Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

TRANSPORT FROM THE ER THROUGH THE GOLGI APPARATUS
715
cis
Golgi
network
(CGN)
cis cisterna
medial cisterna
trans cisterna
trans
Golgi
network
(TGN)
(A)
secretory vesicle
cis FACE
trans FACE
Golgi vesicle
Figure 13–26 The Golgi apparatus.
(A) Three-dimensional reconstruction
from electron micrographs of the Golgi
apparatus in a secretory animal cell. The
cis face of the Golgi stack is that closest
to the ER. (B) A thin-section electron
micrograph of an animal cell. In plant
cells, the Golgi apparatus is generally
more distinct and more clearly separated
from other intracellular membranes than
in animal cells. (A, redrawn from
A. Rambourg and Y. Clermont, Eur. J. Cell
Biol. 51:189–200, 1990. With permission
from Wissenschaftliche Verlagsgesellschaft;
B, courtesy of Brij J. Gupta.)
nuclear
envelope
rough ER
vesicular
tubular
clusters
(B)
1 µm
The Golgi Apparatus Consists of an Ordered Series of
Compartments
Because it could be selectively visualized by silver stains, the Golgi apparatus was
one of the first organelles described
MBoC6
by
m13.25/13.25
early light microscopists. It consists of a
collection of flattened, membrane-enclosed compartments called cisternae, that
somewhat resemble a stack of pita breads. Each Golgi stack typically consists of
four to six cisternae (Figure 13–26), although some unicellular flagellates can have
more than 20. In animal cells, tubular connections between corresponding cisternae
link many stacks, thus forming a single complex, which is usually located near
the cell nucleus and close to the centrosome (Figure 13–27A). This localization
depends on microtubules. If microtubules are experimentally depolymerized, the
Golgi apparatus reorganizes into individual stacks that are found throughout the
cytoplasm, adjacent to ER exit sites. Some cells, including most plant cells, have
hundreds of individual Golgi stacks dispersed throughout the cytoplasm where
they are typically found adjacent to ER exit sites (Figure 13–27B).
(A)
(B)
Figure 13–27 Localization of the Golgi
apparatus in animal and plant cells.
(A) The Golgi apparatus in a cultured
fibroblast stained with a fluorescent
antibody that recognizes a Golgi resident
protein (bright orange). The Golgi apparatus
is polarized, facing the direction in which
the cell was crawling before fixation.
(B) The Golgi apparatus in a plant cell that
is expressing a fusion protein consisting
of a resident Golgi enzyme fused to green
fluorescent protein. (A, courtesy of John
Henley and Mark McNiven; B, courtesy of
Chris Hawes.)