Algonquin College Health Program Assessment (AC-HPAT) Practice Exam

Carbohydrates are primarily composed of which three elements?

1. Carbon, hydrogen, and nitrogen

2. Hydrogen, oxygen, and sulfur

3. Carbon, hydrogen, and oxygen

4. Nitrogen, phosphorus, and carbon

The correct answer is: Carbon, hydrogen, and oxygen

Carbohydrates are predominantly made up of carbon, hydrogen, and oxygen. This composition is fundamental to their structure and function. Specifically, carbohydrates can be represented by the general formula Cn(H2O)n, which highlights the ratio of hydrogen and oxygen atoms to carbon atoms. This molecular structure is crucial as it allows carbohydrates to serve as a major energy source for living organisms, as well as playing structural roles in plants (e.g., cellulose) and other biological functions. The other combinations of elements mentioned are not characteristic of carbohydrates. For example, nitrogen is not a primary component of carbohydrates; its presence is more associated with proteins and nucleic acids. Similarly, sulfur and phosphorus are elements found in proteins and certain other biomolecules but do not pertain to the carbohydrate structure. Understanding the basic composition of carbohydrates helps in distinguishing them from other macromolecules in biochemistry.