Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Molecular Test III > Lecture 19 Cell Junctions, Cell Adhesion, and the Extracellular Matrix 1&2 > Flashcards

Lecture 19 Cell Junctions, Cell Adhesion, and the Extracellular Matrix 1&2 Flashcards

1
Q

Anchoring junctions

A

Cell-cell adhesions and cell-matrix adhesion, and are connected to cytoskeletal filaments inside the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Occluding junctions

A

seal gaps between epithelial cells so as to make the epithelial sheet into an impermeable barrier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Channel-forming junctions

A

create passageways for small molecules and ions to pass from cell to cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Signal-relaying junctions

A

Allow signals to be relayed from cell to cell across their plasma membranes at cell-to-cell contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Cadherins have what type of binding?

A

homophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Integrins have what type of binding?

A

Heterophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe classical cadherin

A

Main mediators of Calcium dependent adherens junctions
also important for signaling

intracellular cytoskeletal attachement are actin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe non classical cadherins

A

Desmosome junction cell to cell interaction. Used intermediate filaments for cytoskeletal attachement.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are some types of classical cadherins?

A

E-, N-, VE-, P-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are some types of nonclassical cadherins?

A

Desmocollins, desmogleins that form desmosome junctions

Protocadherins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What makes cadherins “sticky”

A

Cadherin domain motif

All cadherins have extracellular portions that contain multiple copies of cadherin domain motif

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What end does homophilic binding occur on cadherin molecules?

A

N-terminal tips

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What prevents the string of cadherin domains from flexing, and keeps it as a rigid rod?

What if it isnt present?

A

Ca ions bind to sites near each hinge and prevents the string from bending
When Ca is removed, the hinges can flex, and the structure becomes floppy. The N terminus changes and weakens the binding affinity and disrupts the adhesion.
Cadherins are then degraded.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The formation of strong attachments to other cadherins results from what?

A

Cadherins typically bind to their partners with relatively low affinity but many weak bonds in parallel functions like a Velcro to hold cells together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What links classical cadherins to actin filaments?

A

Intracellular anchor proteins that assemble on the tail of the cadherin.

CATENIN!!!

These proteins include β-catenin, p120-catenin, and γ-catenin (plankoglobin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are an essential part of the machinery for modeling the shape of multicellular structures?

A

Adherens junctions

Often form a continuous adhesion belt close beneath the apical face of the epithelium, encircling each of the interacting cells in the sheet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What lies adjacent to the adhesion belt, oriented parallel to the plasma membrane and tethered to it by the cadherins and their associated intracellular anchor proteins?

A

Contractile bundle of actin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the first junction that is formed

A

cadherins = adherens junctions connected to the actin cytoskeleton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What cadherins forms spot well junctions in the formation in a synapse?

A

N-cadherins

allows flexibility at the synaptic cleft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

E or N cadherins promotes migration?

A

N cadherins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is similar between adherens junction and desmosomes?

A

Use cadherins

Use catenins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the difference between adherens junction and desmosome?

A

Classical cadherins and non classical cadherins

Major difference is the cytoskeletal attachment differences!!!!!
By using intermediate filaments, desmosomes can have a stronger mechanical strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Bundle of intermediate filaments that are anchored to the desmosomes form a structure framework with what characteristic?

A

Great tensile strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the structure of a desmosome?

