How are the functions of ribosomes, Golgi bodies, and the endoplasmic reticulum related
Quick look Show Rough ER (RER) is involved in some protein production, protein folding, quality control and despatch. It is called ‘rough’ because it is studded with ribosomes Smooth E R (SER) is associated with the production and metabolism of fats and steroid hormones. It is ‘smooth’ because it is not studded with ribosomes and is associated with smooth slippery fats. To view a micrograph of ER interpreted using the Gridpoint cross-hairs device, click here. CELLS NEED THE ROUGH AND THE SMOOTH Think of a cell as a “multitude of membranes” we said in an earlier section. This statement certainly applies to the endoplasmic reticulum an organelle found in eukaryotic cells.
There are two types of endoplasmic reticulum: rough endoplasmic reticulum (rough ER) and smooth endoplasmic reticulum (smooth ER). Both types are present in plant and animal cells. The two types of ER often appear as if separate, but they are sub-compartments of the same organelle. Cells specialising in the production of proteins will tend to have a larger amount of rough ER whilst cells producing lipids (fats) and steroid hormones will have a greater amount of smooth ER. Part of the ER is contiguous with the nuclear envelope. The Golgi apparatus is also closely associated with the ER and recent observations suggest that parts of the two organelles, i.e. the ER and the Golgi complex, are so close that some chemical products probably pass directly between them instead of being packaged into vesicles (droplets enclosed within a membrane) and transported to them through the cytoplasm ROUGH ENDOPLASMIC RETICULUM This is an extensive organelle composed of greatly convoluted but flattish sealed sacs, which are contiguous with the nuclear membrane. It is called ‘rough’ endoplasmic reticulum because it is studded on its outer surface (the surface in contact with the cytosol) with ribosomes. These are called membrane bound ribosomes and are firmly attached to the outer cytosolic side of the ER About 13 million ribosomes are present on the RER in the average liver cell. Rough ER is found throughout the cell but the density is higher near the nucleus and the Golgi apparatus. Ribosomes on the rough endoplasmic reticulum are called ‘membrane bound’ and are responsible for the assembly of many proteins. This process is called translation. Certain cells of the pancreas and digestive tract produce a high volume of protein as enzymes. Many of the proteins are produced in quantity in the cells of the pancreas and the digestive tract and function as digestive enzymes. The rough ER working with membrane bound ribosomes takes polypeptides and amino acids from the cytosol and continues protein assembly including, at an early stage, recognising a ‘destination label’ attached to each of them. Proteins are produced for the plasma membrane, Golgi apparatus, secretory vesicles, plant vacuoles, lysosomes, endosomes and the endoplasmic reticulum itself. Some of the proteins are delivered into the lumen or space inside the ER whilst others are processed within the ER membrane itself. In the lumen some proteins have sugar groups added to them to form glycoproteins. Some have metal groups added to them. It is in the rough ER for example that four polypeptide chains are brought together to form haemoglobin. Protein folding unit Protein quality control section Rigorous quality control plays a part in cystic fibrosis From Rough ER to Golgi SMOOTH ENDOPLASMIC RETICULUM Smooth ER is more tubular than rough ER and forms an interconnecting network sub-compartment of ER. It is found fairly evenly distributed throughout the cytoplasm. Smooth ER – the detox stop The contraction of muscle cells is triggered by the orderly release of calcium ions. These ions are released from the smooth endoplasmic reticulum. SUMMARY
Amended 19.11.15 DA. How is the endoplasmic reticulum related to Golgi bodies in terms of function?The Golgi apparatus distributes the many proteins and lipids that it receives from the ER and then modifies the plasma membrane, lysosomes, and secretory vesicles.
How are ribosomes and endoplasmic reticulum related?The ribosome that is synthesizing the protein is directly attached to the ER membrane. These membrane-bound ribosomes coat the surface of the ER, creating regions termed rough endoplasmic reticulum, or rough ER (Figure 12-36A).
What is the role of ribosomes and Golgi body?The major function of ribosomes is the production of proteins and that of the Golgi apparatus is the modification and packaging of those proteins. They are usually present in high number in cells that secrete digestive enzymes as they are responsible for the production of those enzymes.
How do endoplasmic reticulum ER and Golgi work together to make and release proteins?Protein cargo moves from the ER to the Golgi, is modified within the Golgi, and is then sent to various destinations in the cell, including the lysosomes and the cell surface. The Golgi processes proteins made by the endoplasmic reticulum (ER) before sending them out to the cell.
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