CAM

Question 1

specialized structures that form physical connections between cells or between a cell and the extracellular matrix (ECM)

Answer 1

junctional adhesion mechanisms

Question 2

located on the lateral surfaces of cells and help hold neighboring cells together

Answer 2

cell-cell adhesion structures

Question 3

these connect cells to the basal laminate or ECM

Answer 3

cell-matrix adhesion structures

Question 4

involve adhesion molecules that mediate looser or more transient interactions and are not part of specialized junctions

Answer 4

non-junctional adhesion mechanisms

Question 5

junctional adhesion mechanisms and cell-cell adhesion structures

Answer 5

1. tight junctions (claudins)
2. adhesion belt (cadherins)
3. desmosomes (cadherins)
4. gap junctions (connexins)

Question 6

junctional adhesion mechanisms and cell-matrix adhesion structures

Answer 6

1. hemidesmosomes (integrins)
2. focal adhesions (integrins)

Question 7

non-junctional adhesion mechanisms

Answer 7

1. cadherins
2. Ig-like CAMs
3. integrins
4. selectins
5. integral membrane
6. proteoglycans

Question 8

type of cell adhesion molecules (CAM)

Answer 8

homophilic interactions
1. cadherins (E-cadherin)
2. Ig-superfamily CAMs (NCAM)

heterophilic interactions
1. integrins (avB3)
2. selectins (p-selectin)

Question 9

function of cadherins

Answer 9

• Mediate Ca2+-dependent cell-cell adhesion
• Cause compaction during development
• Blastomeres become tightly packed and joined by intercellular junctions
• Highly selective recognition, enabling cells of similar type to stick together

Question 10

guides the organization of developing tissues sorting out according to their origins

Answer 10

cadherin-dependent cell-cell adhesion

Question 11

cadherin binds preferentially to

Answer 11

similar type of cell

Question 12

function of integrins

Answer 12

• Strengthen the binding of the blood cells to the endometrium
• Heterophilic binding to specific proteins
• Principal cell-surface receptors used by animal cells to bind to the extracellular matrix (ECM)
• transmembrane linkers between the ECM and cytoskeleton

Question 13

α5β1

Answer 13

ligand: fibronection

distribution: ubiquitous

phenotype when α subunit is mutated: death of embryo; defects in blood vessels, somites, neural crest

phenotype when β subunit is mutated: early death of embryo (at implantation)

Question 14

αβ16

Answer 14

ligand: fibronlamininection

distribution: ubiquitous

phenotype when α subunit is mutated: severe skin blistering; defects in other epithelia also

phenotype when β subunit is mutated: early death of embryo (at implantation)

Question 15

αllbβ3

Answer 15

ligand: fibrinogen

distribution: platelets

phenotype when α subunit is mutated: bleeding; no platelets aggregation (Glanzmann disease)

phenotype when β subunit is mutated: bleeding; no platelets aggregation (Glanzmann disease); mild osteopetrosis

Question 16

α6β4

Answer 16

ligand: laminin

distribution: hemidesmosomes in epithelia

phenotype when α subunit is mutated: severe skin blistering; defects in other epithelia also

phenotype when β subunit is mutated: severe skin blistering; defects in other epithelia also

Question 17

function of selectins

Answer 17

• Carbohydrate-binding proteins (lectins) on the cell surface
• Mediate transient cell-cell adhesions in the bloodstream
• Bind heterophilically to specific oligosaccharides on glycoproteins/glycolipids
• Control WBC binding to endothelial cells, enabling extravasation (WBC migration out of the bloodstream)

Question 18

Role of Selectins in WBC Extravasation

Answer 18

Selectins mediate initial weak adhesion (rolling) of WBCs on endothelial cells.

Question 19

Role of Integrins in WBC Extravasation

Answer 19

Integrins mediate strong adhesion and emigration to allow WBCs to stop and migrate out of the bloodstream into tissues.

Question 20

Immunoglobulin (Ig) Superfamily of Proteins

Answer 20

Ca²⁺-independent cell-cell adhesion

Contain one or more Ig-like domains that are characteristic of antibody molecules

Question 21

Members of Ig superfamily

Answer 21

1. neural cell adhesion molecule (NCAM)
2. nectin
3. ICAMs (intercellular cell adhesion molecules)

Question 22

Neural cell adhesion molecule (NCAM)

Answer 22

nerve cells

Question 23

Nectin

Answer 23

collaborates with cadherin to help build and strengthen adherens junctions in many tissue

Question 24

ICAMs (intracellular adhesion molecules)

Answer 24

Bind to integrins on blood cells when blood cells migrate out of the bloodstream

Question 25

adherens junction

Answer 25

classical cadherins classical cadherin on neighboring cell actin filaments α-catenin, β-catenin, p120-catenin, vinculin

