• The ER enables the movement of materials from one area of the cell to another, constituting the circulatory system of the cell.
  • Desmotubule formation: Desmotubules are tubular extensions that stretch through plasmodesmata to connect the ER in two adjacent plant cells.
  • Support – The cytoskeleton, which also helps to preserve the cell’s shape, uses the ER as an intracellular supporting framework.
  • Localization of Organelles – It maintains correct distribution and stationing of the cell organelles in relation to one another.
  • Surface for Synthesis: The ER provides a large surface area for a variety of material synthesis.

Functions of Smooth endoplasmic reticulum

  1. The SER offers a surface for the synthesis of fatty acids, phospholipids, glycolipids, steroids, and colours for the eyes.
  2. Glycogen Metabolism: The SER transports enzymes for the liver cells’ glycogen metabolism. In liver cells, glycogen granules are more heavily concentrated on the SER membrane’s exterior.
  3. Detoxification – The SER contains enzymes that help the liver detoxify substances like pesticides and carcinogens into harmless forms that can be excreted by cells.
  4. Production of organelles: The SER creates vacuoles, microbodies, lysosomes, and Golgi apparatus.
  5. The proteins move from the RER through the SER to the Golgi apparatus for additional processing.
  6. Skeletal Muscle Contraction – Sarcoplasmic reticulum releases Ca2+ ions to generate contraction and absorbs Ca2+ ions to cause relaxation in skeletal muscle cells.
  7. Fat Oxidation: The early reactions in the oxidation of lipids are carried out by the SER membranes.

Functions of Rough Endoplasmic Reticulum

  1. Surface for Ribosomes—The RER offers a sizable surface for ribosome attachment.
  2. Surface for synthesis. The RER provides a sizable surface on which ribosomes can easily carry out protein synthesis. The newly produced proteins may pass into the ER lumen or enter the ER membranes, joining the membrane structure. The proteins that eventually become a part of the ER membrane go from the ER through the membranes of other cell organelles, such as the Golgi apparatus and secretary vesicles, to become the permanent proteins of the plasma membrane. For export, the proteins that enter the ER lumen are packaged.
  3. Packaging: The proteins in the ER lumen are broken down and packaged into sphere-shaped membrane-bound vesicles that are then detached from the ER. Different things happen to these vesicles. Some act as storage vesicles and stay in the cytoplasm, whereas others go to the plasma membrane and exocytose their contents. Some combine with the Golgi apparatus to further process their proteins for cellular storage or release.
  4. Smooth ER Formation—By losing ribosomes, the RER gives rise to the smooth ER.
  5. Creation of the Nuclear Envelope During cell division, the RER creates the nuclear envelope around the daughter cells.
  6. Formation of Glycoproteins – The RER is where the process of joining carbohydrates and proteins to produce glycoproteins begins and ends.


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