Intercellular Connections Flashcards
Intercellular Connections
Neighboring cells often adhere, interact, and communicate via sites of direct physical contact
Intercellular Connections in ANIMALS
1) Gap Junctions
2) Tunneling Nanotubules (TNTs)
3) Desmosomes
4) Tight Junctions
Intercellular Connections in PLANTS
Plasmodesmata
Gap Junctions
Connects the outside of two cells AND their cytoplasm
–>Physically tethers the cells together
(A cytoplasmic channel between two cells)
Gap Junctions Composition
Made up of 2 connexons (one from each interacting cell)
–> Cytoplasmic channel = hydrophilic
–> Outside of junction = hydrophobic
Connexon
Made up of 6 connexin proteins (alpha helix proteins)
Gap junctions “open” when ________
2 connexons interact
(junction is “closed” when there is only one connexon)
Do things pass through gap junctions?
YES –> Mainly polar or charged molecules as the channel is hydrophilic
Tight Junctions
Areas where membranes of adjacent cells are FUSED
–> Creates ONE single SHARED membrane in the region of the junction
–> Tethers cells together
Do things pass through tight junctions?
NO: Tight junctions are IMPERMEABLE
–> They form a continuous seal around the cells
Tight junctions prevent…
leakage of any cell content through the membranes
(establishes a barrier to prevent anything from moving across a layer of cells)
Tight junctions are like…
Button snaps on a jacket
Tight junctions between cells in the bladder…
prevent the leakage of urine out of the bladder –> Keeps it contained through the watertight seal created between the epithelial cells
Tight junctions are similar to but STRONGER than…
desmosomes
Desmosomes
Anchor adjacent cells together
–> Impermeable junctions
–> Fastens cells together in “strong sheets”
Desmosome composition
Cells are anchored together through LINKER PROTEINS on the cell surfaces
Intermediate Filaments anchor the desmosomes in the cytoplasm
Desmosomes serve what purpose in muscle cells?
Attach muscle cells to produce muscle tissue
Tunneling Nanotubules
TNTs: Actin driven protrusion that extends from one cells to a target cell which then fuses with the target cell’s membrane
–> Creates cytoplasmic bridge: allows for passage of materials between cells
TNT Cytoplasmic Bridge Composition
1) Contains a shared cytoplasmic region
2) Contains a filamentous actin (F-actin) running through the middle of it
–> Allows molecules to move through the nanotubule using motor proteins
Plasmodesmata
Channels that connect plant cells together
–> Cytoplasmic connections (channels) THROUGH cell walls
Layers of Plant Cell Wall System
Outer to inner:
1) Primary cell wall (wall cell was “born” with)
2) Secondary cell wall (Inner wall)
3) Cell membrane
4) Cytosol
Primary Cell Wall
The outer layer of the cell wall
–> Plant was “born with it”
Secondary Cell Wall
The inner layer of the cell wall
–> Created “after birth” of cell
Middle Lamella
Space between plant cells
Plasmodesmata unifies…
most of the plant into one living continuum
–> The cytoplasm is continuous between cells connected with plasmodesmata
–> The ER is also continuous
Plasmodesmata also contains…
The ER
–> ER from one cell connects to the ER from another cell through the plasmodesmata
–> Creates one continuous ER system
2 states of plasmodesmata are:
Normal State = Smaller molecular transport (“more closed”)
Enlarged State = Larger molecular transport (“more open”)
