This is a great subject to discuss because multiple MCAT-2015 resources out there are giving specific advice to "not memorize" amino acid names and abbreviations. I'd say that if the AAMC has shown one trend for biochem in the pre-released MCAT-2015 materials it is that amino acids are going to be heavily tested. The abbreviations won't likely be tested themselves. MCAT authors rarely ask question like "Which is the 1-letter abbreviation for arginine." But they will ask you to understand the chemistry of each of the amino acids in such a way that you can predict that tyrosine will be likely to be in the active site of enzyme x because it binds a hydrophobic substrate, while lysine (+ charged) would be less likely--and the answers options to those questions could be presented as either 1- or 3-letter abbreviations so if you don't know them you'll be left guessing.
