2. 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…
3. Plants versus Animals
Major types of intercellular junctions in animals:
Tight Junctions
Gap Junctions
Desmosomes
Adherens Junctions
Plants have plasmodesmata
4. Tight Junctions
Multiple strands of protein
form the tight junction
More strands = more
impermeability
Each strand formed from
proteins
Claudins
Occludins
5. 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…
6. 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
7. 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…?
8. 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
9. Desmosomes
Also called “Anchoring
Junctions”
Arranged randomly on the
lateral side of cells
membranes
The adhesion protein
bridges the space between
the cells
10. 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
11. Adherens Junctions
They are composed of…
Cadherins
bind to the catenins
that are connected to
the actin filaments
12. 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
14. 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
15. 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
16. Structure of Plasmodesmata
Has continuous plasma
membrane
Desmotubule: gives stability
Cytoplasmic sleeve: fluid
filled space
allows certain molecules
to pass through
17. 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
