Question

once insulin is inside the er, proteins there do two key things: they remove the signal sequence and assist the process of folding the primary sequence into the proteins correct secondary and tertiary structure. although this doesnt happen for insulin, in many cases other proteins inside the er add short carbohydrates to newly folded proteins. suppose that you could synthesize an mrna with a random sequence of nucleotides but attach the information for a normal signal sequence to one end, and that you could mark the molecule so you can observe what happens to it after you introduce it to the interior of a cell. choose the most logical prediction. it would not enter the er, because the mrna sequence is random and not meaningful in terms of the cells fitness. it would not enter the er, because the signal sequence only works for the insulin protein. the signal sequence would bind to the rna - protein particle and the protein would enter the er. in this cartoon version of the \enter er\ model (on the left here), which of the 3 stages would correspond to the way
ough er\ looks in many microscope images? select all that apply.

Explanation:

1. For the mRNA - related question: Signal sequences are recognized by the cell's machinery for protein targeting to the ER. Even with a random mRNA sequence, if it has a normal signal sequence, the signal sequence would bind to the RNA - protein particle (such as the signal - recognition particle) and facilitate the entry of the associated protein into the ER.
2. For the rough ER question, the rough ER appears rough under a microscope because of the presence of ribosomes attached to its surface. Without the stages shown, we can't answer that part fully, but for the mRNA question, the reasoning is based on the general principle of signal - sequence - mediated protein targeting.

Answer:

The signal sequence would bind to the RNA - protein particle and the protein would enter the ER.