The linear sequence of amino acids of a protein that is determined by genes.
The linear sequence is called a polypeptide chain and the amino acids are held together by covalent bonds
There are many different combinations of proteins as signified by the 20 amino acids. The possible combinations of a protein is represented by 20^n with n being the number of amino acids in the protein.
Peptide bonds stabilize the primary structure of proteins.
Changing the amino acids sequence can change the function of a protein and overall has a large effect on the higher level structure of the protein.