The endoplasmic reticulum is a network of membrane-bound vesicles that traverse the cytoplasmic matrix. It was discovered in 1945 by Porter. There are three main structures of the endoplasmic reticulum: cisternae, vesicles, and tubules. Cisternae are long, flattened sacs that occur in cells with synthetic roles. Vesicles are oval, vacuolar structures. Tubules form a reticular system along with cisternae and vesicles. The endoplasmic reticulum is thought to originate from evaginations of the nuclear membrane. It comes in two types: rough endoplasmic reticulum with ribosomes attached, involved in protein synthesis, and smooth endoplasmic reticulum

1. DEPARTMENT OF BIOCHEMISTRY
PRESENTED BY—RAJNISH KUMAR
ROLL NO –02
CLASS --SEM1

2. ENDOPLASMIC RETICULUM
• The cytoplasmic matrix is traversed by a
complex network of inter-connecting
membrane bound vesicles. These vacoules
often remain concentrated in the endoplasmic
portion of the cytoplasm therefore known as
endoplasmic reticulum.
• Endoplasmic reticulum was discovered by
porter in 1945.

3. Morphology of endoplasmic reticulum
• Endoplasmic reticulum is composed of three
type of structures
• 1)cisternae – the cisternae are long, flattened,
sac like tubules having diameter of 40 to 50um
the cisternae usually occur in those cells
which have synthetic roles as the cells of
pancreas, notochord, and brain

4. • 2)Vesicles—the vesicles are oval, membrane
bound vacuolar structures having diameter of
25 to 500um. They often remain isolated in the
pancreatic cells.
• 3)Tubules– the tubules are branched
structures forming the reticular system along
with the cisternae and vesicles.

6. Origin of Endoplasmic reticulum
• The exact process of the origin of endoplasmic
reticulum is still unknown. But because
membrane of ER resembles with the nuclear
membrane and plasma membrane and also at
the telophase stage the ER membranes are
found to form the nuclear envelope. Therefore
it is assumed that the ER is originated by
evagination of nuclear membranes.

7. Types of endoplasmic reticulum
• 1) Rough endoplasmic reticulum– these type
of ER posses rough walls because the
ribosome remain attached with its membrane.
Ribosome play vital role in protein synthesis
• 2)smooth endoplasmic reticulum—these type
of ER ribosome are not attached with its
membrane so these are smooth. smooth ER in
synthesis of lipids

8. Function of endoplasmic reticulum
• Endoplasmic membrane contain many
enzymes which perform various synthetic and
metabolic activities
• ER also helps in storing synthesis and
metabolism of glycogen
• Smooth ER also synthesizes the steroid
compounds eg.. Cholestrol,glycerides
• Helps in the process of synthesis of protein

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