What substance is split into electrons, oxygen and protons during photosynthesis?

What substance is split into electrons, oxygen and protons during photosynthesis?

• A. Carbon dioxide
• B. Glucose
• C. Nitrogen
• D. Water

Answer: (D)

The key idea is that the light-dependent reactions split a molecule to supply the electrons and protons needed for the electron transport chain, with oxygen released as a byproduct. In photosynthesis, water is split by the oxygen-evolving complex in photosystem II during photolysis. This reaction provides electrons to replace those excited by light, releases protons to help build the proton gradient, and releases oxygen gas. The energized electrons flow through the electron transport chain, driving the formation of ATP and NADPH that fuel the later Calvin cycle to make sugars. Carbon dioxide is used later to build sugars, not to supply electrons in this stage, while glucose is the sugar produced later, and nitrogen isn’t involved in this splitting process. Therefore, water is the substance that is split into electrons, oxygen, and protons during photosynthesis.

The key idea is that the light-dependent reactions split a molecule to supply the electrons and protons needed for the electron transport chain, with oxygen released as a byproduct. In photosynthesis, water is split by the oxygen-evolving complex in photosystem II during photolysis. This reaction provides electrons to replace those excited by light, releases protons to help build the proton gradient, and releases oxygen gas. The energized electrons flow through the electron transport chain, driving the formation of ATP and NADPH that fuel the later Calvin cycle to make sugars. Carbon dioxide is used later to build sugars, not to supply electrons in this stage, while glucose is the sugar produced later, and nitrogen isn’t involved in this splitting process. Therefore, water is the substance that is split into electrons, oxygen, and protons during photosynthesis.