Golgi complex a organ of cell and cell cycle

Golgi body is a cell organ due

1. 14" Golgi Complex

Golgi complex is a stack of membranous flattened sacs and vesicles concerned with
cell secretion. = = 3 a

qu was first described by Camillo Golgi (1898) in the nerve cells of barn owl.)

he Golgi complex has been Variously named as Golgi body, dictyosome, lipochondrion,
internal reticular apparatus, canalicular system and tropho-spongium by various workers]

= Nuclear pore
Nucleus

Cisfernae

9

7

A Trans face
if Golgi apparatus
‘Smooth endoplasmic r
Fig.14.1 : Golgi complex

Generally, the term dietyosome is used for the Golgi body of invertebrates and plants
4 EXA
The Golgi is located in the cytoplasm.

Itisacell membrane bound organelle,

2. a
‘Golgi complex is absent cc

and preridophytes and RBC
si Structure of Golgi com!

Golgi complex isa stack of membranous flattened 5465

cet, certain Jung, sperm

lex
E nd vesicles interconnected

me ; Golgi sacs

Cisregion À

Medial region

Trans region ¢
lo

Secretory vesicle leaving the trans region
Fig. 14.2: Golgi apparatus.

The size ofthe Golgi complex is variable. Its larger and well developed in active cells like
gland cells and nerve cells and poorly developed in muscle cells. As the cells become older. the
Golgi tends to decrease in size. tis 1-3mm in length and 0.Smm in thickness,

Endoplasmic reticulum

Trans Golgi
Network

Smooth and
en FR coated vesicles

Ri Fig.14.3, Golgi complex.

[The position of Goleiisreaivel fg,
nucleus. For example, in seretory enter
Secretory side facing outside Inthe color
throughout the cytoplasm)

There is a clear region around the Gol
and éÿen endoplasmic reticulum, Jj Sepa this no ibesome,

Te E complex isa dise-shaped sie 0 exclusion "> Mitochondria, chloroplast
vesicles, ture formed by a sti

for eal
cells, it
the invert

e: Itusually oc

i sed Sally occupies nearthe

ran etd around the mucosa cad
nates and plants, the Golgi is distributed

of cisternae and peripheral

3. chcistemaismade up ofa pair of membranes continuousat the ends. The two membranes
enclose a cavity of about 150A. The cavities of cisternae atthe maturing face are wider.)

Menbrane ETS
=
==

So. Vai 2?

Fig.14.4: Cisterna of Golgi pci

Ge adjacent cisternae are cemented together by a cementing substance called
Cintercisternal material,

In many cases, many anastamosing tubules are given off from the cisternae{ In certain
cases, the cistemae contain pores and they are said to be fenestrated Golgi.

{he cistemacare slighty curved. Hence, the cistemae have convex and concave surfaces.
[Ene Golgi complex has two sides, namely forming face and maturing fa
he convex surface is the forming face or cis face. This face is towards the mucleus or
endoplasmic reticulum. Here new lamellae are added from endoplasmic reticulum.)

(he concave surface is the maturing face or trans face. The trans face is towards the
plasma membrane. Here large secretory vesicles are budded off

ene Extrinsic

protein
Head ag

Bu Ann i

Inner lipid sil
Invinsic

cod o Mine GT
Ba

proteins Sugar
Fig. 14.6: Fluid mosaic structure of Golgi membrane

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4. are closely associate
en pout 08 name py constriction ofthe
(These are small CA Enr Top ciherby budding
vile of de
ends ofthe cistemae.) a
Highlights

Golgi comple ih secreion

od sacs conce
Gol compte a ac of tened sa 4
+ Itis the post office ofthe cell. rtment ofthe cel
¢ tis the Diseriburion and Shipping Department OT
+ Itis a modifying, sorting, packaging uni
tas sore y Colin 189,
+ Is named after the discoverer, Golgi dla
+ Itis also called dictyosome or Golgi apparatus or Golgi bod
+ Itis a membrane bound organelle.
* Iti located in the eytoplasm midway between the nucleus and crop
+ Most ofthe animal cells contain only one Golgi complex; but oocytes, nerve

