Final answer:
Amino acid substitutions can alter the secondary and tertiary structures of proteins, like in sickle cell anemia where a single substitution changes hemoglobin's structure and function.
Step-by-step explanation:
Impact of Amino Acid Substitution on Protein Structure
A change in the primary structure of a protein, which is its unique amino acid sequence, can significantly affect its secondary and tertiary structures. The secondary structure refers to local folds such as alpha helices and beta sheets, which are influenced by hydrogen bonds between amino acid side chains. A substitution in the amino acid sequence may alter these local structures, potentially leading to a dramatic change in the tertiary structure, or the protein's three-dimensional shape due to side chain interactions. Such a change is exemplified by the alteration seen in hemoglobin causing sickle cell anemia, where the substitution of glutamic acid by valine leads to a malformed protein that affects red blood cell shape and function.