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The little workhouses inside the cell are called cell organelles. Each cell is generally responsible for all of life’s operations. By breaching the plasma membrane, homogenising the mixture, and ultracentrifugating it, organelles can be freed. Organelles vary in size and density, and they settle out at varied speeds. The endoplasmic reticulum (ER) is represented by a network of membranes that surrounds a single continuous area. As it is basically stated previously, that granular endoplasmic reticulum is linked to ribosomes (giving the exterior surface a rough, or granular appearance). Rough ER is mainly another name for granular endoplasmic reticulum. The granular ER is generally involved in Golgi apparatus protein packaging. The agranular, or smooth, ER is the exact location of lipid production and it also lacks ribosomes. Agranular ER also accumulates and releases calcium ions (Ca2+).
Structure of Endoplasmic Reticulum
In plant and animal cells, the endoplasmic reticulum is a network of tubules and flattened sacs that perform a number of activities. The structure and function of the two ER regions differ. Ribosomes are connected to the cytoplasmic side of the rough ER membrane. Smooth ER does not have connected ribosomes. The smooth ER is often a tubule network, whereas the rough ER is a series of flattened sacs. The lumen is the inside space of the ER. The ER is a large structure that extends from the cell membrane through the cytoplasm and connects to the nuclear envelope. The ER lumen and the space inside the nuclear envelope are in the same compartment because the ER is connected to the nuclear envelope.
Role of Endoplasmic Reticulum
The endoplasmic reticulum performs a variety of activities, including folding protein molecules in cisternae and transporting produced proteins to the Golgi apparatus in vesicles. Protein synthesis is also carried out by the rough endoplasmic reticulum. Protein disulfide isomerase (PDI), Erp29, the calnexin, calreticulin, and the peptidylprolyl isomerase family are all endoplasmic reticulum chaperone proteins that help new proteins fold correctly.
Only properly folded proteins are transferred from the rough ER to the Golgi apparatus; unfolded proteins trigger an ER stress response called the unfolded protein response. Endoplasmic reticulum stress response (ER stress) is a state in which protein folding slows, resulting in an increase in unfolded proteins. It can be caused by disturbances in redox regulation, glucose deprivation, calcium regulation and viral infection or over-expression of proteins. This stress is being investigated as a possible cause of harm in hypoxia/ischemia, insulin resistance, and other conditions.
Location of Endoplasmic Reticulum
Most of the instructions from the nucleus are processed by the endoplasmic reticulum. As a result, the nucleus is found surrounded by the endoplasmic reticulum, that spreads outward. The endoplasmic reticulum can make up more than half of the cell in cells that release a lot of stuff for the rest of the body.
The nucleus, mainly, produces mRNA (i.e messenger RNA), that helps in instructing the cell on how to construct proteins. Many ribosomes are found in the rough endoplasmic reticulum, which is where protein is produced. This region of the organelle produces proteins and begins to fold them into proper shape. Lipid production takes place mostly in the smooth endoplasmic reticulum. As a result of which it is found to be devoid of ribosomes. Rather, it initiates a series of events that produce the phospholipid molecules required for the formation of different membranes and organelles. The rough endoplasmic reticulum is frequently closer to the nucleus, while the smooth endoplasmic reticulum is much further away. Both forms, on the other hand, are linked to the nucleus by a series of tiny tubules.
Types of Endoplasmic Reticulum
Within each cell, there are two forms of ER: smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER) (RER). Each has distinct functions and, in many cases, morphologies. The SER is involved in lipid metabolism and serves as the cell’s calcium reserve. This is especially true in muscle cells that require Ca2+ ions to contract. The SER is also implicated in phospholipid and cholesterol production. It is frequently found on the cell’s outskirts. The RER, on the other side, is frequently detected near to the nucleus. It has membrane-bound ribosomes, which give it its distinctive ‘rough’ appearance.
These ribosomes produce proteins that are intended for the ER lumen and are transported into the organelle when they are translated. These proteins are translated in the cytoplasm and have a brief signal produced with a couple amino acids in their N-terminus. Special proteins connect to the developing polypeptide chain and transfer the complete ribosome and associated translation machinery to the ER as soon as the signal is translated. These polypeptides might either be RER resident proteins or be transported to the Golgi network to be processed and secreted.
Conclusion
Most eukaryotic animal and plant cells have an endoplasmic reticulum organelle. Rough ER and smooth ER are two interrelated sub-compartments that emerge frequently. Both types are made up of flattened tubes joined by a membrane. The rough ER is involved in the manufacture, folding, quality checking, and despatch of certain proteins, with millions of membrane bound ribosomes. Smooth ER is closely linked to lipid (fat) production and metabolism, as well as steroid hormone production. It will have a detoxifying effect.
