Endoplasmic Reticulum – Structure, Types and Functions
All living organisms have cells as their basic structural and functional unit. Antonie Van Leeuwenhoek was the first to see and describe a living cell. Some organisms are composed of a single cell and are referred to as unicellular organisms, whereas others are composed of many cells and are referred to as multicellular organisms. All organisms are made up of cells.
- The endoplasmic Reticulum Structure is a network of membranes that are distributed throughout the cell and connect to the nucleus.
- The membranes differ slightly from cell to cell, and the size and shape of the ER are determined by a cell’s activity. The Endoplasmic reticulum (ER) is a vital organelle in the cell.
- Whereas the nucleus serves as the cell’s brain, the ER functions as a manufacturing and packaging system. The Golgi apparatus, ribosomes, mRNA, and tRNA all collaborate with the ER.
- Prokaryotes and red blood cells, for example, lack any kind of ER. Cells that synthesize and release a lot of proteins will need a lot of ER.
- The endoplasmic reticulum gets its name from the fact that it looks like a “net in the cytoplasm” under a light microscope.
- Some ER membranes remain connected to the plasma membrane and the nuclear envelope.
- ER can be either rough or smooth. Rough ER has attached ribosomes on its outer surface, whereas smooth ER does not have attached ribosomes.
- The endoplasmic reticulum serves as the cell’s secretory, storage, circulatory, and nervous systems. It is also the site of cellular membrane biogenesis.
- Endoplasmic reticulum membranes have been found to contain a wide range of enzymes required for a variety of important synthetic activities.
- The endoplasmic reticulum membrane is 50 to 60 A° thick and fluid-mosaic, similar to the plasma membrane unit membrane.
- The endoplasmic reticulum membrane is continuous with the plasma membrane, nuclear membrane, and Golgi apparatus membranes.
- Stearases, NADH-cytochrome C reductase, NADH diaphorase, glucose-6-phosphatase, and Mg++ activated ATPase are the most important enzymes.
- The endoplasmic reticulum cavity is well developed and serves as a passage for secretory products.
- The endoplasmic reticulum can take three different forms:
- The vesicles are oval membrane-bound vacuolar structures with diameters ranging from 25 to 500 nm.
- They are found in most cells but are especially abundant in the SER, where they frequently remain isolated in the cytoplasm.
- RER is typically found as cisternae in cells with synthetic functions, such as those found in the pancreas, notochord, and brain.
- They continue to be arranged in parallel bundles or stakes.
- The cisternae are unbranched, long, flattened tubules with a diameter of 40 to 50 nm.
- Tubular ER is frequently found in SER and is dynamic in nature, i.e., it is associated with membrane movements, fission, and fusion between cytocavity network membranes.
- They typically range in size from 50 to 190 nm and can be found in almost all cells.
- Tubules are branched structures that, along with cisternae and vesicles, comprise the reticular system.
Types of Endoplasmic Reticulum
Rough Endoplasmic Reticulum
- Rough ER (RER) is also included in the ribosomes section and plays an important role in protein synthesis and packaging.
- The protein synthesis process begins when mRNA travels from the nucleus to a ribosome on the RER’s surface.
- Ribosomes bind to the ER membrane, making it “rough.” The RER is also connected to the nuclear envelope that surrounds the nucleus.
- Because of the direct relationship between the perinuclear space and the ER lumen, molecules can pass through both membranes.
- As the ribosome constructs the amino acid chain, it is forced into the RER’s cisternal space. When protein production is finished and the proteins have been collected, the RER pinches off a vesicle.
- Some proteins are used within the cell, while others are released into the intercellular space.
- The vesicle, which is a small membrane bubble, can travel into the cell membrane or the Golgi apparatus.
Endoplasmic Reticulum Smooth
- Because the ribosomes are not attached to the membranes of this type of endoplasmic reticulum, its walls are smooth.
- The smooth endoplasmic reticulum is found primarily in cells involved in the metabolism of lipids (including steroids) and glycogen.
- Adipose cells, interstitial cells, glycogen-storing cells of the liver, heart conduction fibers, spermatocytes, and leucocytes are examples.
- It is primarily in charge of transporting proteins and other carbohydrates to other organs, such as lysosomes, the Golgi apparatus, the plasma membrane, and so on.
- They also provide increased surface area for cellular reactions.
- They play an important role in the formation of the skeletal structure.
- Proteins, lipids, glycogen, and other steroid hormones such as cholesterol, progesterone, and testosterone require them for synthesis.
- They aid in the formation of nuclear membranes during cell division.
- The ER performs a variety of functions, including material transport between different parts of the cell.
- It eliminates waste and cleanses the cells. They also degrade worn-out cell components.
- by digesting foreign or undesirable materials andonar
- The membrane-bound sacs contain digestive enzymes that break down foreign material that enters the cell.
Frequently Asked Questions
Question 1: Explain the structure of the smooth endoplasmic reticulum.
- It is a network of flattened sacs with several ribosomes on the outside, hence the name.
- Rough ER is abundant in cells where protein synthesis occurs (such as hepatocytes)
- It is responsible for the synthesis and secretion of proteins in the liver, as well as hormones and other substances in the glands.
Question 2: Mention some functions of the endoplasmic reticulum.
- It is in charge of carbohydrates metabolism.
- It is also in charge of producing essential lipids like phospholipids and cholesterol.
- The ER secretes calcium ions, which are required by the nervous and muscular systems.
Question 3: Define the endoplasmic reticulum.
The Endoplasmic Reticulum is a complex network of tubular membranes found only in the cytoplasm of eukaryotic cells. The endoplasmic reticulum is a reticulum or network of tiny tubular structures scattered throughout the cytoplasm.
Question 4: Mention the functions of the rough endoplasmic reticulum.
- The majority of rough ER functions are related to protein synthesis.
- Protein sorting is the third most important function after protein synthesis and protein folding.
- The rough endoplasmic reticulum is also important in protein folding.
Question 5: Mention the functions of the smooth endoplasmic reticulum.
- The smooth ER is in charge of the synthesis of essential lipids like phospholipids and cholesterol.
- It is also in charge of carbohydrate metabolism. These are essential for the nervous and muscular systems.
- Smooth ER is also in charge of steroid hormone production and secretion.