Well, for the most part, the amino acid can be used in biosynthetic processes to form new molecules. For example, we can use amino acids to build proteins. We can use amino acids to build nucleotide bases. But let's suppose we have all the proteins that we want, and we have all the nucleotide bases that our cells can actually use. What happens to any extra leftover amino acids? Well, you might be thinking we can store those amino acids for later use.