In the context of photosynthesis, what is the primary role of solar energy when it is absorbed by chlorophyll in plant cells?

• A. It excites electrons, initiating the light-dependent reactions.
• B. It heats the chloroplast, increasing the rate of cellular respiration.
• C. It directly converts water into glucose.
• D. It causes the plant to release oxygen by breaking down carbon dioxide.

Answer: (A)

Verified step by step guidance

1. Understand the process of photosynthesis: Photosynthesis is divided into two main stages—light-dependent reactions and light-independent reactions (Calvin cycle). The light-dependent reactions occur in the thylakoid membranes of chloroplasts and require sunlight.
2. Recognize the role of chlorophyll: Chlorophyll is a pigment in plant cells that absorbs solar energy, primarily in the blue and red wavelengths, and reflects green light. This absorption of energy is crucial for initiating the light-dependent reactions.
3. Explain the excitation of electrons: When chlorophyll absorbs solar energy, the energy excites electrons in the chlorophyll molecule, raising them to a higher energy state. This is the first step in the light-dependent reactions.
4. Describe the chain of events following electron excitation: The excited electrons are transferred to the electron transport chain, where their energy is used to produce ATP and NADPH, which are essential for the light-independent reactions.
5. Clarify why the other options are incorrect: Solar energy does not directly heat the chloroplast, convert water into glucose, or break down carbon dioxide. Instead, it excites electrons, which drive the processes that ultimately lead to glucose production and oxygen release.