The next two amino acids that we're going to focus on will be the aromatic amino acids phenolalamine and tyrosine. And we're going to look at how our liver cells can metabolize these two amino acids, ultimately forming acetylacetate and fumarate. Now, acetoacitate can be used by hepatocytes to form ketone bodies, while fumerate can be be used to form glucose. And that's exactly why these two amino acids, phenylalanine and tyrosine, are known as glucogenic and ketonic amino acids, because we can use them to ultimately form both glucose and ketone bodies. So let's begin by examining step one. And actually what step one shows us is we can transform phenylalanine directly into tyrosine.