AP BIOLOGY

Detailed explanation-1: -Organic bases are usually, but not always, proton acceptors. They usually contain nitrogen atoms, which can easily be protonated. For example, amines or nitrogen-containing heterocyclic compounds have a lone pair of electrons on the nitrogen atom and can thus act as proton acceptors.

Detailed explanation-2: -This means that all organic compounds have in common the presence of carbon atoms and hydrogen atoms. In addition, different organic compounds may contain oxygen, nitrogen, phosphorous, and other elements. Carbon dioxide (CO2) does not have hydrogen; then, it is not an organic compound.

Detailed explanation-3: -Nitrogen forms many organic compounds including amines, amino acids, amino alcohols, amides and lactams, nitro compounds, imines, nitriles, diazonium salts, hydrazides, carbazides, oximes, and heterocyclic compounds such as imidazole, triazole, and tetrazole.

Detailed explanation-4: -Functional groups containing oxygen atoms: carbonyl group C=O, alcohol R-OH, and ether R-O-R. The lone pair electrons on O in these groups are able to accept the protons, so functional groups like aldehyde, ketone, alcohol and ether are all organic bases.

Detailed explanation-5: -So the correct option is ‘carbon’.