Final answer:
The position of an amino acid in a protein affects its structure and function. R groups contribute to properties like shape and solubility, and mutations causing substitutions can lead to conditions like sickle-cell disease by altering protein configuration.
Step-by-step explanation:
The Effect of Amino Acid Position in Proteins
The position of an amino acid residue relative to its neighbors can result in significant effects on the protein's structure and function. The amino acid side chains, also known as R groups, come with various properties such as size, shape, solubility, and ionization potential, which influence the protein's behavior. The primary structure of proteins, which is the unique sequence of amino acids, determines the higher levels of protein structures such as the secondary, tertiary, and quaternary configurations. Mutation or substitution mutations that alter the position of an amino acid can drastically change the protein's properties, sometimes resulting in diseases like sickle-cell anemia due to the replacement of one amino acid by another, changing the protein's shape and function.
For example, a change in a single nucleotide in the hemoglobin gene can cause sickle-cell disease by substituting valine for glutamic acid, dramatically altering the hemoglobin molecule's structure and function. Hence, any mutation or alteration that changes the sequence of amino acids can have profound biological implications due to the sequence's direct impact on protein folding and stability, indicated by concepts such as the N-end rule.