3. GOLGI COMPLEX
A membranous complex of
vesicles, vacuoles, and
flattened sacs in the cytoplasm
of most cells involved in
intracellular secretion and
transport.
Found in most eukaryotic
cells.
Golgi Complex sometime
also called as the Golgi Body
or Golgi Apparatus
4. DISCOVERY
Golgi apparatus is named after the
scientist who discovered it.
Camillo Golgi was an Italian biologist
who discovered this organelle with a light
microscope in 1898.
He developed a method that stained it
intensely and made possible the
demonstration of its occurrence in a wide
variety of cell types.
This method is known as Golgi Staining
or Golgi Impregnation.
5. MORPHOLOGY
The Golgi is composed of stacks
of membrane-bound structures
known as Cisternae.
A cisterna (plural cisternae)
comprises a flattened membrane
disk that makes up the Golgi
apparatus.
Usually a Golgi has 6-7 cisternae.
Each Golgi stack has a distinct
orientation.
A complex network of tubules
and vesicles is located at the
edges of these cisternae.
6. MORPHOLOGY
• The cisternae stack has Two faces :
Cis-Golgi
Trans-Golgi
7. CIS-GOLGI
The side faces the Endoplasmic reticulum is Cis Face and is the entry face
that receives small membrane vesicles from the ER.
Vesicles from the endoplasmic reticulum fuse with the cis-Golgi network and
subsequently progress through the stack to the trans-Golgi network.
The cis is the site at which transport vesicles bringing newly synthesized
products from the endoplasmic reticulum with and add their contents to the
Golgi cisternae.
A complex network of anatomizing (connecting) membrane tubules attach to
and cover cisternae on the cis face and serve as a docking site for transport
vesicles.
Each region contains different enzymes which selectively modify the contents
depending on where they are destined to reside.
8. TRANS-GOLGI
The side faces the cell membrane is Trans Face and is the exit face where vesicles
leave the Golgi and move to their targets, including the exterior of the cell.
As the last station of the Golgi complex, the trans-Golgi network (TGN) plays a
pivotal role in directing proteins in the secretary pathway to the appropriate cellular
destination.
Proteins synthesized on membrane-bound ribosomes are transported through the
Golgi apparatus and, on reaching the trans-Golgi network, are sorted for delivery to
various cellular destinations.
Sorting involves the assembly of cytosol-oriented coat structures which preferentially
package cargo into vesicular transport intermediates.
Protein sorting into different transport vesicles requires specific interactions between
sorting motifs on the cargo molecules and vesicle coat components that recognize
these motifs.
9. FUNCTIONS
The Golgi apparatus is integral in modifying, sorting, and packaging
macromolecules for cell secretion (exocytosis) or use within the cell.
It primarily modifies proteins delivered from the rough endoplasmic
reticulum, then sends the modified macro-molecules to different parts
of the cell or outside of the cell.
It is also involved in the transport of lipids around the cell, and the
creation of lysosomes.
In this respect it can be thought of as similar
to a post office; it packages and labels items
which it then sends to different parts of the cell.
10. FUNCTIONS
The Golgi plays an important role in the synthesis of proteoglycans,
which are molecules present in the extracellular matrix of animals.
It is also a major site of carbohydrate synthesis.
A newly characterized protein, GAAP (Golgi anti-apoptotic protein),
almost exclusively resides in the Golgi and protects against cell
destruction known as apoptosis by an as-yet undefined mechanism.
Sometimes vital proteins needed in the rough endoplasmic reticulum
are transported along with the other proteins in the Golgi complex.
The Golgi complex has a mechanism for trapping them and sending
them back to the rough endoplasmic reticulum.
11. WORKING OF GOLGI COMPLEX
Proteins are translated and modified
with in the rough endoplasmic reticulum.
In order to complete their
modifications, they are transported in
membrane-bounded vesicles to the cis
side of the Golgi apparatus.
Transport vesicles from the rough ER
fuse together and become the cis
cisterna of the Golgi.
12. WORKING OF GOLGI COMPLEX
Once they reach the Golgi apparatus,
additional modifications are made to
the transported proteins by resident
Golgi enzymes. These modifications
are key in ensuring the proteins reach
their final destinations once they leave
the Golgi apparatus.
The Golgi apparatus is divided into
distinct regions. These include the cis
cisterna, nearest the ER, the centrally
located medial cisternae, the trans
cisterna, and the trans Golgi Network
(TGN).
13. WORKING OF GOLGI COMPLEX
According to the cis maturation
model, the proteins are transported
through the Golgi stack as the cisterna
containing them migrate, or mature, in
a cis-to-trans direction. New vesicles
from the ER continually supply new cis
cisterna as trans Golgi network
vesicles mature.
Within the trans Golgi
network, proteins are sorted by their
final destinations. This is
accomplished by receptor molecules
embeddedin the membrane of the
TGN.
14. WORKING OF GOLGI COMPLEX
When proteins have reached their
correct location within the TGN, the
membrane at those locations buds off
into vesicles. More than one protein can
be contained within each transport
vesicle.
Once released, the vesicles carry their
cargo proteins to a final location.
Possible destinations include the
lysosome, the digestive organelle of the
cell, and the plasma membrane, where
the proteins can be released elsewhere
in the organism.
15. TRANSPORTATION
The flow of cargo proteins through Golgi apparatus is from cis to
trans.
Despite this flow there are many resident proteins that are localized
in particular parts of the Golgi.
How newly produced proteins travel from the ER to the Golgi
complex and travel among Golgi stacks while the resident proteins
stay in place ?
Vesicle Transport Model
Cisternal Maturation Method
16. TRANSPORTATION
• Cisternal Maturation Method
• Created by Jennifer Lippincott Schwartz from the National Institute of Child health and human
development.
• The cis-most cisterna is the youngest, having been recently formed from incoming vesicles
• The trans-most cisterna is the oldest and breaks up into vesicles as material is moved to the trans
Golgi network
• Cargo proteins are carried with the cisterna; resident proteins are returned to their proper location
by retrograde movement of vesicles.
17. TRANSPORTATION
Vesicle Transport Model
• This Model was created by Gram Warren of Yale School of medicine
• One model suggests that proteins are transported enclosed in vesicles. Another model
proposes that one stack of the Golgi "matures" into the next stack.
• Cargo proteins (but not resident proteins) are moved from stack to stack by vesicle
transport.
• This sorting also involves both forward, anterograde (cis to trans), and backward, or
retrograde (trans to cis), flow of vesicles with proteins, moving back up the stack.
• Resident proteins that are carried to locations trans to their normal location are transported
back by retrograde movement of vesicles
