THE

ENDOMEMBRANESYSTEM

PRESENTED BY AINDRILA MAJUMDAR(BIOTECHNOLOGY-1ST YEAR)

1.INTRODUCTION2.GOLGI APPARATUS-DEFINITIO1N -DISCOVERY-DISTRIBUTION AND NUMBER-ORIGIN-ULTRASTRUCTURE -CHEMICAL COMPOSITION-FUNCTIONS OF GOLGI BODY

TOPICS

TO BE

DISCUSSED

THE ENDOMEMBRANE SYSTEM IS COMPOSED OF

DIFFERENT MEMBRANES THAT ARE SUSPENDED IN

THE CYTOPLASM WITHIN A EUKARYOTIC CELL.

THESE MEMBRANES DIVIDE THE CELL INTO

FUNCTIONAL AND STRUCTURAL COMPARTMENTS OR

ORGANELLES, EITHER BEING CONNECTED DIRECTLY

OR EXCHANGING MATERIAL THROUGH VESICLE

TRANSPORT. IN EUKARYOTES ENDOMEMBRANE

SYSTEM INCLUDE:

- NUCLEAR ENVELOPE

- ENDOPLASMIC RETICULAM (ER)

-GOLGI APPARATUS

-LYSOSOMES

INTRODUCTION

GOLGI BODY

DEFINITION: GOLGI BODY IS A SMOOTH SURFACED, RETICULAR, MEMBRANE ENCLOSED ORGANELLE OF EUKARYOTIC CELLS CONCERNED WITH SECRETION.DISCOVERY: CAMLLIO GOLGI (1898), AN ITALIAN BIOLOGIST FIRST OBSERVED THIS IN NERVE CELLS,BY SILVER STAINING METHOD & NAMED AFTER HIM, OTHER SCIENTISTS CALL IT BY VARIOUS NAMES SUCH AS GOLGI COMPLEX, LIPOCHONDRIA, DICTIOSOMES.

DISTRIBUTION AND NUMBER: FOUND IN ALL EUKARYOTIC CELLS EXCEPT A FEW INCLUDING MAMMALIAN RBC. GENERALLY, IN SECRETORY CELLS, A LARGE SINGLE GOLGI BODY IS PRESENT BETWEEN NUCLEUS AND CELL MEMBRANE. EXAMPLES-THYROID CELLS, INTESTINAL MUCOSAL CELLS, etc. BUT IN LIVER CELLS, NERVE CELLS, MORE THAN ONE GOLGI MAY BE PRESENT.

ORIGIN: THE GOLGI BODY REMAINS CONNECTED WITH ER, AND SUPPOSED TO BE ORIGINATED FROM ER. PROBABLY AT FIRST,SMALL,MEMBRANE BOUND VESICLES ARE FORMEDBY BUDDING FROM SER,WHICH THEN JOIN AND FUSE TO FORM CISTERNAE. IN THE CELLS OF SOME LOWER PLANTS AND ANIMALS,THE GOLGI BODY MAY BE FORMED FROM THE NUCLEAR MEMBRANE AND CELL MEMBRANE .

ULTRASTRUCTURE: THE SHAPE OF GOGI

BODY CHANGES FROM TIME TO TIME.

THESE ARE OF THREE TYPES –

(I) CISTERNAE OR LAMELLAE: THESE ARE

MEMBRANE BOUND FLATTENED SACS

THAT REMAIN STACKED ONE ABOVE

ANOTHER . TWO ADJACENT CISTERNAE

ARE SEPARATED BY A SMALL GAP OF

ABOUT 20-30 nm. EACH STACK OF

CISTERNAE FORMING A DICTYOSOME IS

POLARIZED STRUCTURE HAVING A

PROXIMAL OR FORMING FACE(CONVEX)

AND DISTAL OR MATURING FACE

(CONCAVE).THIS POLARIZATION IS

OFTEN REFERRED TO AS CIS-TRANS

AXIS OF GOLGI COMPLEX.

(II) VACUOLES: THESE ARE THE SWOLLEN

AND VESICULAR TERMINAL PARTS OF

CISTERNAE.

