Extracellular Matrix and Cell-Cell Interactions

Question 1

What is the function of the extracellular matrix?

Answer 1

Fills the spaces between cells and binds cells and tissues together

Question 2

What are epithelial tissues?

Answer 2

thin, sheet-like extracellular matrix (basal lamina) that underlies epithelial cells and binds them to underlying connective tissues

Question 3

What are muscle, adipose, and nerve tissues surrounded by?

Answer 3

A thin basal lamina

Question 4

What are some examples of connective tissues?

Answer 4

bone, tendon, cartilage, and loose connective tissue underlying skin

Question 5

What are extracellular matrices composed of?

Answer 5

Tough fibrous structural proteins embedded in a gel-like polysaccharide material known as ground substance

Question 6

What do specialized adhesion molecules do?

Answer 6

anchor cells to the extracellular matrix

Question 7

What is collagen? How many types of collagen are there?

Answer 7

Collagen is the major structural protein of the extracellular matrix, of which the family contains at least 27 different members.

Question 8

What is the repeating amino acid primary sequence of collagens?

Answer 8

A triple repeat of Gly-X-Y, where X is usually proline and Y is usually hydroxyproline (could also be hydroxylysine)

Question 9

What do the repeat structures of collagens form?

Answer 9

Form triple helices with three polypeptide chains wound around each other

Question 10

How are collagen fibrils formed? Where does this assembly take place?

Answer 10

triple helices line up in staggered arrangement and are cross-linked together.
takes place within the ECM following the secretion of procollagen from the cell via the ER/Golgi pathway.

Question 11

What is the structure of network-forming collagens?

Answer 11

network-forming collagens have numerous interruptions of helical regions that are cross-linked together (more flexible)

Question 12

What is elastin?

Answer 12

The principle protein of elastic fibres, cross-linked into a network by covalent bonds

Question 13

What are glycosaminoglycans (GAGs)?

Answer 13

Gel forming polysaccharides of the extracellular matrix that consist of repeating units of disaccharides

Question 14

How do GAGs create a hydrated gel-like structure?

Answer 14

negative charges bind positively charged ions, attracting and trapping water molecules

Question 15

How do GAGs form proteoglycans?

Answer 15

Covalently link to specific proteins to form proteoglycans

Question 16

How are larger proteoglycan aggregates formed?

Answer 16

A number of proteoglycans interact with hyaluronan chains (GAGs) to form large complexes in the ECM

Question 17

What are matrix adhesion proteins responsible for?

Answer 17

Linking the components of the matrix to one another and to the surface of cells.

Question 18

What is fibronectin?

Answer 18

The principal adhesion protein of connective tissues

Question 19

What is laminin?

Answer 19

The principal adhesion protein of the basal lamina

Question 20

What is nidogen?

Answer 20

A protein that links laminin to collagen type IV

Question 21

What are integrins?

Answer 21

the major cell surface proteins responsible for the attachment of cells to the extracellular matrix, and serve as anchors for the cytoskeleton within the cell.

Question 22

What do integrins consist of?

Answer 22

Dimers of one alpha and one beta subunit

Question 23

What is focal adhesion?

Answer 23

A type of cell-matrix junction that is linked to actin filaments and attaches a variety of cells to the extracellular matrix

Question 24

What are hemidesmosomes?

Answer 24

A type of cell-matrix junction linked to intermediate filaments that mediate epithelial cell attachments at which specific integrin interacts with laminin at the basal lamina

Question 25

What do adherens junctions involve? How do they work?

Answer 25

Involves a family of integral plasma membrane proteins in adjacent cells known as cadherins.
cadherins link to the actin cytoskeleton intracellularly via catenind, and extracellularly with each other.

Question 26

What do desmosomes involve? How do they work/

Answer 26

Involves a family of cadherins known as desmoglein and desmocollin.
These cadherins link to the intermediate filament cytoskeleton intracellularly and with each other extracellularly.

Question 27

What do tight junctions do? (4 things)

Answer 27

• form a barrier between fluid compartments
• ensure any molecules moving across the epithelial cell layer must move through the cell, not between cells
• separate apical and basal domains of the plasma membrane
• prevent lateral movement of integral membrane proteins between the domains of the cell

Question 28

What is a junction complex?

Answer 28

A region of cell-cell contact containing a tight junction, an adherens junction, and a desmosome.

Question 29

What are gap junctions important for/

Answer 29

Cell-cell communication and coordination of cellular activity

Question 30

What is the structure of a gap junction?

Answer 30

An open channel, called a connexon, through the plasma membrane that provide direct connections between the cytoplasm of adjacent cells

Question 31

What do gap junctions allow for? What do they provide?

Answer 31

Allow for open flow of ions and other small molecules.

Provide a mechanism to couple metabolic and electrical activity of adjacent cells.

Question 32

What is connexin?

Answer 32

A protein that forms gap junctions