The endoplasmic reticulum can either be smooth or rough, and in general its function is to produce proteins for the rest of the cell to function. The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins. Sometimes, when those proteins are made improperly, the proteins stay within the endoplasmic reticulum. They're retained and the endoplasmic reticulum becomes engorged because it seems to be constipated, in a way, and the proteins don't get out where they're suppose to go. Then there's the smooth endoplasmic reticulum, which doesn't have those ribosomes on it. And that smooth endoplasmic reticulum produces other substances needed by the cell. So the endoplasmic reticulum is an organelle that's really a workhorse in producing proteins and substances needed by the rest of the cell. Show
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Alternate titles: ER, lace-like reticulum By Kara Rogers Table of Contentsendoplasmic reticulum See all media Key People:Ada Yonath Venki Ramakrishnan Thomas Steitz Albert Claude...(Show more)Related Topics:rough endoplasmic reticulum membrane smooth endoplasmic reticulum sarcoplasmic reticulum terminal cisterna...(Show more) See all related content → Top Questions What is the endoplasmic reticulum?
eukaryote Learn more about eukaryotic cells.What is the difference between smooth and rough endoplasmic reticulum?The ER can be classified in two functionally distinct forms: smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER). The morphological distinction between the two is the presence of protein-synthesizing particles, called ribosomes, attached to the outer surface of the RER. The functions of the SER, a meshwork of fine tubular membrane vesicles, vary considerably from cell to cell, one important role being the synthesis of phospholipids and cholesterol, which are major components of the plasma and internal membranes. The RER is generally a series of connected flattened sacs. It plays a central role in the synthesis and export of proteins and glycoproteins and is best studied in secretory cells specializing in these functions. The many secretory cells in the human body include liver cells secreting serum proteins (e.g., albumin), endocrine cells secreting peptide hormones (e.g., insulin), pancreatic acinar cells secreting digestive enzymes, and cartilage cells secreting collagen. What is the function of the endoplasmic reticulum?The endoplasmic reticulum (ER) serves important functions particularly in the synthesis, folding, modification, and transport of proteins. Differences in certain physical and functional characteristics distinguish the two types of ER, known as rough ER (RER) and smooth ER (SER). Ribosomes on RER, which give RER its rough appearance, specialize in the synthesis of proteins that possess a signal sequence that directs them specifically to the ER for processing. Proteins synthesized by the RER have specific final destinations, such as the cell membrane, cell exterior, or the ER itself. SER is involved in the synthesis of lipids, including cholesterol and phospholipids, which are used in the production of new cellular membrane. In cells of the liver, SER contributes to the detoxification of drugs and harmful chemicals. The sarcoplasmic reticulum is a specialized type of SER that regulates calcium ion concentration in the cytoplasm of striated muscle cells. ribosome Learn more about ribosomes.When was the endoplasmic reticulum discovered?The ER was first noted in the late 19th century, when studies of stained cells indicated the presence of some type of extensive cytoplasmic structure, then known as the gastroplasm. The electron microscope made possible the study of the morphology of the ER in the 1940s, when it was given its present name. electron microscope Learn more about the electron microscope.Summary Read a brief summary of this topicendoplasmic reticulum (ER), in biology, a continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells and serves multiple functions, being important particularly in the synthesis, folding, modification, and transport of proteins . All eukaryotic cells contain an endoplasmic reticulum (ER). In animal cells, the ER usually constitutes more than half of the membranous content of the cell. Differences in certain physical and functional characteristics distinguish the two types of ER, known as rough ER and smooth ER. Rough ER is named for its rough appearance, which is due to the ribosomes attached to its outer (cytoplasmic) surface. Rough ER lies immediately adjacent to the cell nucleus, and its membrane is continuous with the outer membrane of the nuclear envelope. The ribosomes on rough ER specialize in the synthesis of proteins that possess a signal sequence that directs them specifically to the ER for processing. (A number of other proteins in a cell, including those destined for the nucleus and mitochondria, are targeted for synthesis on free ribosomes, or those not attached to the ER membrane; see the article ribosome.) Proteins synthesized by the rough ER have specific final destinations. Some proteins, for example, remain within the ER, whereas others are sent to the Golgi apparatus, which lies next to the ER. Proteins secreted from the Golgi apparatus are directed to lysosomes or to the cell membrane; still others are destined for secretion to the cell exterior. Proteins targeted for transport to the Golgi apparatus are transferred from ribosomes on rough ER into the rough ER lumen, which serves as the site of protein folding, modification, and assembly. More From Britannica The proximity of the rough ER to the cell nucleus gives the ER unique control over protein processing. The rough ER is able to rapidly send signals to the nucleus when problems in protein synthesis and folding occur and thereby influences the overall rate of protein translation. When misfolded or unfolded proteins accumulate in the ER lumen, a signaling mechanism known as the unfolded protein response (UPR) is activated. The response is adaptive, such that UPR activation triggers reductions in protein synthesis and enhancements in ER protein-folding capacity and ER-associated protein degradation. If the adaptive response fails, cells are directed to undergo apoptosis (programmed cell death). Study the interdependence of a cell's nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus See all videos for this articleSmooth ER, by contrast, is not associated with ribosomes, and its functions differ. The smooth ER is involved in the synthesis of lipids, including cholesterol and phospholipids, which are used in the production of new cellular membrane. In certain cell types, smooth ER plays an important role in the synthesis of steroid hormones from cholesterol. In cells of the liver, it contributes to the detoxification of drugs and harmful chemicals. The sarcoplasmic reticulum is a specialized type of smooth ER that regulates the calcium ion concentration in the cytoplasm of striated muscle cells. The highly convoluted and labyrinthine structure of the ER led to its description in 1945 as a “lace-like reticulum” by cell biologists Keith Porter, Albert Claude, and Ernest Fullman, who produced the first electron micrograph of a cell. In the late 1940s and early 1950s, Porter and colleagues Helen P. Thompson and Frances Kallman introduced the term endoplasmic reticulum to describe the organelle. Porter later worked with Romanian-born American cell biologist George E. Palade to elucidate key characteristics of the ER. Which of the following is a function of endoplasmic reticulum?The endoplasmic reticulum (ER) is a large, dynamic structure that serves many roles in the cell including calcium storage, protein synthesis and lipid metabolism. The diverse functions of the ER are performed by distinct domains; consisting of tubules, sheets and the nuclear envelope.
Which is not a part of endoplasmic reticulum?Reason: Mitochondria, chloroplast and peroxisomes are not the part of endomembrane system because their function are not coordinated with the same.
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Which of the following is not the function of endoplasmic reticulum?
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