Advanced Placement (AP) Biology Practice Exam

What does thermal energy refer to in biological systems?

1. Energy in motion

2. Energy from sunlight

3. Energy associated with random atomic movement

4. Stored energy in complex molecules

The correct answer is: Energy associated with random atomic movement

Thermal energy in biological systems specifically refers to the energy associated with the random motion of atoms and molecules. In any system, as temperature increases, the atoms and molecules within that system move more rapidly. This kinetic energy of the particles contributes to the overall thermal energy. In biological contexts, thermal energy plays a critical role in processes such as enzyme kinetics, where the temperature can influence the speed of reactions. Higher thermal energy can increase molecular collisions, thereby impacting reaction rates essential for life processes. Understanding that thermal energy is related to the random motion of particles helps clarify how temperature impacts biochemical reactions and physiological processes in living organisms. This concept is foundational in thermodynamics as it applies to biology, influencing everything from metabolic rates to evolutionary adaptations in various environments.