Cell Junctions

Question 1

What are tissues?

Answer 1

Cells that are closely associated and preform a common or related function

Question 2

Four types of tissue

Answer 2

Epithelia, connective, muscle, nervous

Question 3

What is the epithelium

Answer 3

Covering/lining tissue

Question 4

What does a Gap Junction do?

Answer 4

Mediates cell to cell communication by permitting DIRECT transfer of ions and small molecules by connecting the cytoplasm in adjacent cells

Question 5

What are Gap Junctions composed of?

Answer 5

Hexamers of integral proteins: connexins and chordates

Question 6

What type of cells do Gap Junctions connect

Answer 6

Excitable Cells (nerve and muscle)

Question 7

Where are Gap Junctions found?

Answer 7

Joining virtually all cells in solid tissues

Question 8

How do Gap Junction isoforms change permeability

Answer 8

Different combinations of connexins

Question 9

How are Gap Junctions regulated

Answer 9

Changes or signals (neurotransmitters)

Question 10

How do Tight Junctions hold cells together?

Answer 10

Form a leak-proof intercellular seal by fusing adjacent cell membranes

Question 11

What determines Tight Junction Permeability?

Answer 11

The tissue it’s found in

Question 12

What are major aspects of Tight Junctions?

Answer 12

Claudin
Occludin
Zona Occludents

Question 13

What is Claudin

Answer 13

A main transmembrane protein found within a tight junction that is selectively permeable

Question 14

Dysregulation of what TJ protien causes cancers and other pathologies? Why?

Answer 14

Claudins.
Impaired barrier function leads to exacerbation of inflammation.
Epidermal growth factors influx contributes to tumorigenesis

Question 15

How does a pathogenic breach affect claudins?

Answer 15

Creates an overactive inflammatory response and affects claudin expression (they’re sensitive)

Question 16

What are Anchoring Junctions?

Answer 16

Complexes that adhere cells to other cells or extracellular matrix
Provide strong membrane spanning structure

Question 17

Types of Anchoring Junctions

Answer 17

Adherens junction
Desmosomes
Hemidesmosomes
Focal adhesion

Question 18

Adherens Junctions are connected to cytoskeleton by

Answer 18

Actins

Question 19

How are desmosomes connected to the cytoskeleton?

Answer 19

Intermediate filaments

Question 20

How are Hemidesmosomes connected to cytoskeleton?

Answer 20

Intermediate filaments

Question 21

How are Focal Adhesions connected to cytoskeleton?

Answer 21

Actins

Question 22

How are tight junctions connected to cytoskeleton

Answer 22

Actin

Question 23

What are Plaque Protiens?

Answer 23

internal Attachment within cell junction

Question 24

What are Transmembrane proteins?

Answer 24

External Attachment

Question 25

What is prerequisite to TJ assembly? And where are they located in proximity to TJ.

Answer 25

Formation of Adherens Junctions below.

Question 26

What determines Cadherin structure? What are some isoforms?

Answer 26

Structure depends on Ca++ ions. E-cadherin: eipithelial cells N-cadherin: Nerve, muscle and lens. P-Cadherin: Placenta and Epidermis

Question 27

How do Mutations in E-cadehrins cause cancer?

Answer 27

Disrupts the function or production. Loss of function associated with gain of invasiveness and metastatic potential of cells

Question 28

Where do Desmosomes play a critical role in the body?

Answer 28

In tissues subjected to mechanical stress such as the myocardium, bladder and skin.

Question 29

What do Hemidesmosomes and Focal adhesion do?

Answer 29

Aid in the interaction of a cell-extracellular matrix

Question 30

What do cell junctions do?

Answer 30

Provide mechanical support Separate cells for protection and traffic regulation Communication b/w cells Cell Polarity