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Life Science: Part 1
What happens to all the products that are built on the assembly line of a factory? The final touches are put on them in the finishing and packing department.
Workers in this part of the plant are responsible for making minor adjustments to the finished products. They inspect the products for flaws, clean them of any extra material added during their manufacture, wrap them, and target them for packing. The Golgi apparatus performs all these tasks in the cell.
Golgi Apparatus Structure
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| The Golgi apparatus receives ER proteins and modifies them prior to shipping. |
After leaving the production site of the ER, most products are transported to the Golgi apparatus. The GOLGI APPARATUS consists of several flattened saclike membranes. These sacs sit one on top of the other like a stack of pancakes, and all of the sacs are interconnected. The smooth ER manufactures the Golgi apparatus by pinching off parts of itself. These bits of membrane add themselves to the Golgi apparatus.
Golgi Apparatus Function
The Golgi apparatus is analogous to the finishing and packing room in a factory. Once the ribosome finishes manufacturing a protein in the rough ER, the protein needs to be prepared for use or export. Special enzymes will trim off any extra amino acids, and then the unfinished protein moves through channels in the smooth ER.
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| Animation of exocytosis |
Eventually, some of the smooth ER membrane is pinched off as a SPHERICAL VESICLE. The proteins are either contained inside these structures or are carried on their surfaces. These vesicles are absorbed by the Golgi apparatus, and proteins are processed as they pass from one sac to the next. As the proteins move they are processed. When the protein is ready for export, it is pinched off of the Golgi and released into the cytoplasm.
What becomes of the final product of protein synthesis once it enters the cytoplasm? Some of these proteins eventually become membrane proteins and help with the functions of transport or self-recognition. These proteins are carried on the outside of the spherical vesicles and transported to the plasma membrane. Some of these proteins are retained within the cytoplasm for use by the cell.
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| Proteins are received by the cis face of the Golgi and exit through the trans face after modification. |
All of this production leaves behind quite a mess! Who cleans up the trash?
