golgi apparatus

1. By :- INAM UL HAQ

2. GOLGI APPARATUS

3. What is Golgi Apparatus ?
 Also known as Golgi complex, Golgi
body or Golgi.
 Membrane bound organelles, which are
sac-like.
 Found in cytoplasm of most eukaryotic
cells and absent in prokaryotes,
Mammalian RBCs and sperm cells of
bryophytes.
 Ranges from one to several within a cell.
 In plant cells several small Golgi complex
– dictyosomes.
 It is responsible for transporting,
modifying and packaging proteins and
lipids into vesicles.

4. Structure of Golgi Apparatus :-
 Is made up of several stack of
parallel, flattened sac or cisternae.
 Many peripheral tubules and
vesicles.

5. CISTERNAE
 Golgi apppartaus is made up of approx 4- 8 cisternae .
 Usually equally spaced in stark separated from each other
by thin layer of intercisternal cytoplasm .
 Golgi complex has a distinct polarity ,the two poles are cis
and transface responsible for receiving and shipping
departments.
Forming (cis)face-convex side of stack,Maturing(trans)face-
concave side of stack.
𝑓𝑟𝑜𝑚
• Secretory material smooth endoplasmic
𝑣𝑖𝑎 𝑟𝑒𝑎𝑐ℎ𝑒𝑠
reticulum transport vesicles golgi complex.

7. Tubules & vesicles :-
Tubules: - small, round tubules formed from the periphery of
the cisternae .
 And few get enlarged at the end to form vesicles.
Vesicles:-lie near the end and concave surface of the golgi
complex
 Types of vesicles:-smooth vesicles and coated vesicles
Golgi matrix:-all golgi elements filled with a fluid.

8. Modification in CGN AND TGN
 Two networks the Cis Golgi Network( CGN) and Trans Golgi Network
(TGN )are made up of outermost cisternae at the cis and trans face.
 Vesicles containing proteins from the endoplasmic reticulum (ER)
merge with the CGN and allowing protein to enter Golgi complex
 As CGN receives protein from the ER it begins there modification
moving along membrane to membrane towards the TGN .
 At Other end of Golgi complex , newly modified protein arrives at the
TGN where it is send off to different parts of the cell via transport
vesicles .

9. PATHWAY:
Proteins and lipids
Cluster of fused vesicles
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𝑑𝑒𝑙𝑖𝑣𝑒𝑟𝑒𝑑 𝑖𝑛𝑡𝑜 𝑙𝑢𝑚𝑒𝑛 𝑜𝑓 𝑐𝑖𝑠 𝑓𝑎𝑐𝑒 𝑐𝑖𝑠𝑡𝑒𝑟𝑛𝑎𝑒
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dinto functional
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10. FUNCTIONS
 SECRETION
 SYNTHESIS
 SULFATION
 APOPTOSIS
 PHOSPHORYLATION

12. SECRETION
 Golgi complex plays an important role in secretion.
 Production of proteoglycans

14. SYNTHESIS
It is also major site of carbohydrate synthesis .
Includes synthesis of glycoasaminoglycans (GAGs)
Golgi attaches to polysaccharides and protein
to form proteoglycans

15. SULFHATION
 Golgi involves in the sulfation of ceratain molecules passing
through lumen via sulphotransferases that gain sulphur
molecule from a donor called PAPS .
 Sulfation is generally performed in trans – Golgi network
 Sulfation occurs in GAGs of proteoglycans as well as core
protein
 Level of sulfation is very important to proteoglycans.

16. APOPTOSIS
 Golgi has a putative role in apoptosis
 A newly characterized protein (Golgi anti-apoptotic
protein) almost exclusively resides the Golgi and protects
cells from apoptosis
 As yet it is an undefined mechanism

18. PHOSPHORYLATION
 Phosphorylation of molecules require
energy in the form of ATP .
 The ATP is imported into the lumen of
Golgi which is utilized by casein kinase 1
and casein kinase 2 .
 Apolipoprotein – forms a molecule VLDL
(constituent of blood serum)

19. Protein glycosylation within Golgi
 Protein processing within golgi involves the
modification and synthesis of carbohydrate
portions of glycoprotein.
 One of the major aspects of this processing is
the modification of N-linked oligosaccharides
that were added to protein in ER .
SEQUENCE OF REACTION:
 Removal of 3 additional mannose residues
 Sequential addition of N-acetyl glucosamine
 Removal of 2 more mannoses
 Addition of fucose and 2 more N-acetyl
glucosamine .

20. LIPID AND POLYSACCHARIDE
METABOLISM
ceramide sphingomyelin
glycolipid
Phosphorylcholine group is
transferred from phosphatidylcholine
to ceramide
When one or more sugar residues or
added then alternatively a variety of
different glycolipids can be synthesized

21. Vesicular transport from ER
to Golgi bodies
 Process in which membrane –
enclosed transport vesicles
transport proteins from one
membrane-enclosed
compartment to another.
 Proteins doesn’t move across the
lipid bilayer instead only move
between topologically equivalent
compartment like- lumen of ER
to lumen of Golgi to exterior of
the cell.

22. Protein Sorting and Export from the Golgi
Apparatus
 Golgi apparatus transport proteins,
lipids and polysaccharides to their
final destinations  secretory
pathway
 Involves sorting of proteins into
different kinds of transport vesicles.
 Which bud from the trans Golgi
network and deliver their contents
to the appropriate cellular
locations.

23. Transport from the Golgi
apparatus
 Transport from golgi takes place by
two pathways.
1. Constitutive secretory pathway
2. Regulated secretory pathway

24. a. Constitutive secretory pathway
 Proteins are secreted from a
cell continuously, regardless
of external signals or
factors.
 Proteins are stored in
vesicles in the Golgi and
move directly to the cell
surface and fuse with the
PM and release the soluble
proteins.

25. b. Regulated secretory pathway:-
 A distinct regulated secretory pathway in
which specific proteins are secreted in
response to environmental signals.
 Proteins are sorted in trans Golgi network
and packed into secretory vesicles.
 These secretory vesicles are usually larger
than other transport vesicles.
 And stored until specific signals are
received , then fuses with plasma
membrane to release the proteins.
.

26. Selective transport of proteins to lysosomes
 The process of protein sorting in the
Golgi  lysosomes through selective
transport of proteins.
 Then proteins are modified by
‘mannose phosphorylation’  in cis
Golgi network.
 These phosphorylated mannose
molecules are specifically recognized
by a ‘mannose-6-phosphate receptor’
 in trans Golgi network

27. Questions ???
1. When a molecule enters the Golgi apparatus the molecule enters
through the and exits through the ?
ANSWER: cis face, trans face