liver cells and plant cells contain many Golgi bodies.
+ Itis absent from prokaryotes, certain fungi, sperm cells of Bryophytes and
Peridophytes and RBC
+ Golgi complex consists of 2 components namely cisternae and vesicles
+ Cisternae are flattened sacs arranged in the form of a stack
* There are 4 to 100 cisterna ina Golgi complex. They are ar anged one above
the other
$ Bis adiacent cistemae are cemented together by intrcisternal mate
Each sac has a membrane anda cavity inside, > Nr nos
+ The membrane has a fluid mosae she
The Golgi complex has apolar,
5 The Golgi complex has sides namely a cis-faee
2 Tre Side facing the nucleus is called cis fuego à trans-face
* The cis-fae is also called formin
* he cis face new cena mee US comes
10 endoplasmic reticulum, Hence theo ce slo cios coming from
5 ec the cise ae shoe “also called forming face.
is-face acts as a receiving de
The trans-face is located near the are
+ Itis concave Plasma membrang
+ Inthe trans-face the cist
mae are

Tus ints face ac sa shipping JOE is also call ee
he cistemae are short in cigs “Parme “maturing phase.

trans-face. ‘and they ert
Ate increasing in length towards the

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5. parts
v unetion as “postman” or “cargo”. a
+ Golgi complex modify, sort out, package and secrete the proteins
bythe endoplasmic reticulum, à
+ The products of ER are carried by vesicles to the cis-face of Golgi.
+ The vesicles fuse with the Golgi and release the contents into the Golgi.
+ The products are processed by the Golgi.
+ They add molecules or chop tiny pieces atthe end.

+ The first cisterna buds off a vesicle containing the processed product.

+ The vesicle fuses with the second cisterna and the process is repeated until
the product reaches the trans side.

+ When the products pass through the cisternae the products are glycosylated
or sulphated ot phosphorylated. This is the labelling done by Golgi
complex.

+ These processes dictate to where the products should travel. Hence Golgi
complex is called the “major sorting centre”.

+ The labelled products are sorted and packed in vesicles.

+ These vesicles are cargo and they act as postman.

+ They bud off and move towards the plasma membrane. They fuse with the
plasma membrane and the products are poured out by exocytosis.

+ Some vesicles form lysosomes.

Chemical Composition

(Golgi contains 60% proteins and 40% lipids.

"The Golgi membrane lipoprotein in nature. The lipids are mainly phospholipids (cephalin
and lecithin). Enzymes such as ADPase, ATPase, CTPase, thyamine pyrophosphatase, acid
phosphatase, UDP, N-acetyl glucosamine-transferase, etc. are present. Cain has reported
the presence of carotenoids in the Golgi of Limnaea.

à Origin of Golgi

according to Palade (1955), the Golgi apparatus originates from the endoplasmic
reticulum. This concept has supporting evidences.

‘Another hypothesis suggested by Me Alear provides an explanation forthe or
bodies from nuclear membrane,

Functions of Golgi Apparatus
Golgi complex performs the following functions in living cell:
„Formation of Acrosome

‘The acrosome of sperm is developed from G aratus during spermatogenesis

During spermiogenesis, a vacuole appears in the Golgi apparatus. Inside the vacuole a
dense granule called proacrosomal granule develops. The vacuole and proacrosomal granule
gradually enlarge. The entire apparatus moves towards the nucleus and gets attached to the tip
‘ofthe nucleus. The granule is now called acrosomal granule and the entire structure is called
‘acrosome. It spreads over the nucleus as a cap.

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of Golgi

parat

6. Acrosomal

A

crosome
33 Acros
93 Acrsomal td Ai

gran

D E

rosome from Golgi.
Fig. 14.7 : Formation of ac

moc, wall formation in plant cell. During cytokinesis, the Gog
Gol complex involvedin cell wall fm

nation of cell plate

mult inthe equatorial plane and help inthe format» des

“The tral pres ol apar epithe lo on of el val me
chan ofl alsin Co completan enana ken

ternucleiPhragmoplast

—A

Cellplate

Fig.148 : Formation of cell wa

2: Plasma Membrane Formation
Golgi complex involves in the form,
ny vesicles formed from Golgi com

gis el becomes incorporated nat re a
Te exeytosisand endocytosis mainain normal size of 58 ™ENts of plasma membrane
renewal ofthe membrane consttuens SEO Plasma mern Ten
pain he Golgi comple sm
membrane,
2 Biogenesis of Lysosomes
Golg complexis involved inthe fon
a DT These vesiles
ses,

phat Plasma membrang Dari
lex: ase vie paa meme’ The membrane

the carbo
Sale Components of the plasma

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7. Golgimembrane joins with
plasma membrane

