Final answer:
The primary structure of a protein, which is determined by its amino acid sequence, affects how the protein folds and its final 3D structure, leading to specific functions.
Step-by-step explanation:
The differences in amino acid sequences lead to different protein functions by altering the protein's primary structure. Each amino acid has unique chemical properties, so the sequence of amino acids determines how the protein folds and its eventual 3D structure. This structure dictates the protein’s abilities and functions because different shapes and chemical properties allow the protein to interact with other molecules in specific ways. When a mutation causes a change in the amino acid sequence, it can result in a modified protein with a new role, or it might not function at all. As such, the primary structure is crucial since it directly influences higher structures (secondary, tertiary, quaternary) and ultimately determines the protein's function.