USA Biology Olympiad (USABO) Practice Exam

Which molecule is primarily responsible for providing energy to cellular processes?

1. DNA

2. ATP

3. RNA

4. Glucose

The correct answer is: ATP

ATP, or adenosine triphosphate, is the primary energy carrier in all living cells. It serves as a crucial molecule that stores and transfers energy within cells, facilitating various biochemical processes. When ATP is hydrolyzed, it releases energy that can be utilized for activities such as muscle contraction, active transport across membranes, and biosynthesis of macromolecules, among other cellular functions. While glucose is a significant energy source and is metabolized to produce ATP, it is not the molecule that directly fuels cellular processes. Instead, glucose undergoes metabolic pathways (like glycolysis and the Krebs cycle) to generate ATP. DNA and RNA have roles in genetic information storage and protein synthesis, respectively, but they do not serve as direct energy carriers within the cell. Thus, ATP stands out as the molecule specifically designed for the efficient transfer and storage of energy, making it central to the myriad energy-dependent reactions occurring in cells.