle, fat

Question 57

Zonula adherens have which type of transmembrane protein linking adjacent cell (X) cytoskeleton component.

Answer 57

Cadherin; X = actin