Question

the endoplasmic reticulum (er) is a network of membranes involved in various cellular processes. how does the rough er directly contribute to protein synthesis? it modifies and packages proteins for transport. it contains ribosomes that synthesize proteins destined for secretion or insertion into membranes. it detoxifies harmful substances within the cell. it synthesizes lipids and steroids. the golgi apparatus is often compared to a \post office\ of the cell. what is its main role in relation to proteins synthesized in the er? to transcribe the genetic code into messenger rna for protein synthesis. to break down and recycle faulty proteins. to fold the proteins into their correct three - dimensional structures. to further modify, sort, and package proteins for delivery to other organelles or secretion out of the cell.

Explanation:

The rough endoplasmic reticulum (ER) has ribosomes attached to its surface. These ribosomes synthesize proteins that are either secreted out of the cell or inserted into membranes. The Golgi apparatus modifies, sorts, and packages proteins received from the ER for delivery to other organelles or for secretion out of the cell.
For the first question, the other options are functions of other cellular components or of the smooth ER. Modifying and packaging for transport is more of a Golgi - related function, detoxification is a smooth ER function, and lipid/steroid synthesis is also a smooth ER function.
For the second question, transcription occurs in the nucleus, breaking down and recycling faulty proteins is a function of lysosomes, and protein folding mainly occurs in the ER itself with some assistance in the Golgi but its main role is modification, sorting and packaging.

Answer:

1. It contains ribosomes that synthesize proteins destined for secretion or insertion into membranes.
2. To further modify, sort, and package proteins for delivery to other organelles or secretion out of the cell.