Which of the following enables a cell to pick up and concentrate a specific kind of molecule?
1) passive transport
2) facilitated diffusion
3) osmosis
4) receptor-mediated endocytosis
5) channel proteins

The correct answer is option 4

Receptor mediated endocytosis is an endocytotic mechanism which involves ingestion of foreign molecules into the cell. It forms a receptor-ligand interaction. The receptors bind to the targetted  ligands on the outside of the cell

Receptors on the plasma membrane of the target tissue will specifically bind to ligands on the outside of the

answer; a muscle cell, another neuron and a of the above

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.