Certified Transport Registered Nurse Certification Practice Exam

Which type of molecules primarily compose the human body?

1. Oxygen

2. Hydrogen

3. Nitrogen

4. Carbon

The correct answer is: Nitrogen

The primary molecular composition of the human body consists significantly of carbon-based molecules, making carbon the most suitable answer in this context. Carbon is a fundamental building block of life, as it forms the backbone of biological macromolecules such as carbohydrates, lipids, proteins, and nucleic acids. These molecules are essential for various life processes, including energy storage, cellular structure, and genetic information encoding. While oxygen, hydrogen, and nitrogen are also critical components of the human body—contributing to the formation of water and various organic compounds—it is carbon that is uniquely capable of forming stable bonds with many elements, allowing for the vast complexity of organic chemistry necessary for life. Carbon's versatility is a key reason it is considered the primary element in biological molecules. Therefore, when evaluating the primary composition of the human body in terms of the types of molecules, carbon emerges as the most fundamental element.