A Tour of the Cell

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13

Plasmodesmata

Tight junctions

Desmosomes

Gap junctions

Slide 106

Plasmodesmata in Plant Cells

Plasmodesmata are channels that perforate plant cell walls

Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell

Slide 107

Fig. 6-31

Interior of cell

Interior of cell

0.5 µm

Plasmodesmata

Plasma membranes

Cell walls

Slide 108

Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells

At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Desmosomes (anchoring junctions) fasten cells together into strong sheets

Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells

Animation: Tight Junctions

Animation: Desmosomes

Animation: Gap Junctions

Slide 109

Fig. 6-32

Tight junction

0.5 µm

1 µm

Desmosome

Gap junction

Extracellular

matrix

0.1 µm

Plasma membranes

of adjacent cells

Space

between

cells

Gap

junctions

Desmosome

Intermediate

filaments

Tight junction

Tight junctions prevent

fluid from moving

across a layer of cells

Slide 110

Fig. 6-32a

Tight junctions prevent fluid from moving across a layer of cells

Tight junction

Intermediate filaments

Desmosome

Gap junctions

Extracellular matrix

Space between cells

Plasma membranes of adjacent cells

Slide 111

Fig. 6-32b

Tight junction

0.5 µm

Slide 112

Fig. 6-32c

Desmosome

1 µm

Slide 113

Fig. 6-32d

Gap junction

0.1 µm

Slide 114

The Cell: A Living Unit Greater Than the Sum of Its Parts

Cells rely on the integration of structures and organelles in order to function

For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane

Slide 115

Fig. 6-33

5 µm

Slide 116