Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

What essential organic molecules is phosphorus a critical component of?

1. Proteins

2. Carbohydrates

3. Fats

4. Nucleic acids

The correct answer is: Nucleic acids

Phosphorus is a critical component of nucleic acids, which include DNA and RNA. These molecules are essential for storing and transmitting genetic information within living organisms. The structure of nucleotides, the building blocks of nucleic acids, contains a phosphate group that includes phosphorus. This phosphate group is fundamental for the formation of the backbone of the DNA and RNA strands, linking the sugar molecules and providing structural stability to these molecules. In contrast, while proteins, carbohydrates, and fats are vital organic molecules that play key roles in biological systems, they do not contain phosphorus as a structural component in the same fundamental way that nucleic acids do. Proteins are composed of amino acids, carbohydrates are made up of sugar units, and fats consist of fatty acids and glycerol, none of which typically involve phosphorus in their basic structures. Therefore, the association of phosphorus with nucleic acids underscores its essential role in genetic processes and cell function.