Golgi complex

The Golgi complex
#Biology
#zoology
#Botany
#Cell biology
#Cell organelles
Golgi body, Golgi complex, Dictyosomes

1. GOLGI COMPLEX PRESENTED BY, SRUTHI C J

2. WHAT are golgi APPARAtUS ??? Also known as Golgi body , Golgi apparatus, Dalton Complex, Baker’s bodies, Carbohydrate factory . Seen in eukaryotic organisms. Function : Moves molecules from the endoplasmic reticulum to their destination. Modifies products to their final form.

3. GOLGI APPARATUS Made up of series of flattened , stacked pouches called CISTERNAE . Part of endomembrane system. Responsible for transporting , modifying and packaging proteins and lipids into vesicles for delivery to target destinations. Location: In the cytoplasm next to ER & near the cell nucleus . Contains set of glycosylation enzymes .

4. discovery One of the first organelles to be discovered. Discovered by Italian physician Camilo Golgi . Identified it in 1897 and named after him in 1898. During an investigation of nervous system . Termed the structure as “ apparato reticolare interno ”(internal reticular apparatus).

5. Early references to Golgi: Golgi-Holmgren duct. Golgi- kopsch apparatus. Golgi body(1910) Golgi apparatus(1956)

6. Sub cellular LOCALIZATION Varies among eukaryotes. Commonly seen near ER . Mammals - near the cell nucleus close to centrosome. Tubular connections are responsible for linking the stacks together. Saccharomyces cerevisiae(yeast) – scattered throughout cytoplasm. Plants – not concentrated at the Centrosomal region. do not form Golgi ribbons .

7. CHEMICAL COMPOSITION Chemically unstable . Lipoprotein composition. Laminar structure. Fluid mosaic organization. Formed mainly of proteins & phospholipids(6:4). Low levels of cholesterol esters, carotenoids , free fatty acids , triglycerides , mono saccharides, vitamin C etc reported in several cases. Rich in variety of enzymes (Thiamine pyrophosphatases , Glycosyl transferases)

8. Glycosyl transferases – Transfer oligosaccharides to proteins & lipids — thus mediates the synthesis of Glycoproteins & Glycolipids. Some acid phosphatases (ATPase , ADPase & CDPase ),Phospholipases, Oxidoreductase ,Transferases and some lysosomal enzymes may also found.

9. occurrence Occurs in all plant cells and animal cells such as mature sperm, RBC , mature sieve tubes etc. Absent in Mycoplasma,Blue green algae and other unicellular forms.

10. morphology Varies from cell to cell. 3 kinds – 1. LAMELLAE (core unit). 2. VESICLES 3. VACUOLES No attached ribosomes. ZONE OF EXCLUSION – Zone of clear cytoplasm surrounding Golgi body. - Glycogen,Ribosomes & Mitochondria are absent. Crowded around lamella

11. LAMELLAE Lamellae - Flattened sacs with dilated ends - They are arranged in parallel stacks or piles – GOLGIOSOMES . - Internal lumen of Lamellae – CISTERNAE . - Polarized orientation. - Convex outer face “ FORMING FACE or ENTRY FACE or CIS FACE” (Receiving dept) - Concave inner face “ MATURING FACE or EXIT FACE or TRANS FACE ”(Shipping dept)

12. Lamellar stack contain 3 major kinds of sacs 1. Cis sacs - towards cis face . - Phosphorylation of mannose molecules of glycoproteins. 2. Medial sacs - towards middle of stack. - Removal of mannose molecules(mannosidase) - Addition of acetyl glucosamine to glycoproteins. 3. Trans sacs - towards trans face . - Addition of galactose & sialic acid to glycoproteins.

13. Transition vesicles between cis face and RER . Origin : RER . Floats in cytoplasm. GA absorbs. Released as secretory vesicles -moves towards cell membrane-release. Also called transport vesicles .

14. vesicles Small membrane bound spaces . Composition and functions not definitely known. Occur in 2 forms – 1. Smooth-surfaced vesicles . 2. Rough-surfaced vesicles (coated vesicles) - coated with granules or bristles. VACUOLES Large membrane bound & scattered sacs . Composition not definitely known.

15. 2 forms – 1. Localized form . 2. Diffused form . LOCALIZED FORM: –Golgi complex occurs singly. -Occupies a fixed position between nucleus & secretory pole. -Found in polarized cells of vertebrates (Cells having base and apex) - Eg : Thyroid cells , Exocrine cells of pancreas & Mucous cells of intestine.

16. 2. DIFFUSED FORM : - Golgi complex found scattered along with the elements of ER. - Each unit is called DICTYOSOME . - Eg : Nerve cells & Liver cells (50 Dictyosome ), Most plant cells and cells of Invertebrates.

