Final answer:
The three-letter abbreviation 'Leu' represents the amino acid leucine, which is one of the essential amino acids that humans must obtain through their diet. Amino acids are also represented by a single letter, such as 'V' for valine, and are crucial for protein synthesis, a process dictated by the genetic code.
Step-by-step explanation:
A three-letter abbreviation such as 'Leu' stands for a specific amino acid, in this case, leucine. Amino acids are the building blocks of proteins and are represented either by a three-letter abbreviation or by a single upper case letter. For instance, valine can be represented by 'Val' or 'V'. In the human diet, certain amino acids are considered essential amino acids, meaning the body cannot synthesize them on its own and must obtain them from the diet. These include isoleucine, leucine, and cysteine, among others.
The genetic code dictates how sequences of three nucleotide bases - known as codons - in RNA are translated into amino acids during protein synthesis. Each codon corresponds to one amino acid or a stop signal during the translation process. The unified language of the genetic code means that virtually all organisms use the same code to produce proteins from RNA sequences, though what counts as an essential amino acid can vary amongst different organisms.
The primary structure of a protein is defined by its sequence of amino acids, which can be represented in shorthand using the three-letter abbreviations for each amino acid. For example, a peptide sequence might be written as 'Gly-His-Lys' to represent glycine-histidine-lysine. This format aids in understanding the structure and function of proteins.