Which of the following functional groups contains a carbon atom double-bonded to an oxygen atom ($C=O$)?

Which of the following functional groups contains a nitrogen atom ($N$)?

Which of the following functional groups is essential in the structure of amino acids, which are vital to living organisms?

Which functional group typically has a negative charge at the $\mathrm{pH}$ of the cell?

Which of the following functional groups is characterized by a carbon-oxygen double bond ($C=O$)?

Which of the following is a functional group commonly found in organic molecules?

Which of the following is a characteristic feature of an aldehyde functional group?

Which of the following functional groups is present in all amino acids?

Which statement about a methyl functional group is correct?