5.5B: The Endoplasmic Reticulum
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- Ying Liu
- City College of San Francisco
Briefly describe rough endoplasmic reticulum and state its functions.
Briefly describe smooth endoplasmic reticulum and state its functions.
The endoplasmic reticulum or ER is a maze of parallel membranous tubules and flattened sacs surrounding the nucleus that connects with the nuclear membrane and runs throughout the cytoplasm (Figure \(\PageIndex{33}\)). The ER functions to:
- provide a surface area for protein and lipid synthesis;
- form a pathway for transporting molecules within the cell; and
- provide a storage area for molecules the cell has synthesized.
The endoplasmic reticulum connects to the pores of the nuclear envelope. The pores in the nuclear membrane allow ribosomal subunits and mRNA transcribed off genes in the DNA to leave the nucleus, enter the cytoplasm, and participate in protein synthesis. There are two distinct regions of the ER: the rough ER and the smooth ER.
| Concept map for Eukaryotic Cell Structure |
Summary
- The endoplasmic reticulum or ER is a maze of parallel membranous tubules and flattened sacs surrounding the nucleus that connects with the nuclear membrane and runs throughout the cytoplasm.
- ER with ribosomes attached is called rough endoplasmic reticulum and is involved in protein synthesis, production of new membrane, modification of newly formed proteins, and transport of these proteins and membrane to other locations within the cell.
- ER without ribosomes is called smooth endoplasmic reticulum and contains enzymes for lipid biosynthesis, especially the synthesis of phospholipids and steroids. The smooth endoplasmic reticulum forms transition vesicles to transfer molecules produced in the rough ER to the Golgi complex.
Questions
Study the material in this section and then write out the answers to these questions. Do not just click on the answers and write them out. This will not test your understanding of this tutorial.
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_____ Coated with ribosomes.
(ans)
_____ Formstransition vesicles to transfer molecules produced in the rough ER to the Golgi apparatus and other parts of the cell. (ans)
- smooth endoplasmic reticulum
- rough endoplasmic reticulum