Jackson performed an experiment in which he analyzed the elemental components of several unknown compounds. His results are shown in the table below. Elemental Components of Unknown Compounds Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur

Given this data, Jackson concludes that only Unknown 2 could be a protein. Which of the following explanations supports Jackson's conclusion?

A. Proteins have some amino acids that contain nitrogen, whereas most lipids, nucleic acids, and carbohydrates do not contain nitrogen.

B. Proteins are the only macromolecules that contain carbon, hydrogen, and oxygen.

C. Proteins have some amino acids that contain sulfur, whereas most lipids, nucleic acids, and carbohydrates do not contain sulfur.

D. Proteins are the only macromolecules that contain carbon, hydrogen, oxygen, and phosphorus.

The correct answer is option (C) Proteins have some amino acids that contain sulfur, whereas most lipids, nucleic acids, and carbohydrates do not contain sulfur.

Carbohydrates are biomolecules made up of carbon (C), hydrogen (H) and oxygen (O) only. Lipids are organic molecules made up of carbon (C) as their backbone along with hydrogen (H) and oxygen (O). In addition they can contain nitrogen (N) and phosphorus (P). Nucleic acids are the biological molecules made up of carbon (C), hydrogen (H), oxygen (O), nitrogen (N) and phosphorus (P).

Proteins are the only group of organic compounds made up of sulfur (S) in addition to the carbon (C), hydrogen (H), oxygen (O) and nitrogen (N) of the aminoacids which form the monomers of the proteins. Thus, the other biomolecules like carbohydrates, lipids and nucleic acids lack sulfur and compound unknown 2 being analysed by Jackson can only be a protein because of the presence of sulfur.