[Campbell Biology P.126] Which statement accurately describes the general representation of ... | Practice Question

Which statement accurately describes the general representation of amino acids based on Figure 5.14?

  • A: Amino acids are typically shown in their non-ionized form at physiological pH.
  • B: The ionized form, prevalent at cellular pH (7.2), features a positively charged amino group and a negatively charged carboxyl group.
  • C: All amino acids used in proteins are D enantiomers.
  • D: The side chain (R group) is always a simple hydrogen atom.

Explanation

The introductory text and the top right diagram in Figure 5.14 clearly show that amino acids are depicted in their ionized form, which is prevalent at cellular pH 7.2 . In this form, the amino group is positively charged H3N+ and the carboxyl group is negatively charged COO- . The figure also states that all amino acids in proteins are L enantiomers, and their R groups vary in complexity, not just a simple hydrogen.