MICROANATOMY

Detailed explanation-1: -The RER is associated with many roles in protein synthesis, which also include post-translational modifications, folding, and sorting. Membrane-bound ribosomes in the RER translate the mature mRNA transcript into amino acids that are attached to become polypeptides.

Detailed explanation-2: -From the RER, proteins move into a transitional region of the ER lumen, which is largely lacking in ribosomes. Some proteins, such as secretory proteins, which are released by cells, are packaged in vesicles and move to the Golgi apparatus.

Detailed explanation-3: -The correct answer is option 2, i.e. 70S. Ribosomes are the protein factory in a cell. They are found in the Rough Endoplasmic Reticulum(RER) and cytoplasm. 80S type of ribosomes is found in the eukaryotic cell whereas 70S types of ribosomes are found in the prokaryotic cells.

Detailed explanation-4: -The ribosome that is synthesizing the protein is directly attached to the ER membrane. These membrane-bound ribosomes coat the surface of the ER, creating regions termed rough endoplasmic reticulum, or rough ER (Figure 12-36A).