When chloroplast pigments absorb light, _____.

• A. they immediately release oxygen gas
• B. ATP is directly synthesized from glucose
• C. carbon dioxide is fixed into organic molecules
• D. their electrons become excited to a higher energy state

Answer: (D)

Verified step by step guidance

1. Understand the role of chloroplast pigments: Chloroplast pigments, such as chlorophyll, are specialized molecules that absorb light energy during photosynthesis. Their primary function is to capture light energy and initiate the process of energy conversion.
2. Recognize the concept of electron excitation: When chloroplast pigments absorb light, the energy from the photons excites electrons within the pigment molecules. This means the electrons gain energy and move to a higher energy state.
3. Clarify why oxygen gas is not immediately released: Oxygen gas is released during the light-dependent reactions of photosynthesis, specifically during the splitting of water molecules (photolysis). This occurs later in the process, not directly as a result of pigment excitation.
4. Explain why ATP is not directly synthesized from glucose: ATP is synthesized during the light-dependent reactions of photosynthesis through a process called photophosphorylation. Glucose is produced later during the Calvin cycle, which is part of the light-independent reactions.
5. Highlight the correct process: The excitation of electrons in chloroplast pigments is the first step in the light-dependent reactions. These excited electrons are transferred to the electron transport chain, where their energy is used to produce ATP and NADPH, which are essential for the Calvin cycle to fix carbon dioxide into organic molecules.