04c: Cell Surface Specialization Flashcards
Apical cell surface specializations.
- Cilia
- Stereocilia
- Microvilli
Lateral cell surface specializations.
- Junctions (occluding, adhering, communicating)
2. Membrane plicae (infoldings)
Basal cell surface specializations.
Basal lamina and basal striations
List the principal elements of cytoskeleton. Which are intracellular/Extracellular?
- Microfilaments
- MT
- Intermediate filaments
All intracellular!
Which key filament supports microvilli?
Bundle of actin filaments
At base of microvilli, which structure serves as support?
Terminal web of actin filaments
The (X) of the cell’s microvilli reflect the cell’s (Y) capacity.
X = shape and number Y = absorptive
Choroid plexus has which cell specialization?
Stubby microvilli (allow absorption of CSF to subarachnoid space)
Cilia and (X) have which special characteristic of movement?
X = flagella
Rhythmic, coordinated beating
Core of cilium is called (X). Describe structure.
X = axoneme
(9+2) Complex of MT and MAPs
Which protein involved in movement in cilia?
Dynein
Snapping movement of cilium is controlled by (X), which is composed of:
X = basal body
Short cylinder of 9 MT triplets
T/F: basal body of cilium is located within the cell.
True
Stereocilia function.
Absorption
Which protein involved in movement in stereocilia?
Stereocilia are non-motile
Stereocilia structure
Long, branches core of actin filaments
T/F: intercellular junctions are only really found in Epithelia.
False
Subcategories of intercellular junctions.
- Occluding
- Adhering
- Communicating
List subtypes of occluding intercellular junctions.
Zonula occludens
List subtypes of adhering intercellular junctions.
- Zonula adherens
- Macula adherens
- Fascia adherens
- Hemidesmosome
List subtypes of communicating intercellular junctions.
Gap junctions
“Zonula” indicates:
A “belt” around cells
“Macula” indicates:
A distinct spot of adhesion between cells
“Fascia” indicates:
A sheet-like structure that stabilizes cells
Tight junctions, aka (X), function to:
X = zonula occludens
- Limits passage of material between adjacent cells
- Keeps apical and basolateral membrane domains separate
Which proteins form stitches in zonula occludens?
- Occludins
2. Claudins
Proteins involved in forming zonula occludens are present on (intra/extra)-cellular side of membranes.
They’re multi-pass transmembrane proteins
T/F: zonula occludens proteins are impermeable to all molecules.
False - Claudins are permeable to water
Leakiness of zonula occludens depends on:
- Tightness of transmembrane particle “quilt pattern”
2. Relative amount of claudins
(X) prevents cell rupture when sheet of cells stretch. How?
X = Adhering junctions
Transmembrane proteins attach cytoskeletal filaments of one cell to those of adjacent cells
Zonula adherens, aka (X), specifically links:
X = intermediate junctions
Cadherin complex and actin to that of adjacent cell
Zonula adherens are typically found closer to (apical/middle/basal) part of cells.
Apical (near lumen)
(X) intercellular junctions are Ca-dependent.
X = zonula and macula adherins
Macula adherens, aka (X), are (weaker/stronger) than zonula adherens.
X = desmosomes
Much stronger
Describe structure of macula adherens.
Dense attachment plaque with transmembrane proteins that associate with those of adjacent cell
Transmembrane proteins, such as (X), involved in macula adherens are which type of proteins?
X = desmocollin and desmoglein
Glycoproteins
Which type of cytoskeletal component associates with (X) in the macula adherens?
X = attachment plaque
Loops of bundled keratins (intermediate filaments)
The dense attachment plaque, found in (X) intercellular junctions, is located (intra/extra)-cellularly.
X = macula adherens
Intracellular
(X) junctions, with (Y) cytoskeletal components, link the epithelial cells of the skin.
X = desmosomes Y = keratin filaments
The junctional complex is crucial for:
Epithelia’s effective barrier function
The junctional complex is which type of intercellular junction?
Consists of:
- Tight junction
- Intermediate junction
- Desmosome
(X) corresponds to the terminal bar of LM.
X = junctional complex
What the plicae in the (X) membrane?
X = lateral
Infoldings to increase surface area
Hemidesmosome is located on which surface of epithelial cell?
Basal
Hemidesmosome links:
Cytoskeletal intermediate filaments to transmembrane integrins (which links epithelium to basement membrane)
Gap junction, aka (X), formed by which protein(s)?
X = nexus
6 transmembrane connexins form aqueous pore (transmembrane cylindrical connexons)
(X) intercellular junctions can open/close, permitting passage of (Y).
X = gap junctions
Y = small molecules (less than 1 kD)
T/F: Ligands and signal molecules regulate opening/closing of gap junctions.
False - voltage
Gap junctions are incredibly important for:
Intercellular coordination/communication
Transportation of ions from lumen to underlying connective tissue depends on which specific proteins in (X) membrane/surface of epithelium?
X = basal
Na/K pumps
(X) increase surface area of basal membrane.
X = Basal enfoldings
Why would there be so many of (X) organelle around (Y) enfoldings?
X = mitochondria Y = basal
To provide ATP for Na/K pumps
EM image: dark spots in plasmolema indicate what?
Spots where actin associates with integrin
The protein (X) is important in linking extracellular domain of integrin to (Y) in basal lamina.
X = laminin Y = Type 4 collagen
What’s the difference, if any, between basal lamina and external lamina?
Same morphology and functions, but different locations
External lamina found in (X) cells.
X = Schwann, muscle, fat
Zonula adherens have which type of transmembrane protein linking adjacent cell (X) cytoskeleton component.
Cadherin;
X = actin
