Final answer:
When one amino acid is changed in a polypeptide, it alters the primary structure of the protein, which can affect its secondary, tertiary, and quaternary structures.
Step-by-step explanation:
In a polypeptide, when one amino acid is changed, it will alter the primary structure of the protein. The primary structure refers to the unique sequence of amino acids in the polypeptide chain. Altering a single amino acid can change the genetic code and lead to a different protein being produced.
The change in the primary structure can also affect the secondary, tertiary, and quaternary structures of the protein. The secondary structure, such as alpha-helix or beta-pleated sheet, is maintained by hydrogen bonds between amino acids in different regions of the polypeptide. The tertiary structure is the overall folded 3D structure of the entire polypeptide chain, and it is held by various interactions like disulfide linkages and hydrogen bonding. The quaternary structure involves interactions between two or more tertiary subunits.
Therefore, when a single amino acid is changed in a polypeptide, it can have a significant impact on the structure and function of the protein.