Chapter 4, Problem 4.7PS

Protein Synthesis and Secretion. Although we will not encounter protein synthesis and secretion in detail until later chapters, you already have enough information about these processes to order the seven events that are now listed randomly. Order events 1–7 so that they represent the correct sequence corresponding to steps a–g, tracing a typical secretory protein from the initial transcription (readout) of the relevant genetic information in the nucleus to the eventual secretion of the protein from the cell by exocytosis.

Transcription → (a) → (b) → (c) → (d) → (e) → (f) → (g) → Secretion

1. The protein is partially glycosylated within the lumen of the rough ER.

2. The secretory vesicle arrives at and fuses with the plasma membrane.

3. The RNA transcript is transported from the nucleus to the cytoplasm.

4. Final sugar groups are added to the protein in the Golgi apparatus.

5. As the protein is synthesized, it passes across the ER membrane into the lumen of the rough ER, and from there via a vesicle to the Golgi apparatus.

6. The protein is packaged into a secretory vesicle and released from the Golgi apparatus.

7. The RNA message associates with a ribosome and begins synthesis of the desired protein on the surface of the rough ER.