The question is, how exactly does a cell actually know which one of these amino acids must be glycosylated? Well, the way that it knows is it looks at the sequence next to that particular amino acid. So the size at which glycosylation takes place depends on the sequence of amino acids adjacent to that particular amino acid. So in the case of a sparrogene, the cell will only modify the spare gene and attach that particular sugar molecule if the sequence around is a specific sequence. And these are the two sequences that the cell uses. So right next to the spargian, ASM asparagine, we have to have an arbitrary x, so an arbitrary amino acid where x cannot be proline.