Which functional groups are present in the general structure of an amino acid?

• A. An amino group (\(-NH_2\)) and a carboxyl group (\(-COOH\))
• B. A hydroxyl group (\(-OH\)) and a methyl group (\(-CH_3\))
• C. A phosphate group (\(-PO_4^{3-}\)) and a sulfhydryl group (\(-SH\))
• D. A carbonyl group (\(>C=O\)) and an aldehyde group (\(-CHO\))

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the general structure of an amino acid. Amino acids are the building blocks of proteins and have a central carbon atom (called the alpha carbon) bonded to four different groups: an amino group ( $-N_{\mathrm{H}}2$), a carboxyl group ( $-{\mathrm{COOH}}_{}$), a hydrogen atom, and a variable side chain (R group).
2. Step 2: Analyze the functional groups listed in the options. Identify which of these groups are part of the general structure of an amino acid. For example, the amino group ( $-N_{\mathrm{H}}2$) and the carboxyl group ( $-{\mathrm{COOH}}_{}$) are always present in amino acids.
3. Step 3: Eliminate options that include functional groups not found in the general structure of amino acids. For example, a hydroxyl group ( $-{\mathrm{OH}}_{}$) or a methyl group ( $-{\mathrm{CH}}_3$) are not part of the general structure but may appear in specific side chains.
4. Step 4: Confirm that the amino group ( $-N_{\mathrm{H}}2$) and carboxyl group ( $-{\mathrm{COOH}}_{}$) are the correct functional groups present in all amino acids, as these are essential for their structure and function.
5. Step 5: Conclude that the correct answer is the option containing the amino group ( $-N_{\mathrm{H}}2$) and the carboxyl group ( $-{\mathrm{COOH}}_{}$), as these are universally present in the general structure of amino acids.