Fig.14.9 : Plasma membrane formation.
igi complex in turn bud off small vesicles called primary

lysosomes. The primary lysosomes fase wtf pinosomes)>¢phagosamesfo form secondary
ipsosomes. = assume

The cisternae of Go

Endoplasmic 4
etc Secondary

lysosome
Primary lysosome é

Membrane Trafficking
Golgi complex caries outa trafficking function in the transport of biosynthetic products.
They are transported within the cells (intracellular transport) or to out
(intercellular transport.
The intracellular transport includes the delivery of products from endoplasmic reticulum
to Golgi complex or from the Golgi complex to lysosomes or plasma membrane.

le the cells

The intercellular transport includes secretion of synthetic products tothe outside by
exocytosis.
Thus membrane trafficking ofthe following types
{1 Transport from endoplasmic reticulum to Golgi
2, Transport from Cis Golgi to Trans Golgi

¢ 3 Transport from Golgi to Plasma membrane

| 4. Transport from Golgi 10 Iysosomes.

Ui. Transport from Endoplasmic reticulum to Golgi: Proteins synthesized on the
ribosomes From the ribosomes, the poten molecules are transfered tothe lamen of endoplasmic
reiulum. The endoplasmic reticulum buds of vesicles containing protein molecules. The buds
move towards the cis-face of Golgi. They are fused withthe cisternae of Golgi and become
incorporated withthe cis-face ofthe cisternae.

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8. EI

Endoplasmic reticulum
Fig. 14.11: Transport of vesicles from endoplasmic reticulum to Golgi complex

2. Transport from Cis Golgi to Trans Golgi: The proteins, received on the Cis-side of

Gos, are moved through the stack of cisternae to the trans side
During this transport, the biosynthetic product (protein) is processed, concentrated,
glycosplated and sulphated to produce the desired product.
3. Transport from Golgi to Plasma Membrane : Golgi produces secretory vesicles on
trans- face. These vesicle contain biosynthetic products. These products vary with cells. For
le, Golgi membrane of intestinal cells transports mucus o plasma membrane, of mammary
gland cells transports milk particles and Golgi of nerve cells transports neurotransmitter to the

Synaptic knob

Synaptic vesicle À_/ Neuro:
transmitter

Plasma

k E Boon

Cis face” >
; I D €

Trans ace

Fig.14.13: Transport of ves

sicles to the plasma membrane and
ards the pl
‘ocytosis,

These vesicles move tow across.

egies lasma membr
‘esicles are released out by ex brane and fuse with it. The

contents of the

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9. A Transport from Golgi to Lyosomes The ydrolase enzymes synthesized in the
‘endoplasmic reticulum and are transported to the Golgi, From the Golgi, vesicles containing
hydrolases are budded off, They move to the lysosomes and fuse with then.

-

|
Ge ( A e

©
ZA z
egal No 4 bd Se Fat

Lysosome

KT

Fig.14.14 : Secretion by Golgi complex.

