If you think of a protein as analogous to a word in the English language, then the amino acids are like letters. The comparison is not altogether fanciful, as there are about as many amino acids in proteins as letters in the alphabet, and the order of both amino acids and letters is important. For example, the word PROTEIN has the same letters as POINTER, but the two words have completely different meanings. Similarly, the exact order of amino acids in a protein determines the protein’s shape and function.