17. shape Variable in different types of somatic cells. Constant with each cell type.

18. DID YOU KNOW????? Paramoeba – 2 GA. Liver cells – 50 GA. Algal rhizoids – 25000 GA. Plant cells have multiple GA.

19. SIZE Variable . Large in Nerve and Gland cells . Small in Muscle cells . Well developed in active state of cells. Diminishes in size and disappears when cell become old.

20. position Cells of ectodermal origin – Between nucleus and periphery. Secretory exocrine cells – Between nucleus and secretory pole. Endocrine glands – variable. Thyroid – oriented towards center. Ganglionic cells of mouse – perinuclear(around the nucleus).

21. structure Major organelle in eukaryotic cells. Sac like . Found in cytoplasm of plant and animal cells. Composed of stack of membrane bound structures called CISTERNAE . Individual stack of cisternae – DICTYOSOME . Animal cells – 40 to 100 stacks. In a stack – 4 to 8 Dictyosome .

22. CISTERNAE – Disc enclosed in a membrane. - Possess special enzymes. - Helps to modify & transport of proteins to their destination. Bent and semicircular shape. Polar in nature.

23. Secretory pathway(OVERVIEW) 2 Different secretory pathways --- 1. Regulated pathway. 2. Constitutive pathway. Regulated pathway – Proteins consolidated into vesicles and stored in the cell until they are secreted in response to specific signal. Constitutive pathway – Vesicles continuously form and carry proteins from Golgi to the cell surface.

24. Endocytic pathway(overview) External proteins bind to receptors in plasma membrane. Incorporated into vesicles . Carried to early endosomes . Receptors are separated and returned to cell surface. Early endosomes – Moves to late endosomes – Lysosomes – Proteins are digested by the Lysosomal activity. Deals with 2 terms – 1. Phagocytosis . 2. Pinocytosis .

25. Phagocytosis – Ingestion of large particles by cells through phagosomes or vacuoles . Eg:Macrophages or protists ( Amoeba,Paramecium ) 2. Pinocytosis – Ingestion of fluid and macromolecules through small vesicles . Eg : Performed by all cells.

26. FUNCTION Modify,sort & package of macromolecules synthesized by cell for secretion purpose. Mainly modifies proteins from ER . Transport of lipids around cell. Create lysosomes (GERL Concept) Referred to as POST OFFICE where molecules are packaged, labelled and sent to different parts of cells. Enzymes in cisternae - ability to modify proteins by the addition of carbohydrates( Glycosilation ) and phosphates( Phosphorylation ).

27. Modification of proteins – GA imports some substances like nucleotides from cytosol - signal sequence – determines the final destination of proteins. Production of PROTEOGLYCANS . (Molecules that are present in extracellular matrix of animals). Major site of synthesis of carbohydrates . Involves in the sulfation (method by which esters or salts of sulphuric acid are formed).

28. golgiogenesis Formation and differentiation of Golgi body during embryonic development .

29. golgiokinesis Division of Golgi apparatus during Nuclear division.

30. golgisomes Corpuscles produced by Golgiogenesis .

31. golgiolysis Dissolution of Golgi apparatus.

32. golgiorrhexis Fragmentation on Golgi apparatus.

33. What’s new????? GA composed of lipo-protein spheres . Primary function of spheres- To protect the cell by producing noxious( harmful,poisonous ) substances.

34. summary Critical member of biochemical manufacturing and supply chain inside cell. Only organelle that receives,sorts,modifies,concentrates,packs and dispatches biochemicals. Specialized secretory cells of Golgi sort and pack Insulin,digestive enzymes and pectin. Products of GA goes to 3 main destination : 1 .Inside the cell of lysosomes . 2 .The plasma membrane . 3 . Outside the cell .

35. WHAT TO REMEMBER??? Camilo Golgi(1897) Morphology-Lamellae( Cisternae,Dictyosomes ), Vesicles,Vacuoles . Golgiosomes . Cis face ,Trans face ,Cis sac ,Medial sac ,Trans sac. Zone of exclusion. Chemical composition. Functions. Golgiogenesis .

36. Expected questions Golgi body was identified by --------? Golgi bodies are made up of series of flattened stacked pouches called -------? Functions of Golgi body in short. Golgi bodies are chemically --------? Which of the cell organelle is known as traffic police of cell? Dictyosomes are ---------? Camilo Golgi discovered GA in which cells? What are 2 types of secretory pathway ? Explain. What is endocytic pathway? Write short note on chemical composition of Golgi complex. Write short note on morphology of Golgi complex. Write short note on functions of Golgi complex. What is Golgiogenesis ?