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Golgi apparatus or golgi complex or simple Golgi is an organelle
found in most of the eukaryotic cells .
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It was one of the first organelle to be discovered and observed in
detail.
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It was first identified by an Italian physician Camillo Golgi in 1897 and
is named after him as GOLGI.
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The discovery was confirmed in 20th century with the invention of
electron microscope .
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The Golgi structure is a smooth, curvy structure.
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It is a flattened stack of membrane enclosed sacs or cisterns
with vacuoles and vesicles. It has a front end and a back
end.

Polarized Structure show that the front end is called the cis
face and the back end is called the trans face.

Golgi apparatus has cisternae are the flattened membrane
folds and secretory vesicles which are what the cell
discharges.
Number of stacks in each apparatus vary from 6 to 8.
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.
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Plays role in packaging and processing
of materials synthesized within cell,

a. lysosomal enzymes
b. secretory products
 Golgi are involved in the sorting and
post-translational modification of
proteins
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During the passage of proteins through the Golgi compartments, various covalent
modifications take place in order to provide the specific structure and function to the
protein

Modification of existing glycosyl groups, O-glycosylation, sulfation (addition of sulfates
to OH on tyrosine), and phosphorylation all take place within the various Golgi
compartments.
For simplicity, the primary focus of this lecture series will be the modification of
proteins by glycosylation
As mentioned previously, the ER N-glycosylates various proteins with oligosaccharides
The Golgi then modifies these oligos providing either a COMPLEX
OLIGOSACCHARIDE and HIGH MANNOSE CONTAINING
OLIGOSACCHARIDE.
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The high mannose oligo is produced by removing glucose and N-acetylglucosamine moeities while the
complex oligo is produced adding addition monosaccharides consecutively.
Some proteins require additional oligosaccharides to provide a specific function. The
Golgi also modifies proteins by O-glycosylation. Serines are used for this type of posttranslational modification.
SYNTHESIS
 SECRETION
 SULFATION
 APOPTOSIS
 PHOSPHORYLATION
 CELL SPECIFIC FUNCTIONS

VESICULAR TRANSPORT :
The basic function of the Golgi apparatus is the
transport of proteins within the cell. The Golgi
receives materials for transportation through the cis
face and sends the materials through to the trans
face once they are packaged and modified into
the vesicles. It functions in the collection,
packaging, and distribution of material. The
cisternae are the flattened membrane folds of the
Golgi apparatus that push together pinching off
secretory vesicles containing molecules which are
then discharged into the cell.
Golgi apparatus is involved in secretion
and synthesis of many different
molecules within the cell eg.
PROTEOGLYCANS, which are the
molecules present in extracellular matrix.
 It is also a major site for carbohydrate
synthesis eg. Glycosaminoglycans. The
enzymes in golgi link several of these
GAG’s.

Another important function of Golgi is
sulfation via sulphotransferases.

APOPTOSIS: a newly identified protien
called GAAP (GOLGI ANTI APOPTOTIC
PROTIEN)resides in Golgi and protect cell
from apoptosis.
• Acid hydrolases targeted to the lysosome by a mannose-6phosphate residue. This modification takes place in the cisGolgi network.
•
Prior to modification the N-glycosyl group is modified to
produce a high mannose-containing oligo. Phosphate
addition to the C6 position is catalyzed by Nacetylglucosamine phosphotransferase. This enzyme binds to
and recognizes a signal patch on the folded hydrolase. The
N-acetyl glucosamine is then removed to produce a
mannose-6-phosphate

Golgi apparatus is found to play an important role in Alzheimer’s
disease. Alzheimer’s disease is a brain disorder where brain cells are
being destroyed. This is what gives a person memory loss and this
disease can lead to death. As the death of neurons increases the
affected brain region begins to shrink. The cause of this disease is
because there is too little removal of a specific type of protein.
Therefore, the Golgi apparatus isn’t functioning as it is suppose to in
collecting, transporting, and distributing the protein molecules.