What type of bonds hold polypeptide chains together to form complex proteins?

• A. Covalent bonds
• B. Phosphodiester bonds
• C. Ester bonds
• D. Noncovalent bonds

Answer: (D)

Verified step by step guidance

1. Understand that polypeptide chains are sequences of amino acids linked by peptide bonds, which are covalent bonds.
2. Recognize that the question is asking about the interactions that stabilize the three-dimensional structure of proteins, not the bonds that link amino acids in a chain.
3. Identify that noncovalent interactions, such as hydrogen bonds, ionic bonds, van der Waals forces, and hydrophobic interactions, play a crucial role in maintaining the protein's structure.
4. Differentiate between the types of bonds: covalent bonds are strong and involve sharing electrons, while noncovalent bonds are weaker and involve various types of attractions.
5. Conclude that while covalent bonds form the primary structure of proteins, noncovalent bonds are essential for the secondary, tertiary, and quaternary structures, which give proteins their functional shapes.