1. Nucleus:
* Role: Contains the genetic material (DNA) that codes for proteins.
* Process: DNA is transcribed into messenger RNA (mRNA) within the nucleus.
2. Ribosomes:
* Role: Site of protein synthesis.
* Process: Ribosomes read the mRNA code and assemble amino acids into polypeptide chains.
* Location: Found free-floating in the cytoplasm or attached to the endoplasmic reticulum (ER).
3. Endoplasmic Reticulum (ER):
* Role: A network of interconnected membranes that serves as a transport system and processing center for proteins.
* Process:
* Rough ER: Ribosomes are attached to the surface. Proteins synthesized on these ribosomes are transported into the ER lumen (the space within the ER) where they are folded and modified.
* Smooth ER: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage.
4. Golgi Apparatus:
* Role: Further modifies, sorts, and packages proteins for export.
* Process:
* Proteins move from the ER to the Golgi apparatus in transport vesicles.
* The Golgi adds carbohydrates to proteins (glycosylation) and sorts them into different types of vesicles.
5. Transport Vesicles:
* Role: Membrane-bound sacs that transport proteins between organelles.
* Process:
* Bud off from the ER and Golgi.
* Fuse with other organelles (like the Golgi) or with the plasma membrane for protein export.
6. Plasma Membrane:
* Role: The outer boundary of the cell; responsible for exporting proteins outside the cell.
* Process:
* Transport vesicles fuse with the plasma membrane, releasing their protein cargo into the extracellular space.
In summary:
* DNA in the nucleus provides the code for protein synthesis.
* Ribosomes translate the code into proteins.
* The ER processes and modifies proteins.
* The Golgi apparatus further modifies, sorts, and packages proteins.
* Transport vesicles move proteins between organelles.
* The plasma membrane releases proteins outside the cell.
