From the rough endoplasmic reticulum, proteins are often sent to the for further posttranslational modification:

The proteins are sent to Golgi apparatus from the rough endoplasmic reticulum for the purpose of the post-translational modification.

The Golgi apparatus or the Golgi complex packages these delivered proteins into new vesicles. This process is carried by the various enzymes which are present in the Golgi complex. When done, these proteins bud from the surface of the complex in the new vesicles which migrate to the cell membrane.

Hence, the blank can be filled with 'Golgi apparatus'.

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.

allowed for the prediction of the properties of missing elements.