What is true about the nature of peptide bonds?

The assertion regarding peptide bonds being polar but uncharged is accurate and reflects essential characteristics of peptide bonds in proteins. Peptide bonds form through a condensation reaction between the amino group of one amino acid and the carboxyl group of another, resulting in the release of water. This bond has a significant dipole moment, indicating that it exhibits polarity due to the difference in electronegativity between the carbon (of the carbonyl) and nitrogen atoms.

Despite being polar, peptide bonds do not have a formal charge, as they involve the sharing of electrons between the atoms. This property is crucial because it influences how proteins interact with their environment and other molecules, affecting their overall structure and function.

The other options describe characteristics that do not accurately reflect the nature of peptide bonds. For instance, peptide bonds do have a partial double-bond character due to resonance, restricting rotation around the bond itself and thus contributing to the planarity of the bond. This planarity is crucial for the formation of secondary structures such as alpha-helices and beta-sheets in proteins. Understanding these properties is fundamental when studying protein structure and function.