Sequences of amino acids come into the picture, when you study the structure of peptide chains and proteins.
About Amino Acids
They are carbon compounds, made from an amine group (-NH2), carboxylic acid group (-COOH), and a chain of carbon molecules of varying types. The extra chain of carbon atoms, that connect the carboxylic acid and amino group ends, often dubbed as the 'R-group', determine their nature and type.
They are important molecules in the chemistry of life and form the building blocks of proteins. Just as 26 letters of the alphabet combine together to form various words, the more than hundred known amino acids combine to form proteins. Among them, there are 20 essential amino acids that form all the proteins in the human body. They make up most of the enzymes and proteins that drive the body functions. Their supplements are used in the cure of many diseases.
Sequences in Proteins
An amino acid sequence is the order in which various acids get linked to form a protein or a peptide chain. A peptide chain is a long covalently-bonded chain of acids. If a peptide chain, happens to be a protein, its alignment sequence is called its 'Primary Structure'. Branched chain amino acids form all the proteins of the human body.
Proteins and peptide chains are created through the formation of peptide bonds between different amino acids. Their sequence is created through the bonding of the carboxyl group of one amino acid, with the amino group of another. This kind of linking goes on until polypeptides are created. To study any protein or for that matter, any molecule in chemistry, one needs to understand its structure first. That's why, to study a protein, a biochemist must first find out its amino acid structure. A protein is much more complex than a peptide chain, with hundreds or thousands of these acids bonding together.
The formation of proteins happens at the cellular level. The recipe or the code for creation of any protein is encoded in the DNA (Deoxyribonucleic Acid) molecule. To create every protein, the recipe for creation, must first be deciphered from the DNA molecule and then relayed to the site of protein synthesis. The deciphering part is done by the mRNA (messenger RNA) strand that holds information about creating a protein from a gene. Every amino acid has a specific three letter corresponding code (called a codon), in the DNA sequence.
This mRNA code has a sequence of codons, which provides the order of assembling various amino acids together. From the strand of mRNA, that is transported in the cytoplasm, tRNA (transfer RNA) carry the information about the sequence, to a ribosome site for protein assembly. So, the order of a sequence, if known, can be used to decipher the corresponding DNA code segment or gene that created it, through reverse engineering.
The sequence of amino acid arrangement in a protein, is itself created according to the translation of the genetic code of a gene. Biochemistry is a truly amazing field of study and the deeper you delve into it, the more will you know about the mystery of life.