INTERCELLULAR

JUNCTIONS

Priya Mehta

Intercellular

what!?!

The Function

Cell junctions allow activities of individual cells that

make up the systems to be co-ordinated

Enables each system to function as an integrated whole

They are fundamental to the interactions between

cells.

Ohh okay…

Plants versus Animals

Major types of intercellular junctions in animals:

Tight Junctions

Gap Junctions

Desmosomes

Adherens Junctions

Plants have plasmodesmata

Tight Junctions

Multiple strands of protein

form the tight junction

More strands = more

impermeability

Each strand formed from

proteins

Claudins

Occludins

The Function of Tight Junctions

At tight junctions

Plasma membranes of neighboring cells are tightly pressed against each other

Form continuous seals around the cells Prevents…

leakage of extracellular fluid across a layer of epithelial cells

passage of molecules and ions through the space between cells.

Ex: Make us watertight Or else you might look

like him…

Gap Junctions

Also called “Communicating

Junctions”

2 opposing connexons join across intercellular space.

Connexons: assembly of six proteins that create gap between two plasma membranes

The Function of Gap Junctions

The created gap…

provides cytoplasmic channels from one cell to an adjacent

cell

allows for communication through exchange of materials and transmission of electrical impulses

Necessary for communication between cells in…?

Properties of Gap Junctions

Ions/molecules are able to pass through

Some molecules too big

Isolate damaged cells so damage does not spread

Damaged gap junction =

bad

Desmosomes

Also called “Anchoring

Junctions”

Arranged randomly on the

lateral side of cells

membranes

The adhesion protein

bridges the space between

the cells

The Function of Desmosomes

Fasten cells together

into strong sheets

Attach muscle cells to

each other in a muscle

Muscle tears can involve

rupture of desmosomes

Adherens Junctions

They are composed of…

Cadherins

bind to the catenins

that are connected to

the actin filaments

The Function of Adherens Junction

Provide strong mechanical attachments between

adjacent cells

They serve as a bridge connecting the actin

cytoskeleton of neighboring cells through direct

interaction

Summary of Junctions in Animals

Plasmodesmata (In Plants)

Narrow channels between

cell walls of neighboring

plant cells

Enables…

the transport of proteins, ions, and water

communication

transfer of chemical signals

Creation of Plasmodesmata

Part of the smooth ER gets trapped during cytokinesis

small pits created where PD form

PD found in primary pit fields, or small regions in cell walls

Structure of Plasmodesmata

Has continuous plasma

membrane

Desmotubule: gives stability

Cytoplasmic sleeve: fluid

filled space

allows certain molecules

to pass through

How function is affected

PD can close when there is

a significant pressure

differential between

adjacent cells

Changes in levels of

calcium, pH, and light

impact function

Sources

http://micro.magnet.fsu.edu/cells/plants/images/plasmodesmatafigure1.jpg

http://3dbiology.pbworks.com/f/1281622049/plasmodesmata.jpg

http://academic.kellogg.edu/herbrandsonc/bio201_mckinley/f4-1b_polarity_and_inte_c.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/6/6d/Cellular_tight_junction_en.svg/250px-Cellular_tight_junction_en.svg.png

http://academic.brooklyn.cuny.edu/biology/bio4fv/page/gap%20junctions1000a.JPG

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellJunctions.gif

http://upload.wikimedia.org/wikipedia/commons/8/86/Desmosome.gif

That wasn’t

so bad!