Initiation of protein synthesis begins on which of the following sites?
- Free-standing ribosomes
- Rough endoplasmic reticulum
- Golgi apparatus
- I only
- II only
- I and II
- I, II, and III
- True. Translation is always initiated on free-free standing ribosomes in the cytosol.
- False. Proteins that are destined for secretion are initially translated on ribosomes in the cytoplasm. A signal sequence is first translated at the N-terminus of the peptide, which becomes the site of attachment for signal-recognition particles (SRP). The nascent protein is then directed to the rough endoplasmic reticulum by the SRP for further translation at the ER and packaging in the Golgi.
- False. The Golgi apparatus is responsible for packaging proteins that are to be secreted by the cell.
Answer: A. See explanations above.
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