Final answer:
Phenylalanine is an essential amino acid denoted by the three-letter code 'Phe' and the one-letter code 'F'. It has a nonpolar side chain and is critical for protein synthesis and neurotransmitter production, with its metabolism being crucial for health.
Step-by-step explanation:
Phenylalanine, represented by the three-letter code 'Phe' and the one-letter code 'F', is one of the 20 common amino acids found in proteins. Its distinctive feature is a nonpolar side chain, which makes it hydrophobic. Amino acids are the building blocks of proteins, with each having a unique side chain that imparts different chemical properties to the protein. Phenylalanine is an essential amino acid, meaning our bodies cannot synthesize it and therefore, it must be obtained through our diet. It can be converted into another amino acid, tyrosine, which is crucial for protein synthesis and the production of neurotransmitters. A defect in the metabolism of phenylalanine, such as seen in the genetic disorder phenylketonuria, can cause serious health problems.