The ER is enclosed within the membrane and are only found in eucaryotes. It provides a connection between the nucleus and plasma membrane.
Cisternae, tubules and vesicles all three are present in the endoplasmic reticulum. The endoplasmic reticulum is a continuing structure of the nuclear membrane which creates a link between the nucleus and cytosol for the in-out movement of molecules.
Endoplasmic forms a network system and serves as the channel for transportation of materials throughout the cell and are also involved in the detoxification of harmful chemicals. It provides the cytoplasmic framework for biochemical reactions and also shows a very peculiar feature of membrane biogenesis.
Let us focus on, does endoplasmic reticulum contain cisternae and if yes so why do they possess that section, and which type of ER having this cisternae, what do they perform and many more questions in this article.
Does endoplasmic reticulum contain cisternae?
Cisterna is a folded, closed and flattened membrane playing a vital role in the packaging and processing of proteins through vesicles.
Yes, the endoplasmic reticulum is composed of cisternae. Mostly they adjoins the rough endoplasmic reticulum. Ribosomal granules adhere over it to synthesise proteins. It is absent in procaryotes and mammalian matured RBCs.
Cisternae is an unbranched, parallelly-arranged tubule connected from each other forming the sac-like structure. Cisternae are one of the important section of the endoplasmic reticulum. Cisternae are filled with a jelly-like structure known as an endoplasmic matrix.
Why does endoplasmic reticulum contain cisternae
Cisternae of rough endoplasmic reticulum followed by ER lumen is the site for protein folding, modifications, processing and assembly. Let us explore why ER is having cisternae.
The endoplasmic reticulum contains cisternae because they have to maintain the main framework of the structure. Cisternae will generally be restricted nearer to the cytosolic face of nuclear envelope and are kept intact by matrix proteins
This gives mechanical stiffness and a proper shape and size to the cytoskeleton. These cisternae possess some signal sequences to guide the newly formed proteins for cluster formation. They have some specific binding proteins for the attachment of ribosomes and also have an intramembrane multiprotein complex.
What type of endoplasmic reticulum contains cisternae
Cisternae are an integral part of the endoplasmic reticulum and are about 40-50 micrometres in diameter.
The rough endoplasmic reticulum contains cisternae. Cisternae is the structure that gives rise to RER having ribosomes. These ribosomes are attached with the help of ribophorin proteins. They are the ribosomal factory, a site for the production of proteins.
These ribosomes give a irregular appearance to the ER. The rough endoplasmic reticulum is abundantly found in hepatic and pancreatic cells. After the synthesis and post-translational modifications, these polypeptides are transferred to Golgi bodies for packaging and are ready to release out of the cell via vesicles to their target centres.
What does cisternae do in the rough endoplasmic reticulum
Cisternae are actively participated in the production of polypeptide chains and involved in providing mechanical strength to the cell.
Cisternae is chiefly liable for the transportation of early peptides in vesicles to the Golgi apparatus. Newly formed folded proteins like glycoproteins have to reach into Golgi bodies for packaging and further processing.
These protein packets are moved towards their destination in the form of clustering vesicles. Cisternae also participated in the glycosylation of lipids and proteins and the synthesis of complex polysaccharides.
Does smooth endoplasmic reticulum contain cisternae
The smooth endoplasmic reticulum is the agranular portion of the organelle and is involved in the synthesis and storage of triglycerols, and phospholipids including cholesterol and fatty acids.
No, the smooth endoplasmic reticulum does not contain cisternae. Instead, they are composed of non-uniformed, disk-like membrane vesicles and elongated tubules. By default, they are free of ribosomes.
The smooth endoplasmic reticulum plays an important role in the synthesis of steroid hormones in the adrenal gland and also contributes to the removal of metabolic wastes. They also play a major role in glycogenolysis and gluconeogenesis in liver cells. Sarcoplasmic reticulum is a modified form of smooth endoplasmic reticulum and is found in skeletal muscle cells (myocytes), the reservoir of calcium ions used for induction of muscle contraction.
As per my conclusion, endoplasmic reticulum is an organelle present inside the cell associated with nuclear pores and the cytosolic face of semi-permeable membrane and constitute of many sections like cisternae, tubules and vesicles. Cisterna are the junction for folding and modifications of protein.