39. 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.
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 endoplasmic reticulum. Be sure to identify the correct order in which the proteins move through each of these structures.
My answer:
Proteins are produced by ribosomes on the rough part of the endoplasmic reticulum. These proteins are then packed into vesicles. Next, the proteins are moved from the rough ER to the Golgi apparatus by means of vesicles. Processing of the proteins takes place in the Golgi apparatus, after which they are packaged into new vesicles. Some vesicles then release their proteins outside the cell. Remaining vesicles stay inside the cell and become lysosomes.
Is this OK?
Thanks
-MC
Your answer is mostly correct but there are a few details that can be added for a more complete explanation.
Proteins are indeed manufactured from the "blueprints" found on DNA. This process, called protein synthesis, begins in the nucleus of the cell where the DNA is transcribed into a single-stranded molecule called RNA. This RNA molecule then exits the nucleus and attaches to ribosomes.
Ribosomes are the protein-producing factories of the cell. They can be found both free-floating in the cytoplasm and attached to the rough endoplasmic reticulum (ER). When ribosomes are attached to the rough ER, they produce proteins that are destined to be distributed throughout the rest of the cell or exported out of the cell.
After the proteins are synthesized by ribosomes, they are moved into the lumen (internal space) of the rough endoplasmic reticulum. The ER plays a crucial role in protein folding and quality control. Within the ER, proteins undergo various modifications that help them attain their functional form, such as the addition of sugar molecules (glycosylation) or the formation of disulfide bonds.
From the rough ER, the proteins are packaged into vesicles. Vesicles are small membrane-bound sacs that bud off from one compartment of the cell and transport their cargo to another compartment. In this case, the vesicles carrying the newly synthesized proteins bud off from the rough ER and move towards the Golgi apparatus.
The Golgi apparatus is the next destination for the vesicles carrying the proteins. It consists of a series of flattened membrane sacs called cisternae. The Golgi apparatus further modifies, sorts, and packages the proteins received from the rough ER. It adds various tags, such as signal sequences or specific sugar molecules, to direct the proteins to their final destinations within the cell or outside of the cell.
Once the proteins have been processed and modified within the Golgi apparatus, they are packaged into new vesicles called secretory vesicles or transport vesicles. Some of these vesicles are then transported to the cell membrane where they fuse with it, releasing the proteins outside of the cell through a process called exocytosis. This allows the proteins to be used by other cells or to carry out their functions in extracellular environments.
Other vesicles produced by the Golgi apparatus stay inside the cell and become lysosomes. Lysosomes contain specialized enzymes that break down various cellular components or foreign materials, such as bacteria or damaged organelles.
So, in summary, the correct order of movement for the proteins through each of these structures is: ribosomes -> rough endoplasmic reticulum -> vesicles -> Golgi apparatus -> secretory vesicles/lysosomes.