Learning Objectives Describe the structure of the endoplasmic reticulum and its role in synthesis and metabolism. The proteins made by the rough endoplasmic reticulum are for use outside of the cell. Functions of the smooth endoplasmic reticulum include synthesis of carbohydrates, lipids, and steroid hormones; detoxification of medications and poisons; and storage of calcium ions. Key Terms lumen : The cavity or channel within a tube or tubular organ. The Endoplasmic Reticulum The endoplasmic reticulum ER is a series of interconnected membranous sacs and tubules that collectively modifies proteins and synthesizes lipids.
Rough ER The rough endoplasmic reticulum RER is so named because the ribosomes attached to its cytoplasmic surface give it a studded appearance when viewed through an electron microscope. Protein synthesis and folding One of the major functions of the ER is to serve as a site for protein synthesis for secreted and integral membrane proteins [ 8 ], as well as a subpopulation of cytosolic proteins [ 1 ]. Lipid biogenesis While the ER is a major site of protein synthesis, it is also a site of bulk membrane lipid biogenesis [ 4 ], which occurs in the endomembrane compartment that includes the ER and Golgi apparatus.
Regulation of ER shape and function The ER is a complex organelle, involved in protein and lipid synthesis, calcium regulation and interactions with other organelles. Open in a separate window. ER structure There have been several excellent, recent reviews that cover the topic of general ER structure in detail [ 7 , 44 — 48 ], so we will limit our review of the basic ER structure to only those factors that may play a role in changing the shape of ER in response to signaling.
ER shaping proteins ER tubules Peripheral ER structures are just as distinct and diverse as the set of proteins that contribute to their shape. ER sheets We have considered how tubules are formed and maintained, which leads the discussion to sheets, the other peripheral ER structure.
ER microtubule interactions It is clear that proteins involved in the promotion, maintenance or stabilization of peripheral ER structures function through interactions with additional proteins or structures, and these interactions are key to proper formation of the ER network. Changes in ER structure during mitosis During mitosis many cellular structures are dramatically remodeled to facilitate chromosome segregation. Changes in ER during oocyte maturation and fertilization One of the greatest changes during development occurs at fertilization.
ER changes in response to ER stress As seen so far, the ER is an organelle of many different functions that must be tightly regulated to carry out the proper functions. Closing remarks The ER is a complex organelle that plays a pivotal role in protein and lipid synthesis, calcium storage and stress response. References 1. Diversity and selectivity in mRNA translation on the endoplasmic reticulum.
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Phosphoregulation of STIM1 leads to exclusion of the endoplasmic reticulum from the mitotic spindle. 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. Endoplasmic Reticulum Smooth. William Gahl, M. Featured Content.
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