Question

living systems are made of complex molecules including carbohydrates, fats, proteins, and nucleic acids. even though there are more than 100 elements known to exist, these molecules are comprised of only a few elements. what are these elements?
a. carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur
b. sodium, potassium, calcium, nitrogen, phosphorus, sulfur
c. carbon, hydrogen, oxygen, fluorine, chlorine, iodine
d. fluorine, chlorine, iodine, nitrogen, phosphorus, sulfur

Explanation:

To determine the elements that make up complex molecules in living systems (carbohydrates, fats, proteins, nucleic acids), we analyze each option:

• Carbohydrates and fats (lipids) are mainly composed of carbon, hydrogen, and oxygen. Proteins contain carbon, hydrogen, oxygen, nitrogen, and often sulfur. Nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.
• Option A includes carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur, which matches the key elements of these biomolecules.
• Option B includes sodium, potassium, calcium (more related to electrolytes/ions in cells, not main components of these molecules).
• Option C includes fluorine, chlorine, iodine (halogens, not main components of these biomolecules).
• Option D includes fluorine, chlorine, iodine (halogens, not main components of these biomolecules).

Answer:

A. carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur