Which of the following macromolecules are not made primarily of carbon, hydrogen, and oxygen?

Proteins are indeed the correct answer as they are distinct from carbohydrates and lipids in their composition. While proteins do contain carbon, hydrogen, and oxygen, they also incorporate nitrogen in their amino acid structure, which is essential for forming the peptide bonds that link amino acids together to create proteins. This nitrogen presence is what sets proteins apart from carbohydrates and lipids, which strictly consist of carbon, hydrogen, and oxygen.

Carbohydrates are formed from carbon, hydrogen, and oxygen, typically in a ratio that reflects the empirical formula (CH2O)n. Lipids also conform to this framework, although their structures can be more complex and often contain long hydrocarbon chains or ring structures. However, they do not include nitrogen in their basic structure, unlike proteins. Therefore, the unique inclusion of nitrogen in proteins underscores why they are the correct answer as the macromolecules that are not made primarily of just carbon, hydrogen, and oxygen.