Final answer:
Amino acids located in the ER lumen of a transmembrane protein after translation will subsequently be found in the Golgi apparatus, where they are further modified and sorted before reaching their final destination.
Step-by-step explanation:
As a newly translated transmembrane protein is processed through the cell, amino acids situated in the Endoplasmic Reticulum (ER) lumen, post-translation, end up in the lumen of the Golgi apparatus. After translation in the rough ER, proteins destined for the plasma membrane or for secretion are packaged into transport vesicles. These vesicles then move to the Golgi apparatus, where the proteins are further modified and sorted. The cis face of the Golgi apparatus receives these vesicles, and after processing, the proteins move towards the trans face, finally getting packaged into additional vesicles that either fuse with the plasma membrane or deliver the proteins to other organelles or be secreted outside the cell.
The correct answer to where the amino acids located in the ER lumen would be after the protein undergoes processing and leaves the ER is the Golgi apparatus. This organelle plays a central role in modifying, sorting, and packaging proteins to their final destinations, whether it's the cell membrane or various other organelles within the cell.