A

Keratin intermediate filaments
Dense plaque of anchor proteins
Cadherins - Ca dependent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What are the desmosomal cadherins?
desmoglein and desmocollin | *homophilic and heterophilic binding
26
What is a desmosome mutation?
ARVC | sudden cardiac death in the young
27
Tight junction
Occluding junctions found in epithelia and endothelial sheet Forms a seal between cells Forms a fence between membrane domains Recruits cytoskeleton as well as signaling molecules
28
Structure of tight junctions
Branching network of sealing strands Focal connections Proteins: claudin (main component) and occludin *4 pass transmembrane JAMs homophilic adhesions
29
What type of junctional complexes can be found in mature epithelium?
Tight junction, adherens junction, and desmosome
30
The positioning and organization of junctions in tight junctions in relation to other structures depends on the association with what proteins?
Intracellular scaffold protein of the Tip family also called ZO protein. ZO anchors tight junctions to actin cytoskeleton
31
What are three proteins that control polarization processes and maintain polarity?
Par, Crumbs, and Scribble
32
Describe how epithelial cell polarity is established
Adherens junction forms and recruits Par complex. Immediately signals to start placing tight junctions proteins right above it Then that signals the crumbs complex to stabilize the tight junctions Scribble comes in later for cytoplasmic proteins
33
Gap junctions
Made up of connexins Create a pore complex that allows things to pass between. Channel-forming proteins Couples cells both electrically and metabolically Only small water-soluble molecules (mostly ions and glucose)
34
Describe the hemichannel connexons in gap junction
Hexameric: consist of 6 connexin protein subunits Connexins are 4 pass tmp
35
A connexon can be made up of what subunits?
Homohexameric (same) or heterohexameric (different) subunits Most cell types express more than one type of connexin Humans have 14 Adjacent cells expressing different connexins can form intercellular channels in which two different join forming heterotypic
36
Functions of GAP junctions
allow action potentials to spread rapidly from cell to cell Syncrhonizes the contractions of heat and smooth muscle cells Sharing small metabolites and ions by gap junctions-proiveds coordination
37
Individual gap-junction channels do not remain continuously open True or False?
True; instead they flip between open and closed states
38
What causes gap junction channels to close immediately?
Large influx of Ca into the damaged cell
39
Describe building of Gap Junction
Each gap-junctional plaque can readily assemble or disassemble. New connexons are continually added, and old removed and destroyed
40
What neurotransmitter reduces gap-junction communication between a class of neurons in the retina in response to an INCREASE in light intensity?
dopamine Helps the retina switch from rod to cone
41
Blue represents what filament?
intermediate
42
Red represents what filament?
Actin
43
What layer underlies all epithelia?
basal lamina
44
Functions of basal lamina?
Separates cells from connective tissue Selective filter Determine cell polarity Influence metabolism Organize proteins in adjacent plasma membrane Promotes cell survival, proliferation or differentiation Solid surface
45
Lamina consists of what two main classes of extracellular macromolecules?
Fibrous protein: glycoproteins | Glycosaminoglycan: proteoglycans
46
What are the compoents of basal lamina?
laminin, type IV collagen
47
What is the primary organizer of the sheet structure of basal lamina?
Laminin: | Cross like structure made up of three polypeptides chains
48
Type IV collagen
Three long protein chains that twist together to form a rope-like superhelix Terminal domains interact to assemble network Provide tensile strength
49
What does an integrin molecule consists of?
alpha and beta subunits noncovalently associated Short C-terminal tails Large N terminal extra-cellular domains
50
What is intracellular linkage to actin mediated by?
Talin and a set of other anchorage proteins
51
What are cell-matrix attachment sites where specific type of integrin anchors the cells to laminin in the basal lamina?
Hemidesmosomes
52
If the integrin is attached to keratin filaments, is it more likely to move or be fixed?
Fixed
53
Contact that integrins make are often called what?
focal adhesions
54
Describe outside-in activation and inside-out activation.
Outside-in: ligand attaches causing conformational change, pulls apart to allow talin to be exposed (intracellular). actin filaments assemble Inside-out: talin brought to beta tail; breaks alpha and beta bond-activates conformation
55
For cell to bind strongly to extracellular matrix requires interaction of clustering integrins. When the transmembrane portion of each type of subunit interacts with itself this is called:
homotypic oligomerization
56
Integrins activate intracellular signaling pathways, the major protein involved is:
FAK: focal adhesion kinase | Src/FAK complex
57
What does FAK promote?
cytoskeleton fluidity | Normally it helps to dissemble focal adhesions
58
In most connective tissues, the matrix macromolecules are secreted largely by cells called what?
fibroblasts
59
What are the two main classes of extracellular macromolecules that make up the matrix?
GAGs (creates squishiness-gel like structure) and fibrous proteins
60
GAGs:
usually covelently linked to protein in the form of proteoglycans forms highly hydrated, gel-like ground substance in which fibrous proteins are embedded Provide mechanical support to tissue; withstand compressive forces
61
What always comes off of the serine in a core protein in proteoglycans?
tetrasaccharide: serves as a primer for polysaccharide growth
62
What are the four major types of glycoaminoglycans?
Chondrioitin sulfate, Dermatan sulfate Heparan sulfate Keratan sulfate
63
Sugar chains that come off of proteoglycans are always in ____
pairs of disaccarides
64
Chondroitin 6-sulfate Glucuronic acid Glucosamine
give it to arthritic people | important components of proteoglycans
65
Hyaluronic acid
Biggest part of proteoglycans (hyaluronic acid) composed of glucosamine and glucuronic acid
66
What can be directly bound to proteoglycans that stimulate a variety of cell types to proliferate?
FGFs: fibroblast growth factors
67
What are the most abundant protein in the body?
collagens | Major component of skina nd bone
68
Describe collagens
Extremely rich in proline and glycine (helical structures and flexibility) Long, stiff, triple-stranded helical structure Proline forms alpha chain Glycine allows alpha chain to pack tightly together Left-handed helix Twist to the left but three chains together twist right Synthesized in the ER; secreted by fibroblast
69
Type 1 collagen makes up how much of the collagen in the body?
90%
70
Collagen diseases
Scurvy: lack of vitamin C | Ehlers-Danlos VI: defective enzyme-loose tissue bc of OH groups

Molecular Test III (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions