Golgi apparatus
The Golgi apparatus (also Golgi body or Golgi
Complex is an organelle found in most eukaryotic cells.
It was identified in 1898 by the Italian physician Camillo
Golgi and was named after him. The primary function of
the Golgi apparatus is to process and package
macromolecules, such as proteins and lipids, after their
synthesis. It is particularly important in the processing of
proteins for secretion. The Golgi apparatus forms a part
of the cellular endomembrane system. The Golgi is
composed of stacks of membrane-bound structures
known as cisternae.

• The Golgi is composed of stacks of membrane-
bound structures known as cisternae A
mammalian cell typically contains 40 to 100
stacks. Between four and eight cisternae are
usually present in a stack. An individual stack is
sometimes called a dictyosome . About four to
eight cisternae are usually present in a stack
Each cisterna comprises a flattened membrane
disk, and carries Golgi enzymes to help or to
modify cargo proteins that travel through them.

• The cisternae stack has four functional regions: the
cis-Golgi network, medial-Golgi, endo-Golgi, and
trans-Golgi network . Vesicles from the endoplasmic
reticulum fuse with the network and subsequently
progress through the stack to the trans Golgi network,
where they are packaged and sent to the required
place. The three basic component of golgi apparatus
is Cisternae, Tubules, Vesicles. The tubules are array
of associated vesicles and anastomosing tubules(30-
50nm)surround the dictyosome and radiate from it
.The vesicle are of three types a) transitional
vesicles,b) secretory vesicles c) Clathrin vesicles.

• Small vesicles: ( transport vesicles)
formed from the GER membrane by budding
• newly synthesized protein from GER are
transported to the Golgi complex with the
transport vesicles
• about 300-800 A
in dimeter

• Cisternae: (flattened sacs or
saccules)
• The Golgi complex consist of
several membrane-bounded
stacked, flattened sacs (or
cisternae)
• The saccules are disk-like and
often slightly curved
(convex and concave
surfaces )

Function
• Cells synthesize a large number of different
macromolecules. The Golgi apparatus is integral in
modifying, sorting, and packaging these
macromolecules for cell secretion (exocytosis) or use
within the cell. It primarily modifies proteins delivered
from the rough endoplasmic reticulum but is also
involved in the transport of lipids around the cell, and
the creation of lysosomes. Enzymes within the
cisternae are able to modify substances by the
addition of carbohydrates (glycosylation) and
phosphates (phosphorylation).

• the Golgi imports substances such as nucleotide
sugars from the cytosol. 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 .This includes the
productions of glycosaminoglycans long
unbranched polysaccharides which the Golgi
then attaches to a protein synthesised in the
endoplasmic reticulum to form proteoglycans .

• The Golgi complex controls
trafficking of different types
of proteins.
• Some are destined for
secretion.
• Others are destined for the
extracellular matrix.
• Other proteins, such as
lysosomal enzymes, may need
to be sorted and sequestered
from the remaining constituents
because of their potential
destructive effects