Golgi apparatus ppt (introduction structure and Function)

cell organelle Golgi apparatus ppt presented in American University of Barbados

1. By :- Chandani Kumari Yogesh Vishwakarma

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. Secretory material smooth endoplasmic reticulum transport vesicles golgi complex.  

6. 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.

7. 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 .

8. PATHWAY: Proteins and lipids Cluster of fused vesicles       Cis face     Modified into functional molecules and marked for delivery

9. FUNCTIONS SECRETION SYNTHESIS SULFATION APOPTOSIS PHOSPHORYLATION

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

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

12. 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.

13. 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

14. 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)

15. 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 .

16. 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

17. 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 .

18. 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.

19. Transport from the Golgi apparatus Transport from golgi takes place by two pathways. Constitutive secretory pathway Regulated secretory pathway

20. 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.

21. 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. .

22. 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

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