Which of the following is NOT attached to the central (alpha) carbon atom in a standard amino acid?

• A. A carboxyl group (\(-COOH\))
• B. A phosphate group (\(-PO_4^{3-}\))
• C. A hydrogen atom (\(-H\))
• D. An amino group (\(-NH_2\))

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by recalling the general structure of a standard amino acid. Amino acids are the building blocks of proteins and share a common structure consisting of a central (alpha) carbon atom.
2. Step 2: Identify the four groups typically attached to the alpha carbon in a standard amino acid. These include: (1) a carboxyl group (\(-COOH\)), (2) an amino group (\(-NH_2\)), (3) a hydrogen atom (\(-H\)), and (4) a variable side chain (R group).
3. Step 3: Examine the options provided in the question. Compare each group listed to the standard structure of an amino acid to determine which one is not typically attached to the alpha carbon.
4. Step 4: Note that a phosphate group (\(-PO_4^{3-}\)) is not part of the standard structure of an amino acid. Phosphate groups are commonly found in nucleotides and other biomolecules, but they are not attached to the alpha carbon in amino acids.
5. Step 5: Conclude that the correct answer is the phosphate group (\(-PO_4^{3-}\)), as it is not one of the four groups attached to the alpha carbon in a standard amino acid.