Review Question - QID 100074

In disrupting alpha helices, the compound affected hydrogen bonds. Alpha helices and beta pleated sheets are both examples of secondary structures assumed by a protein due to hydrogen bonds between amino acids.

Primary structure refers to the sequence of amino acids, held together by covalent peptide bonds. Tertiary structure is the shape assumed by the protein after folding that is held tightly together by ionic bonds, hydrophobic interactions, disulfide bonds (between two cysteine residues which also provide the protein its ability to resist denaturation), and further hydrogen bonding. Quaternary structure is the shape assumed if multiple polypeptide chains form the protein.

Dobson reviews the mechanisms of protein folding. He notes that protein folding is not due to a series of defined steps but rather to a probabilistic, trial-and-error process in which the lowest-energy conformations are favored. Additionally, protein misfolding is implicated in many neurodegenerative diseases, including Alzheimer disease.

Rossman and Argos discuss the levels of protein structure. They describe how nitrogen and oxygen atoms bond with hydrogen atoms on neighboring amino acids to produce secondary structures. They also note that tertiary structure contributes to formation of active "domains" which are conserved across enzymes in different species.

Illustration A shows the structure of a-helices and b-pleated sheets.
Illustration B shows the 4 levels of protein folding.

Incorrect Answers:
Answer 1: The primary structure of the protein refers to the sequence of amino acids.
Answer 3: Covalent peptide bonds between carboxyl and amino groups of amino acids lead to formation of an amino acid chain, or primary structure of a protein.
Answer 4: Ionic bonds between amino acids are part of a protein's tertiary structure.
Answer 5: Disulfide bonds are part of a protein's tertiary structure.