Proteins are manufactured from the "blueprints" found on DNA. After they are translated, they are moved through a system of internal membranes before being distributed throughout the rest of the cell. At some point in this process, they are modified to their functional form.
• Describe the movement of proteins from their manufacturing point through this internal membrane system.
• In your own words, discuss the role of each of the following structures in the whole process: cell membrane, vesicles (at two points in the process), ribosomes, Golgi apparatus, and endoplasmc reticulum. Be sure to identify the correct order in which the proteins move through each of these structures.
-If any one knows anything that could help me answer this question. Any help is appreciated.
The movement of proteins from their manufacturing point through the internal membrane system can be described in the following steps:
1. Protein synthesis: Proteins are manufactured from the "blueprints" found on DNA in a process called translation. This occurs in the cytoplasm of the cell, where ribosomes (small structures made of RNA) read the genetic information and assemble the proteins.
2. Endoplasmic reticulum (ER): After synthesis, the proteins are moved into the endoplasmic reticulum, a network of membrane-bound sacs and tubules within the cell. The proteins enter the ER through the ribosomes attached to its surface. This region is called the rough ER.
3. Rough ER: The proteins are further modified and folded into their initial, functional form within the rough ER. This compartment helps in protein folding and quality control.
4. Golgi apparatus: From the rough ER, the proteins are packaged into vesicles (small membrane-bound sacs) and transported to the Golgi apparatus. The Golgi is another membrane-bound organelle consisting of a stack of flattened sacs called cisternae.
5. Vesicles (1st point): The proteins are transported to the Golgi apparatus by vesicles formed from the rough ER. These vesicles fuse with the Golgi and release their protein cargo into the Golgi apparatus.
6. Golgi apparatus processing: Within the Golgi apparatus, the proteins undergo further modifications such as glycosylation (attachment of sugar molecules) and sorting. The Golgi modifies, sorts, and packages the proteins for further transport.
7. Vesicles (2nd point): From the Golgi apparatus, proteins are packaged into new vesicles, which bud off from the Golgi stacks. These vesicles contain the fully processed and sorted proteins.
8. Cell membrane: The vesicles containing the proteins are transported to the cell membrane, where they fuse with the membrane and release their cargo outside the cell (exocytosis). This allows the proteins to be distributed throughout the rest of the cell or secreted outside the cell to perform their specific functions.
In summary, proteins are synthesized in the cytoplasm by ribosomes, moved into the rough ER for initial modification, transported to the Golgi apparatus for further processing and sorting via vesicles, and then transported to the cell membrane for release or distribution.
To understand the movement of proteins through the internal membrane system, let's break it down step-by-step:
1. Protein Synthesis: Proteins are manufactured from the blueprints encoded in DNA in a process called protein synthesis. This occurs in the cell's nucleus, where DNA is transcribed into mRNA. The mRNA molecule then carries the genetic information to the cytoplasm, where it binds to a ribosome.
2. Ribosomes: Ribosomes are the cellular structures responsible for protein synthesis. They serve as the site where the mRNA is translated into a specific sequence of amino acids, forming a polypeptide chain.
3. Endoplasmic Reticulum (ER): After the protein is synthesized by the ribosome, it moves to the endoplasmic reticulum (ER), which is a network of membranes connected to the nuclear envelope. There are two types of ER: rough ER (RER), which has ribosomes attached to its surface, and smooth ER (SER), which lacks ribosomes.
4. Rough Endoplasmic Reticulum (RER): The ribosomes attached to the RER synthesize proteins that are destined to be either secreted or become integral components of the cell's membranes. As the protein is synthesized, it enters the ER lumen (the space within the ER membrane) and is translocated through the ER membrane.
5. Vesicles: Once the protein is translocated into the ER lumen, it undergoes modifications such as folding, glycosylation (addition of sugar molecules), and disulfide bond formation to attain its functional form. These modified proteins are then loaded into vesicles, which are small, membrane-bound sacs that bud off from the ER.
6. Golgi Apparatus: The vesicles containing the proteins are transported from the ER to the Golgi apparatus, which is a stacked series of membranous sacs called cisternae. The Golgi apparatus further modifies, sorts, and packages the proteins into different vesicles for their specific destinations.
7. Vesicles (again): After the Golgi apparatus modifies the proteins, they are once again packaged into vesicles. Now, these vesicles can have different functions and destinations depending on the modified proteins. Some vesicles will transport the proteins to the cell membrane for secretion, while others will carry the proteins to specific organelles or compartments within the cell.
8. Cell Membrane: The vesicles, containing the modified proteins, fuse with the cell membrane, releasing their cargo outside the cell or embedding it within the cell membrane. This allows the proteins to be distributed throughout the rest of the cell or used for secretion to the outside environment.
In summary, the proteins move from their manufacturing site in the ribosomes to the rough endoplasmic reticulum (RER), where they are translocated into the ER lumen. Then, the proteins are packaged into vesicles and transported to the Golgi apparatus, where they undergo further modifications and are sorted into new vesicles. Finally, these vesicles fuse with the cell membrane, releasing the proteins to their designated destinations.