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The membrane-bound ribosomes specialise in the synthesis of proteins.

The Rough Endoplasmic Reticulum is an organelle inside of any eukaryotic cell.

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From rags to riches- The history of the endoplasmic reticulum.

Biology Lecture - 22 - Endoplasmic Reticulum
0:00mins-2:25mins, general discussion of endoplasmic reticulum; location in cell, superficial differences between smooth and rough ER.

The rough endoplasmic reticulum got its name because of its rough-looking texture.

The endoplasmic reticulum (ER) is an important in . It plays a major role in the production, processing, and transport of and . The ER produces transmembrane proteins and lipids for its membrane and for many other cell components including , secretory vesicles, the , the , and .

Structural organization of the endoplasmic reticulum.

On the surface of the cisternae are ribosomes, small organelles responsible for protein synthesis.

can be found in any eukaryotic cell (plant & animal)

Has a rough looking appearance because of ribosomes

Always attached to the Smooth ER and Nuclear envelope

Is a series of flattened sacs

Parts: -Ribosomes: Rough-looking organelles attached to R.E.R., responsible for protein synthesis
-Cisternae: flattened sacs that make up the membrane
-Lumen: The space inside the ER

Functions: Synthesizes & Packages Proteins and membranes for transport throughout the cell.

Without it, other organelles would not function properly because they do not have the proteins that were synthesized by the R.E.R.

Therefore, without the R.E.R, proteins would not be synthesized and transported throughout the cell, which would make other organelles and the cell as a whole stop functioning properly.

Protein folding in the endoplasmic reticulum Protein synthesis

The Rough ER plays a major role in the synthesis and packaging of proteins.

Larger amount in cells that produce lipids and steroid hormones.
To Put It Simply...
Quality Control
The biosynthesis of secretory and membrane proteins in the ER usually produces properly folded and biologically functioning proteins.

(Burchell A, 1996)
In addition to its roles in the processing of secreted and membrane proteins, the SER is also the major site for membrane lipid synthesis.

The Rough Endoplasmic Reticulum plays a large role in protein synthesis.
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  • The Structure and Function of the Endoplasmic Reticulum

    When the protein is complete, the rough endoplasmic reticulum pinches off a vesicle, which is a small membrane bubble.

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    The endoplasmic reticulum as the extracellular space inside the cell: role in protein folding and glycosylation.

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    Role of endoplasmic reticulum stress response in metabolism regulation [Online].

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Primary Role for Endoplasmic Reticulum-bound …

These cells are involved in protein synthesis, protein storage, transformation of carbohydrates, and synthesis of cholesterol, bile salts and phospholipids among other biological functions.
Homeostasis - The maintenance and regulation of internal conditions such as temperature or pH.
Hydrophilic - Any molecular entity which is attracted to, and soluble in water.
Hydrophobic - Any molecular entity which repels water.
Hypoglycemia - A medical state characterised by low concentrations of glucose in the blood.
Hypoxia - A medical state characterised by low concentrations of oxygen in any region of the body
Lumen - The inside space of a tubular structure
Mannose - A 6 carbon sugar monomer.
Mutation - Changes in the structure of a gene which will be transmitted to subsequent generations.
N-terminal - The end of a polypeptide which terminates at the amino group.
Nuclear envelope - A double lipid membrane which surrounds the nucleolus and genetic material.

role for the ER cellular protein synthesis.

Cells which are involved in secreting large amounts of protein are rich in rough ER, while steroid synthesizing and muscle cells are rich in smooth ER.

Role of Endoplasmic Reticulum in Biosynthesis of ..

Overall, increased GRP78 expression leads to the increased chaperone capacity of the ER, activation of these 3 proteins and their eventual re-association when homeostasis is restored.
(Schönthal 2012)

IRE1 plays a role in:
Protein folding
Expansion of ER membranes

ATF6 plays a role in:
Protein folding
Protein secretion

PERK plays a role in:
Apoptosis via activation of CHOP
Translational attenuation

This is the initial stage after activation of the UPR which prevents the further translation of proteins into the ER to avoid further accumulation of misfolded or unfolded proteins.

This involves the activation of PERK which phosphorylates eukaryotic initiation factor 2 alpha (eIF2) which in turn decreases protein synthesis and thus prevents the influx of proteins into the ER.

IRE1 leads to the translation of transcription factors that control the expression of genes involved protein folding.

ATF6 stimulates expression of a number of genes whose protein products contribute to protein folding such as GRP78 and GRP94.

As mentioned previously, IRE1 is activated during ER stress.

It is an enzyme which cleaves a 26-baase fragment from the mRNA encoding X box-binding protein 1 (XBP1).

Role of endoplasmic reticulum stress in the …

Mitogen-activated protein kinases (MAPK) are wellknown to be involved in mediating cell survival. The role of ERKhas been controversial in which its activation could result in cellproliferation and cell death. It was reported that the activationof ERK could be a result of DNA damage that subsequently leads tocell cycle arrest and apoptosis (,).In addition, ERK activation has been suggested to be a response tocounteract endoplasmic reticulum (ER) stress-induced apoptosis(,), which could be induced by externalstimuli such as cytotoxic agents. While there are studies on theability of triptolide to modulate the MAPK signaling pathways(,,),data on the effect of triptolide on ERK activation and subsequentcellular responses remain limited. Recently, triptolide has beenshown to induce the generation of reactive oxygen species (ROS) andnitric oxide leading to apoptosis in macrophage-like cell lines() as well as in colorectalcancer cell lines (). Given theability of intracellular ROS to activate ERK and subsequentapoptosis (–), it would be of interest toinvestigate if triptolide-induced apoptosis involves ROS generationand ERK activation.

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