Question 26

desmosome

Answer 26

nonclassical cadherins (desmoglein, desmocollin) desmoglein and desmocollin on neighboring cell intermediate filaments plakoglobin, plakophilin, demoplakin

Question 27

actin-linked cell matrix junction

Answer 27

integrin extracellular matrix proteins actin filaments talin, kindlin, vinculin, paxillin, focal adhesion kinase (FAK), numerous others

Question 28

hemidesmosome

Answer 28

α6β4 integrin, type XVII collagen extracellular matrix proteins intermediate filaments plectin, BP230

Question 29

type of cell junctions

Answer 29

1. tight junction 2. anchoring junctions a. adhering junction b. desmosome c. hemidesmosome 3. gap junction

Question 30

role of Tight junctions

Answer 30

Block the passageways through the gaps between epithelial cells, preventing extracellular molecules from leaking from one side to the other

Question 31

role of tight Junctions (Vertebrates)

Answer 31

Impermeable to macromolecules, but permeability to small molecules varies by epithelium Example: Small intestine is ~10,000× more permeable to inorganic salts than the urinary bladder Maintenance of vectorial transport function of cells

Question 32

role of Anchoring junctions

Answer 32

Mechanical attach cells (and their cytoskeletons) to their neighbors or to the extracellular matrix Abundant in tissues that are subjected to severe mechanical stress Heart, muscle and epidermis

Question 33

seals gap between epithelial cells

Answer 33

tight junction

Question 34

connects actin filament bundle in one cell with that in the next cell takes in a form of adhesion belt

Answer 34

adherens junctions

Question 35

desmosome

Answer 35

connects intermediate filaments in one cell to those in the next cell are buttonlike points rivet (fasten) cells together, connect intermediate filaments of adjoining cells to distribute tensile or shearing forces mechanical strength

Question 36

gap junction

Answer 36

allows the passage of small water-soluble molecules from cell to cell allow cell to cell communication mediate the passage of chemical or electrical signals from one interacting cell to its partner

Question 37

anchors actin filaments in cell to extracellular matrix

Answer 37

actin-linked cell-matrix junction

Question 38

hemidesmosome

Answer 38

heanchors intermediate filaments in cell to extracellular matrix Or half-desmosomes, resemble desmosomes morphologically and in connecting intermediate filaments Connect the basal surface of the epithelial cell to the underlying basal lamina

Question 39

anchoring junctions three types

Answer 39

* Adherens junctions * Desmosomes * Hemidesmosomes

Question 40

Severe blistering of the skin, with leakage of body fluids into the loosened epithelium Due to antibodies against one of desmosomal cadherin proteins desmogleins 1 and 3. disrupted desmosomes; intact hemidesmosomes

Answer 40

Pemphigus vulgaris

Question 41

Transmembrane linker proteins

Answer 41

integrins

Question 42

Autoimmune disease directed against hemidesmosome antigens intact desmosome, disrupted hemidesmosomes

Answer 42

Bullous pemphigoid

Question 43

Cell-matrix junctions Actin filament attachment sites

Answer 43

Focal adhesions

Question 44

is spanned by channel forming proteins (connexons) Allow cells to share inorganic ions and small molecules Enable chemical and electrical coupling between connected cells

Answer 44

gap junctions

Question 45

Functional significance of Gap junctions

Answer 45

* Coordinates activities of electrically active cells * Allow action potentials to spread rapidly from cell to cell, without delay that occurs at chemical synapses * Synchronizes contractions heart and smooth muscle cell

Question 46

* Only intercellular junctions in plants * Function like gap junctions

Answer 46

Plasmodesmata

Question 47

Anchoring junctions: Actin filament attachment sites

Answer 47

1. cell-cell junctions (adherens junctions) 2. cell-matrix junctions (actin-linked cell-matrix adhesions)

Question 48

Anchoring junctions: Intermediate filament attachment sites

Answer 48

1. cell-cell junctions (desmosomes) 2. cell-matrix junctions (hemidesmosomes)

Question 49

Occluding junctions

Answer 49

OCCLUDING JUNCTIONS 1. tight junctions (in vertebrates) 2. septate junctions (in vertebrates)

Question 50

Channel-foriming junctions

Answer 50

1. gap junctions (in animals) 2. plasmodesmata (in plants)

Question 51

Signal-relaying junctions

Answer 51

1. chemical synapses (in the nervous system) 2. immunological synapses (in the immune system) 3. transmembrane ligand-receptor cell-cell signaling contacts (Delta-Notch, ephrin-Eph, etc.). Anchoring, occluding, and channel-forming junctions can all have signaling functions in addition to their structural roles