A Level Biology Practice Exam

Which element is NOT typically found in nucleic acids?

1. Carbon

2. Oxygen

3. Helium

4. Nitrogen

The correct answer is: Helium

Nucleic acids, which include DNA and RNA, are fundamental biomolecules that carry genetic information. They are composed of nucleotides, which are made up of a sugar, a phosphate group, and a nitrogenous base. The elements commonly found in these components include carbon, oxygen, nitrogen, and phosphorus. Carbon is a key building block in the sugar and base structures, oxygen is present in the sugar and phosphate groups, and nitrogen is a key component of the nitrogenous bases. Helium, on the other hand, is an inert noble gas and does not play any role in the structure or function of nucleic acids. Its non-participation in chemical bonding at the molecular level makes it absent from nucleic acids, supporting the selection of this answer.