6,Secretion
Secretion is the process of elaborating and releasing a specific produ
The mucous cells secrete mucous; the salivary gland cells secrete saliva; The sebac
cells secret othe sweat gland cells s
gland cells Secréte enzymes, endocrine gland cells secrete hormones; the plasma cells secrete
antibodies; Nerve cells secrete neurotransmitters, mammary gland cells secrete milk.
‘Secretion isdone by the Golgi complex. Golgi complex functions asa transporting channel
from the site of synthesis tothe outside
The product is synthesized on the ribosomes attached to the endoplasmic reticulum. It
flows into the endoplasmic reticulum in the form of dilute solution. The endoplasmic reticulum.
buds offsmall vesicles containing the product. These vesicles fuse with the cisternae of Golgi
complex, Thus the products transported othe cistemae of Golgi complex. In the cisternae, the
product is concentrated. The cisternae release secretory vesicles. The secretory vesicle is
loaded with the product. The product is released out of the cell by exocytosis.
| 7, Mucous Secretion
‘The intestinal cells (goblet cells) secrete mucous into the lumen of intestine, The mucous is
synthesized by the Golgi complex of goblet cells and is then secreted into the intestine. Mucous
secretion involves the following steps.
‘Protein i synthesized on the ribosomes of endoplasmic reticulum.
‘The protein move into the lumen of endoplasmic reticulum.
rom the endoplasmic reticulum, the proteins are packed in small vesicles.
‘© These vesicles are transported tothe cis «face ofesternae (Golgi complex).
‘The vesicles fuse with the cistemae,
* The proteins are transported from one cisterna to other towards the trans- face,

v

10. like

‘During this transport, the proteins are ghcasplatedbythe of sugars like galactose,

SEE nenne true
A A ph

are ci se ar distal end becomes
mon a uma inte sal endo isa ante dsl

rounded off to form mucigen granules.
The mucigen granules detach from the cisternae
* They move towards the plasma membrane. re.
They fuse with the plasma membrane and the mucigen granules are released into th

lumen of intestine by exocytosis.

\ es

Gag” OF @> 6

er

Fig.14.15: Mucous secretion.

8«Concentration and Storage of Secretory Products
The Go nae have the ability to concentrate the sec
through then

The secretory vesicles can store the secretory product until the produ
Glycosylation

Glycosylation is drat
produces comple
#lycogen, eto.

randed.

sylation
has glycoproteins, mucopolysaccharides, glycolipids,

Ribosome

Glycoprotein

u
LT)

ar Golgi cistema

Protein Endoplasmic
reticulum

Glycosyl Suga
transferase. resida

Fig.14.16: Glycosylation of proteins.

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11. The protein is synthesized in the ribosomes attached to endoplasmic reticulum. It
‘transported tothe cisternae of Golgi complex through the endoplasmic reticulum. The Golgi
‘complex also receives simple sugar molecules through the blood stream. The glycosyl transferase:
links sugar molecules to proteins to produce glycoprotein.

Thecistemae liberate secretory vesicles containing glycoprotein,

'Sulphation

Golgi complex is involved in: the metabolism of sulphate.

The goblet cells of intestine secrete mucigen. Mucigen is a mucopolysaccharide. Itis
made up of protein, sugar and sulphate. The Golgi complex adds sulphate tothe glycoprotein to
produce mucigen. Addition of sulphate is catalyzed by an enzyme called sulphotransferase
present inthe Golgi complex,

J" Lipid Packaging and Secretion

„einst cellsuse their Golgi apparatus forthe absorption of monoglycerides and fatty

The endoplasmic reticulum synthesizes triglycerides from monoglycerides and fatty acid
The Golgi complex concentrates and transport the lipids sythesizedin the endoplasmic reticulum
tothe plasma membrane and intercellular space.
12-Molecular Processing of Hormones

The polypeptide hormones are produced in an inactive form called prohormones. Eg.
Proinsulin proglucagon, etc. The prohormones are activated intracellularly bythe converting
enzyme present inthe Golgi complex.

Highlights

Functions of Golgi Complex
Golgi complex is a stack off flatened sacs and vesicles. It is a cell organelle.
+ They are the post office ofthe cell
+ They function as the ‘Receiving, Sorting and Shipping Departments’ of the
cell
+ They do the following functions
+ Cell secretion
+ Produce lysosomes.
+ Golgi of plant cells produce pectin and cell wall.
+ Plasma membrane formation.
+ Secretion of mucous
+ Secretion of saliva.
+ Secretion of sweat by sweat glands.
+ Secretion of il by oil glands
+ Secretion of tear by tear glands
+ Secretion of enzymes by exocrine glands.
+ Secretion of hormones by endocrine glands.
+ Secretion of antibodies by plasma cells

CB & MB-15

12. + Renewal Selene ‘membrane.

+ Glycosylation of lipids and proteins
+ Cell wall formation.

+ Processing of hormones.

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