Macromolecules of Life – Zeringue Practice Test

The correct choice identifies the phosphate group as not being a primary component attached to the central carbon of amino acids. Amino acids are fundamentally characterized by having a central carbon atom bonded to four distinct groups: an amino group, a carboxyl group, a hydrogen atom, and a variable side chain or R group. The amino group (-NH2) serves as the basic part, allowing amino acids to function as the building blocks for proteins. In contrast, the carboxyl group (-COOH) provides the acidic property to the amino acid and is essential for peptide bond formation. The hydrogen atom is simply there to complete the tetravalent nature of the carbon atom.

The phosphate group, while important in biochemical processes, particularly in nucleotides and energy transfer (such as ATP), is not one of the standard components of amino acids. Therefore, it does not attach to the central carbon in this context. This highlights the unique structure and functional role of amino acids in protein synthesis, separate from the roles played by other macromolecules involved in cellular processes.