And alpha simply means that the residue is attached to our alpha carbon, that our group is attached to our alpha carbon with respect to our carbonyl group. Now, ten of these amino acids can actually be synthesized by our body without any problem, without actually having to ingest any type of food. But the other ten, which are known as essential amino acids, we cannot actually synthesize. We must actually ingest them from food products. And we need all 20 amino acids to basically survive, even if we are missing a single amino acid. That means we do not have the proper amount of amino acids in our body to synthesize all the proteins that are needed by the body to survive.