Amino Acid Synthesis

Amino acids are created in an astounding number of ways within our bodies. Creating them artificially in a lab proved a bit harder but ultimately two tried and true methods were discovered and are now widely used.

We could go down the rabbit hole with both and spend way too much time learning the mechanism and exact steps needed to create them but honestly, that is probably a waste of your time. Instead let’s look at the general features, similarities, and differences between the two methods and move on to the far more important material on peptides and proteins.

Strecker Synthesis

The Strecker synthesis begins with an aldehyde, ammonium chloride (NH4Cl), and potassium cyanide (KCN) and ends up with an amino acid as its end product. The starting aldehyde contains the desired side chain and will result in a racemic mixture of both L and D amino acids.

This occurs because we started with a planar molecule and without a stereospecific enzyme, as we would have in vivo, the molecule can be attacked from both the top and the bottom. Ultimately, this results in a racemic mixture of amino acids only half of which are actually biologically useful.

Gabriel Synthesis

The Gabriel synthesis on the other hand starts with a drastically different set of reactants specifically, potassium phthalimide and diethyl bromomalonate. Despite the drastically different reagents involved the Gabriel synthesis also yields are a racemic mixture of L and D amino acids since once again the starting materials are both planar.

While there is a lot more to these reactions than just the few tidbits mentioned above this is plenty for the MCAT. Just make sure you know the starting materials of each reaction and that both result in a racemic mixture of amino acids rather than just the biologically useful L-amino acids that we make in our bodies.

In vivo translates to in life and represents what would be found in a fully functional cell. Since our cells possess stereoselective enzymes we only make L-amino acids. In vitro, on the other hand, translates to in a test tube and represents isolated processes that are carried out in test tubes rather than cells. This is why in addition to starting with a planar molecule both the Strecker and Gabriel synthesis result in racemic mixtures of the amino acids.