Advanced Placement (AP) Biology Practice Exam

What is an essential function of ATP in cells?

1. Store genetic information

2. Transfer oxygen molecules

3. Provide energy for cellular processes

4. Act as a substrate in photosynthesis

The correct answer is: Provide energy for cellular processes

ATP, or adenosine triphosphate, serves as the primary energy currency of the cell. Its essential function lies in providing energy for various cellular processes, including muscle contraction, active transport across membranes, and synthesis of macromolecules. When ATP is hydrolyzed, it releases energy that can be harnessed by enzymes and other proteins to drive biochemical reactions necessary for maintaining cellular functions. Although other options mention important biological processes, they do not pertain directly to the core function of ATP. For example, while genetic information storage is crucial, it is managed by nucleic acids such as DNA and RNA. The transfer of oxygen molecules is primarily the role of hemoglobin in red blood cells, not ATP. Moreover, while ATP is involved in the energy transformations during photosynthesis, it does not act as a substrate; rather, it is generated as a product of the light-dependent reactions to fuel the Calvin cycle. Thus, regarding energy provision, ATP is uniquely positioned as the key molecule that facilitates a multitude of cellular activities.