Intercellular Connections

Question 1

Intercellular Connections

Answer 1

Neighboring cells often adhere, interact, and communicate via sites of direct physical contact

Question 2

Intercellular Connections in ANIMALS

Answer 2

1) Gap Junctions
2) Tunneling Nanotubules (TNTs)
3) Desmosomes
4) Tight Junctions

Question 3

Intercellular Connections in PLANTS

Answer 3

Plasmodesmata

Question 4

Gap Junctions

Answer 4

Connects the outside of two cells AND their cytoplasm

–>Physically tethers the cells together

(A cytoplasmic channel between two cells)

Question 5

Gap Junctions Composition

Answer 5

Made up of 2 connexons (one from each interacting cell)

–> Cytoplasmic channel = hydrophilic
–> Outside of junction = hydrophobic

Question 6

Connexon

Answer 6

Made up of 6 connexin proteins (alpha helix proteins)

Question 7

Gap junctions “open” when ________

Answer 7

2 connexons interact

(junction is “closed” when there is only one connexon)

Question 8

Do things pass through gap junctions?

Answer 8

YES –> Mainly polar or charged molecules as the channel is hydrophilic

Question 9

Tight Junctions

Answer 9

Areas where membranes of adjacent cells are FUSED

–> Creates ONE single SHARED membrane in the region of the junction

–> Tethers cells together

Question 10

Do things pass through tight junctions?

Answer 10

NO: Tight junctions are IMPERMEABLE

–> They form a continuous seal around the cells

Question 11

Tight junctions prevent…

Answer 11

leakage of any cell content through the membranes

(establishes a barrier to prevent anything from moving across a layer of cells)

Question 12

Tight junctions are like…

Answer 12

Button snaps on a jacket

Question 13

Tight junctions between cells in the bladder…

Answer 13

prevent the leakage of urine out of the bladder –> Keeps it contained through the watertight seal created between the epithelial cells

Question 14

Tight junctions are similar to but STRONGER than…

Answer 14

desmosomes

Question 15

Desmosomes

Answer 15

Anchor adjacent cells together

–> Impermeable junctions

–> Fastens cells together in “strong sheets”

Question 16

Desmosome composition

Answer 16

Cells are anchored together through LINKER PROTEINS on the cell surfaces

Intermediate Filaments anchor the desmosomes in the cytoplasm

Question 17

Desmosomes serve what purpose in muscle cells?

Answer 17

Attach muscle cells to produce muscle tissue

Question 18

Tunneling Nanotubules

Answer 18

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

Question 19

TNT Cytoplasmic Bridge Composition

Answer 19

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

Question 20

Plasmodesmata

Answer 20

Channels that connect plant cells together

–> Cytoplasmic connections (channels) THROUGH cell walls

Question 21

Layers of Plant Cell Wall System

Answer 21

Outer to inner:
1) Primary cell wall (wall cell was “born” with)
2) Secondary cell wall (Inner wall)
3) Cell membrane
4) Cytosol

Question 22

Primary Cell Wall

Answer 22

The outer layer of the cell wall
–> Plant was “born with it”

Question 23

Secondary Cell Wall

Answer 23

The inner layer of the cell wall
–> Created “after birth” of cell

Question 24

Middle Lamella

Answer 24

Space between plant cells

Question 25

Plasmodesmata unifies…

Answer 25

most of the plant into one living continuum

–> The cytoplasm is continuous between cells connected with plasmodesmata

–> The ER is also continuous

Question 26

Plasmodesmata also contains…

Answer 26

The ER

–> ER from one cell connects to the ER from another cell through the plasmodesmata

–> Creates one continuous ER system

Question 27

2 states of plasmodesmata are:

Answer 27

Normal State = Smaller molecular transport (“more closed”)

Enlarged State = Larger molecular transport (“more open”)