The document discusses the endoplasmic reticulum (ER), which is a network of membranous tubules and sacs that transports materials within cells. There are two types of ER - rough ER and smooth ER. Rough ER is prominent in cells that produce large amounts of proteins and has ribosomes attached. Smooth ER is involved in lipid and steroid synthesis and does not have ribosomes. The ER helps transport molecules within cells, provides structure, and is involved in processes like protein transport and modification, lipid and steroid synthesis, and breaking down toxic substances.

1. ENDOPLASMIC RETICULUM
STRUCTURE AND FUNCTIONS
DR. DILIP V. HANDE
ASSOCIATE PROFESSOR, DEPT OF BOTANY
SHRI SHIVAJI SCIENCE COLLEGE, AMRAVATI MS.

2. INTRODUCTION
 Endoplasmic reticulum is double membrane
network system observed for the first time by
Porter, Claude & Fullan (1945) in the
cytoplasm.
 Later on in 1953 Porter & Kallmon termed it
as Endoplasmic Reticulum .
 It is an finely divided complex vascular
system extending from the outer nuclear
membrane passing through cytoplasm to
plasma-membrane.
 It is a network of cisternae, tubules &
vesicles.

3. Endoplasmic Reticulum - ER
 Network of hollow membrane tubules
 Connects to nuclear envelope & cell
membrane
 Functions in Synthesis of cell products
& Transport
copyright cmassengale 3Two kinds of ER ---ROUGH & SMOOTH

4. Rough Endoplasmic Reticulum
 Ribosomes attached to surface
◦ Manufacture protiens
◦ Not all ribosomes attached to rough ER
 May modify proteins from ribosomes

5. Rough Endoplasmic Reticulum
(Rough ER)
 Has ribosomes on
its surface
 Makes membrane
proteins and
proteins for
EXPORT out of cell
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6. Rough Endoplasmic Reticulum (Rough
ER)
 Proteins are made
by ribosomes on
ER surface
 They are then
threaded into the
interior of the
Rough ER to be
modified and
transported
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7. Smooth Endoplasmic Reticulum
 No attached ribosomes
 Has enzymes that help build molecules
◦ Carbohydrates
◦ Lipids

8. Smooth Endoplasmic Reticulum
 Smooth ER lacks
ribosomes on its
surface
 Is attached to the
ends of rough ER
 Makes cell products
that are USED
INSIDE the cell
copyright cmassengale 8

9. Functions of the Smooth ER
 Makes membrane
lipids (steroids)
 Regulates calcium
(muscle cells)
 Destroys toxic
substances (Liver)
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10. Endomembrane System
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Includes nuclear membrane connected to ER
connected to cell membrane (transport)

11. STRUCTURE

12. Occurrence
 It is almost found in all Eukaryotic
cells and more distinct in young
meristematic cells, the amount of
E.R. varies from cell to cell.
 It is found more in amount in those
cells which are active for protein
synthesis.

14. Types
Smooth or Agranular E.R. (SER):-
 The membrane of smooth E.R. are not granular
due to absence of ribosomes .
 It is more abundant near the peripheral part of
the cytoplasm & may found attached to the
plasma-membrane.
 It forms the transport vesicles in which large
molecules (protein & lipid) are transported from
one cell to other through plasmodesmata.
 Rough or granular E.R.(RER )
 The rough E.R. has granular surface due to the
presence of large number of ribosomes attached
to it.
 These are found more abundant in deeper part of
cytoplasm near the nucleus where it is connected
to outer nuclear membrane. It is active protein
synthesis.

16. Structure :
 Morphologically the E.R. consist of three
types of structures. i.e. cisternae. vesicles
and tubules.
 Cisternae :
 The cisternae are elongated, cylindrical,
unbranched flattened sac like lie parallel
to each other.
 These are interconnected with each other
and 40-50 A0 diameter.
 Generally they bears ribosomes on their
cytoplasmic faces and found in cell active
in protein synthesis.

17. Endoplasmic Reticulum
17

18. STRUCTURE
 Tubules :
 These are tube like extension generally connected to
cisternae.
 These are smooth and free from ribosomes.
 The tubules are irregular branching elements
which form network.
 It is having 50- 500 A0 diameter and active in
synthesis of steroid, cholesterol, glycerides.
 Vesicles :
 These are sac like or oval bodies, occur freely in the
cytoplasmic matrix.
 These are also lacking ribosomes. The diameter is
about 25-50 A0

21. Cell Parts and Functions
Endoplasmic Reticulum (E.R.)
Transports materials and sends messages to
all parts of the cell
Two types: smooth and rough (has
ribosomes)
Location: attaches from cell membrane to
nuclear membrane
Rough E.R.

22. STRUCTURE
 E.R. membrane :- The membrane is lipo-
proteinous in nature which encloses the
matrix of E.R.
 It is 50-60 A0 in thickness.
 Various enzymes are associated with E.R.
are stearases, NADH- cytochrome. C-
reductase, Mg++ activated ATPase & other
enzymes like of glycerides, fatty acids, L-
ascorbic acid and steroid metabolism.

23. Endoplasmic Reticulum
 Structure: a system of membranous tubules
and sacs
 Function: intercellular highway (a path along
which molecules move from one part of the cell
to another)
 Two types:
◦ Rough Endoplasmic Reticulum
◦ Smooth Endoplasmic Reticulum

24. Rough Endoplasmic Reticulum
 Rough Endoplasmic
Reticulum (rER):
prominent in cells that
make large amounts of
proteins to be exported
from the cell or inserted
into the cell membrane
◦ Covered with ribosomes

25. Smooth Endoplasmic Reticulum
 Smooth Endoplasmic
Reticulum (sER):
involved in the synthesis
of lipids and breakdown
of toxic substances
◦ Not covered with
ribosomes

26. Functions :
 The network of E.R. separates cytoplasm into
several small compartments which helps the
cell to perform specific activities by providing
enzymes and metabolites within specific
chambers excluding others.
 E.R. given mechanical support to cytoplasm
to provides a kind of inter cellular
cytoskeleton to maintain the form of cell and
keeps cell organelles distributed properly in
relation to one another.
 E.R. has osmotic properties and it is involved
in intra- cellular exchange of materials
particularly between the cytoplasm and the
nucleus.
 E.R. helps in membrane formation in
eukaryotic cell. It play a role in synthesis of
new nuclear membrane using cell division.

27. Functions :
 E.R. serves as circular system for the
transportation of cellular molecules and helps
in the storage of synthesized molecules.
 The enzymes of smooth E.R. involve in the
synthesis of cholesterol their conversion into
the steroid hormone.
 Rough E.R. play a role in protein synthesis
and some specific proteins synthesized by
ribosome when enter into E.R. lumen and
they get modified.
 Some enzymes of E.R. e.g. cytochrome P
450 convert lipid soluble molecules of drugs
into the water soluble molecules.

28. THANKS