Golgi Processing and Transport quiz #1 Flashcards
Golgi Processing and Transport quiz #1
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What are the main functions of the Golgi apparatus in protein processing and transport within the cell?
The Golgi apparatus modifies proteins (mainly through glycosylation), sorts them, and directs their transport to various destinations. It acts as a hub for both anterograde (ER to plasma membrane) and retrograde (plasma membrane to ER) transport, ensuring proteins are properly processed and sent to the correct location. Describe the structural organization of the Golgi apparatus and the significance of its different regions.
The Golgi apparatus is composed of flattened membrane-bound stacks called cisternae, organized into cis (facing the ER), medial (middle), and trans (facing the plasma membrane) regions. Each region is responsible for specific protein modifications and sorting functions. How do proteins move through the Golgi apparatus, and what are the two main models explaining this movement?
Proteins move through the Golgi via a combination of the vesicular transport model (proteins move in vesicles between stationary cisternae) and the cisternae maturation model (cisternae themselves move and mature from cis to trans). Current evidence suggests both models operate together. What is glycosylation, and what types occur in the Golgi apparatus?
Glycosylation is the addition of carbohydrate groups to proteins. In the Golgi, both N-linked (sugar attached to a nitrogen atom) and O-linked (sugar attached to a hydroxyl group) glycosylation occur, with terminal glycosylation being the final modification before proteins leave the Golgi. What happens to misfolded proteins in the ER, and how does the cell ensure only properly folded proteins reach the Golgi?
Misfolded proteins in the ER are recognized by chaperone proteins and targeted for degradation by the proteasome. Only properly folded proteins, marked by sorting signals, are packaged into COP II vesicles for transport to the Golgi. What is the role of retrieval sequences like KDEL in protein transport between the ER and Golgi?
Retrieval sequences such as KDEL act as tags on proteins that mistakenly leave the ER, directing them to be returned from the Golgi back to the ER via specific vesicles. Differentiate between anterograde and retrograde transport in the context of the Golgi apparatus.
Anterograde transport moves proteins from the ER through the Golgi to the plasma membrane, while retrograde transport moves proteins from the plasma membrane or Golgi back to the ER. The Golgi uses sorting signals and receptors to direct these pathways. What is the role of COP II vesicles in protein transport from the ER to the Golgi apparatus?
COP II vesicles transport properly folded proteins marked with sorting signals from the ER to the Golgi apparatus. Only proteins that are correctly folded and processed are packaged into these vesicles for export. How are the cis, medial, and trans regions of the Golgi apparatus organized, and what is their significance?
The Golgi apparatus is organized into cis (facing the ER), medial (middle), and trans (facing the plasma membrane) regions, each made up of flattened stacks called cisternae. Each region is responsible for specific protein modifications and sorting functions. What are the two main models explaining how proteins move through the Golgi apparatus?
The vesicular transport model suggests proteins move in vesicles between stationary cisternae, while the cisternae maturation model proposes that cisternae themselves move and mature from cis to trans. Current evidence indicates that both models operate together in protein transport through the Golgi.
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