Advanced Placement (AP) Biology Practice Exam

Which of the following best describes light energy?

1. Stored energy from chemical bonds

2. Energy that is used for mechanical work

3. Energy from the sun converted during photosynthesis

4. Potential energy associated with physical changes

The correct answer is: Energy from the sun converted during photosynthesis

Light energy refers to the energy carried by electromagnetic waves, particularly those within the visible spectrum. In the context of photosynthesis, light energy is captured by plants using chlorophyll, a pigment that absorbs sunlight. This energy is then converted into chemical energy through a series of reactions that produce glucose and oxygen from carbon dioxide and water. This process is essential for life on Earth, as it provides the energy that fuels the growth of plants and, subsequently, other organisms in the food chain. The other options describe different types of energy. For example, stored energy from chemical bonds refers to potential energy found in molecules, which is released during chemical reactions but does not pertain specifically to light. Energy used for mechanical work relates to kinetic energy that can cause movement, while potential energy associated with physical changes describes stored energy in systems that can be converted to kinetic energy but is unrelated to the nature of light energy itself. Thus, the option that best aligns with the definition and role of light energy is the one that involves its conversion during photosynthesis.