Cell adhesions, cell junctions and extracellular structures

Question 1

Epithelium

Answer 1

sheets of cells that are
polarized, with discrete functional
domains at opposite ends (apical and
basal) of the cells.

Question 2

Connective tissue

Answer 2

more loosely
organized, in which cells are attached
to each other, a rigid scaffold, or both

Question 3

Cell-Cell Junctions

Answer 3

Specialized structures where
two cells come together are
called cell-cell junctions

Question 4

Type of animal cell junctions

Answer 4

• Adhesive junctions
• Tight junctions
• Gap junctions

Question 5

plant junctions

Answer 5

Plant cells have special structures
called plasmodesmata

Question 6

cell table

Answer 6

Question 7

Adhesive Junction

Answer 7

Link adjoining cells
* Adhesion proteins are key
* Some need a linker protein
* Cadherins
* Are dynamic

Question 8

Types of adhesive junctions interactions

Answer 8

Homophilic interactions: same
* Heterophilic interactions: different

Question 9

Cadherin characterisation

Answer 9

“Repeats” in their extracellular domain
➢ A transmembrane domain.
➢ Varying cytosolic ends.

Question 10

E-cadherins

Answer 10

E-cadherins are found on epithelial cells

Question 11

P-cadherins

Answer 11

P-cadherins in placenta (and other tissues)

Question 12

Cadherin function

Answer 12

• The amount and type of cadherins on cell surfaces help
  segregate cells into specific tissues.
• Cadherin expression is essential for organization of cells during
  development

Question 13

Desmosomes

Answer 13

Provide a tissue with structural
integrity
* The desmosomal cadherins are
called desmocollins and
desmogleins.
* Linker protein = planktoglobin

Question 14

cell-cell adhesions for cellular events

Answer 14

• Lectins
• Cell adhesion molecules
  (CAMs)
• Selectins – e.g. Leukocyte
  adhesion during
  inflammation.
  insert

Question 15

Tight Junctions

Answer 15

Seal the gap between
adjacent epithelial
cells

Question 16

Tight junction protein types

Answer 16

Proteins include:
➢occludin
➢junctional
adhesion
molecules (JAMs)
➢claudins

Question 17

Gap Junctions

Answer 17

• Allow direct electrical & chemical communication
• Connexons form 3 nm wide channels

Question 18

ECM types

Answer 18

bone
Cartlidge
Connective tissue

Question 19

Bone

Answer 19

Rigid ECM with few
interspersed cells

Question 20

Cartlidge

Answer 20

More flexible than bone

Question 21

Connective tissue

Answer 21

Gelatinous with
interspersed fibroblasts

Question 22

Three Classes of ECM Molecules

Answer 22

1. Structural proteins → collagens & elastins
2. Protein-polysaccharide complexes → proteoglycans
3. Adhesive glycoproteins →fibronectins & lamins

Question 23

collagen

Answer 23

Question 24

Elastin

Question 25

Proteoglycans

Answer 25

glycoproteins where many glycosaminoglycans (GAGs) attach to a single protein

Question 26

Adhesive Glycoproteins

Answer 26

Adhesive Glycoproteins Anchor Cells to the Extracellular Matrix * Direct links between the ECM and the plasma membrane are reinforced by a family of adhesive glycoproteins * They have multiple domains to bind molecules in the ECM and receptors on membranes * Laminins and fibronectins

Question 27

Fibronectins

Answer 27

* Glycoproteins in the ECM * Many isoforms exist * 2 subunits connected by SS bonds * Rod-like domains bind specific ECM molecules / cell surface receptors

Question 28

Laminins

Answer 28

Glycoprotein * Bind cells to the basal lamina

Question 29

Basil lamina

Answer 29

* Basil lamina = structural support & barrier * Cells can alter properties of the basil lamina * Matrix metalloproteinases degrade local ECM at the basil lamina

Question 30

Laminin structure

Answer 30

Question 31

Integrins

Answer 31

* Cell surface receptors → bind ECM constituents * Transmembrane proteins with α&β domain * Many isoforms: - α5β1 binds fibronectin - α6β1 binds laminin

Question 32

Hemidesmosomes

Answer 32

* In epithelial cells * α6β4 integrin * Attach to laminin in the basil lamina; to keratin in the cytoskeleton

Question 33

Anchorage-dependant growth

Question 34

Anchorage independent growth

Question 35

paracellular transport and barrier

Question 36

tight junction structure

Question 37

Leukocyte rolling

Answer 37

Lectins allow leukocytes to roll on top of epithelial cells instead of just free-floating by being passed from one cell to another -selectin expression is increased by inflation insert

Question 38

Focal adhesions

Answer 38