What is the rough endoplasmis reticulum?

Answer 1

The rough endoplasmic reticulum is a network of membranesin the cytoplasm of eukaryotic cells.

The membranes enclose a continuous cavity, the lumen, that is separated from the cytoplasm. The lumen of the rough endoplasmic reticulum is continuous with that of the smooth endoplasmic reticulum and with the nuclear envelope.

The term "rough" applies to the appearance of the membranes under the electron microscope. They have small, more or less spherical spots attached to them; these are ribosomes. The ribosomes are the sites of polypeptide synthesis. All polypeptides are initially synthesized at free ribosomes in the cytosol, but certain amino acid sequences stimulate special molecules to transfer the ribosomes to the rough endoplasmic reticulum, where polypeptide synthesis continues, with the ribosome embedded in the membrane of the endoplasmic reticulum, and the polypeptide formed in the lumen of the endoplasmic reticulum.

Polypeptides synthesized in the rough endoplasmic reticulum form proteins that are destined for secretion or for certain locations within the cell, including the plasma membrane, lysosomes, or the endoplasmic reticulum itself.

The rough endoplasmic reticulum also transports materialsthrough the cell. The lumen forms a series of channels through which these materials can move from one place in the cell to another without entering the cytoplasm.

Answer 2

The endoplasmic reticulum (ER) is an eukaryotic organelle that forms an interconnected network of tubules, vesicles, and cisternae within cells.

The endoplasmic reticulum serves many general functions, including the facilitation of protein folding and the transport of synthesized proteins in sacs called cisternae.

Correct folding of newly-made proteins is made possible by several endoplasmic reticulum chaperone proteins, including protein disulfide isomerase (PDI), ERp29, the Hsp70 family member Grp78, calnexin, calreticulin, and the peptidylpropyl isomerase family. Only properly-folded proteins are transported from the rough ER to the Golgi complex.

Transport of proteins

Secretory proteins, mostly glycoproteins, are moved across the endoplasmic reticulum membrane. Proteins that are transported by the endoplasmic reticulum and from there throughout the cell are marked with an address tag called a signal sequence. The N-terminus (one end) of a polypeptide chain (i.e., a protein) contains a few amino acids that work as an address tag, which are removed when the polypeptide reaches its destination. Proteins that are destined for places outside the endoplasmic reticulum are packed into transport vesicles and moved along the cytoskeleton toward their destination.

The endoplasmic reticulum is also part of a protein sorting pathway. It is, in essence, the transportation system of the eukaryotic cell. The majority of endoplasmic reticulum resident proteins are retained in the endoplasmic reticulum through a retention motif. This motif is composed of four amino acids at the end of the protein sequence. The most common retention sequence is KDEL (lys-asp-glu-leu). However, variation on KDEL does occur and other sequences can also give rise to endoplasmic reticulum retention. It is not known if such variation can lead to sub-endoplasmic reticulum localizations. There are three KDEL receptors in mammalian cells, and they have a very high degree of sequence identity. The functional differences between these receptors remain to be established.

Other functions

• Insertion of proteins into the endoplasmic reticulum membrane: Integral membrane proteins are inserted into the endoplasmic reticulum membrane as they are being synthesized (co-translational translocation). Insertion into the endoplasmic reticulum membrane requires the correct topogenic signal sequences in the protein.
• Glycosylation: Glycosylation involves the attachment of oligosaccharides.
• Disulfide bond formation and rearrangement: Disulfide bonds stabilize the tertiary and quaternary structure of many proteins.
• Drug Metabolism: The smooth ER is the site at which some drugs are modified by microsomal enzymes which include the cytochrome P450 enzymes.

Answer 3

The rough endoplasmic reticulum(RER) is concerned with the transport of proteins which are synthesised by the ribosomes present on their surface. The name "rough endoplasmic reticulum" is because it looks rough under a microscope due to the ribosomes...

Answer 4

Rough endoplasmic reticulum is a cell organelle that helps in protein synthesis as well as packaging of materials into lysosomes and secretory activities of cell.

Answer 5

the rough er are attached to areas on the rough er

Answer 6

Rough Endoplasmic Reticulum is the surface on which ribosomes bind for protein synthesis.

Answer 7

rough endoplasmic reticulum, or rough ER is ER that has ribosomes attached to its surface, and helps to move them throughout the cell.

Answer 8

Ribosome