Ecco perché:

* Primary structure is the linear sequence of amino acids in a protein chain. It's like the alphabet of a protein, determining the order of its building blocks.

* Secondary structure refers to local folding patterns within the protein chain, such as alpha-helices and beta-sheets.

* Struttura terziaria describes the overall three-dimensional shape of a single protein molecule.

* Quaternary structure is the arrangement of multiple protein subunits (polypeptide chains) in a complex.

So, the amino acid sequence directly defines the primary structure of a protein.