STRUCTURE AND FUNCTION OF ENDOPLASMIC RETICULUM AND GOLGI APPARATUS.

2. HISTORY
Electron microscope has revealed an
extensive membrane system in the
cytoplasm, called endoplasmic reticulum,
first reported by Porter in 1945. This
continuous membrane system joins the
nuclear membrane on one end and the
cell membrane on the other.

3. Distribution
ER is absent in prokaryotes. In
eukaryotes, it is generally absent from
egg and embryonic cells. In
spermatocytes, though present, it is
poorly developed. Generally ER is fully
developed in cells actively engaged in
protein and hormone synthesis. The size
and shape of the ER changes with the
type of cells in which

4. STRUCTURE
ER is composed of three different types of
three different types of structures These are-

5. 3. Tubules
They are irregular branched tube like structures
having a diameter of 50 to 500 µm. These structures
are surrounded by thin unit membrane of 50 - 60Å
thickness and their lumen is filled with secretory
product of the cell.

6. FUNCTIONS
1. Functions common to both smooth and rough ER.
(1) Forms skeletal framework.
(2) Active transport.
(3) Metabolic activities due to enzymes.
(4) Provide increased surface area.
(5) Formation of new nuclear membrane during cell division.

7. 2. Function of smooth ER
(1) Lipid synthesis.
(2) Glycogen synthesis.
(3) Steroid (like cholesterol, progesterone, testosterone, etc)
synthesis.
3. Function of rough ER
(1) It provides site for protein synthesis.
(2) It helps in transport of proteins.

8. HISTORY
Italian zoologist, Camillo Golgi (1898) observed
Golgi complex for the first time. This Organelle is
known by several names – Golgi apparatus,
Golgi body, Golgi material, Golgi membrane,
Golgiosome, etc. In plants and lower
invertebrates, it is usually called dictyosome.

9. Distribution
Golgi apparatus is present in all the eukaryotic
cells but is absent from prokaryotic cells.
Amongst eukaryotes, Golgi complex is not
found in the cells of fungi, male gametes of
bryophytes and pteridophytes. mature sieve
tubes, and mature sperms and red blood cells
of animals.

10. STRUCTURES
In plants cells, the Golgi apparatus measures about 1-3µm
in length and about 0.5µm, in height. It also consists three
main parts
1. Cisternae
Which form the central flattened or disc shaped part of
Golgi complex, are stacks of parallel double membranes or
lamellae. Each membrane is 60 to 70 Å thick. There is a
space of 60 – 90 Å in between the two membranes. There is
little or no continuity between adjacent cisternae and they do
not have a collecting bounding membrane

11. 2. Tubules
Arise from the periphery of the cisternae and form
a highly branched anastomosing network. Their
diameter varies from 300 - 500Å.
3. Vesicles
They are of two types-
(i) Rough vesicles present at the ends of
cisternae. They are about 500Å in diameter.
(ii) Smooth vesicles usually present within the
network or sometimes near the centre of the
stack of cisternae. Their diameter varies from
200 to 800Å.

12. The Golgi apparatus shows a complex network
of tubules and vesicles towards the periphery. The
organelle has a definite polarity. Both the faces differ
from one another. The convex face is called forming
face or cis region. It is associated with ER. The
concave face is called maturing face or trans region.
Golgi apparatus forms an extensive
intercommunicating membrane system in association
with cell membrane, endoplasmic reticulum, lysosome
and nuclear membrane. It is also called
endomembrane system.
Golgi apparatus is very rich in phospholipids,
proteins, various enzymes, carotenoids, fatty acids
and vitamin C.

13. FUNCTIONS
The following are the major functions of Golgi apparatus.
(1) Synthesis of poly saccharides.
(2) Formation of glycoproteins by combining carbohydrates
with proteins.
(3) Synthesis of pectins and other carbohydrates necessary
for cell wall formation. Secretory vesicles of Golgi
apparatus fuse and get incorporated into cell
membrane. Similarly in the plant cells, Golgi apparatus
deposits pectic substances and cellulose microfibrils to
form a cell plate during cell division.

14. 4) It is also secretes gum and
mucilage.
(5) It is associated with storage,
condensation, packaging and
transportation of various substances.
(6) It is also active in the formation of
one type of membrane into another.
(7) Secretory vesicles and lysosome
originate from Golgi apparatus.

15. THANK YOU