(III) TUBULES & VESICLES: THE CONVEX

SURFACE OF THE CISTERNA REMAINS

CONNECTED TO A NETWORK FORMED

BY FINE,BRANCHED TUBULES. THE

CHEMICAL COMPOSITION: GOLGI BODY BEING AN

ORGANELLE MADE UP OF LIPOPROTEIN

MEMBRANE, ITS CHIEF CONSTITUENTS ARE

LIPID(PHOSPHOLIPID) AND PROTEIN. A FEW

ENZYMES LIKE thiamine-pyrophosphatase AND

SEVERAL glycosyl transferases.

FUNCTIONS OF GOLGI BODY:

(I) SECRETION AND TRANSPORT

(II) SYNTHESIS OF GLYCOSPHINGOLIPIDS AND

GLYCOPROTEINS & PACKAGING

(III) FORMATION OF OTHER ORGANELLES

(IV) FORMATION OF ACROSOMAL CAP OF SPERMS

(V) BIOGENESIS OF GOLGI BODY.

ZONE OF EXCLUSION: THE GOLGI COMPLEX REMAINS SURROUNDED

BY A ZONE OF CYTOPLASM WHERE MOST OF ORGANELLES ARE

ABSENT.

GERL SYSTEM: ASSOCIATED WITH TRANS FACE THERE IS OFTEN A

SACCULAR STRUCTURE THAT IS RICH IN ACID PHOSPHATASE & HAS

BEEN INTERPRETED AS A REGION OF SMOOTH ENDOPLASPIC

RETICULAM,NEAR THE GOLGI,INVOLVED IN THE PRODUCTION OF

LYSOSOMES.

*SECRETION:THE CHIEF FUNCTION OF GOLGI BODY IS SECRETION FROM A CELL OF PROTEIN MATERIALS e.g.,ENZYMES, HORMONES,NEUROTRANSMIITERS,etc. THAT ARE NOT EASILY DIFFUSABLE THROUGH CELL MEMBRANE. THE EXACT ROLE OF GOLGI BODY IN SECRETION IS TO FORM LIPOPROTEIN MEMBRANE BOUND VESICULR PACKETS OF THE SECRETORY MATERIAL.*GLYCOPROTEIN FORMATION: GOLGI BODY TAKES PART IN THE SYNTHESIS OF GLYCOPROTEIN (e.g. mucin) AND GLYCOSPHINGOLIPID MATERIAL . THE PROTEIN PART IN THESE MATERIALS ARE FORMED IN RER, AND THEN COMBINED WITH THE SUGAR DERIVATIVES IN GOLGI BODY TO PRODUCE GLYCOPROTEINS.*FORMATION OF OTHER ORGANELLS: THE CELL WALL AND CELL MEMBRANE CONTAIN VARIOUS GLYCOPROTEIN MATERIALS THAT ARE FORMED IN GOLGI BODY. THE GOLGI BODY ALSO HELPS IN THE FORMATION OF LYSOSOMES.*ACROSOME FORMATION: THE GOLGI BODY PLAYS AN IMPORTANT ROLE IN THE FORMATION OF OF ACROSOMAL CAP DUIRING SPERM MATURATION.

THE GOLGI IS AN ESSENTIAL MEMBRANE

BOUND ORGANELLE IN SECRETORY

PATHWAY OF EUKARYOTIC CELLS. IN

MAMMALIAN CELLS, THE GOLGI STACKS ARE

INTEGRATED INTO A CONTINUOUS

PERINUCLEAR RIBBON, WHICH POSSES A

CHALLENGE FOR THE DAUGHTER CELLS TO

INHERIT THIS MEMBRANE ORGANELLE

DURING CELL DIVISION. TO FACILITATE

PROPER PARTITIONING, THE MAMMALIAN

GOLGI RIBBON IS DISASSEMBLED INTO

VESICLES IN EARLY MITOSIS. FOLLOWING

SEGREGATION INTO THE DAUGHTER CELLS, A

FUNCTIONAL GOLGI IS REFORMED. HERE WE

SUMMARIZE OUR CURRENT UNDERSTANDING

OF THE MOLECULAR MECHANISMS THAT

CONTROL THE MITOTIC GOLGI DISSAMBLY

AND POSTMITOTIC RESSEMBLY CLCLE IN

MAMMALIAN CELL.

MECHANISM OF GOLGI BIOGENESIS :

THANK

YOU