What gas is released during the water splitting at PSII?

Prepare for the Leaving Certificate Photosynthesis exam. Use flashcards and multiple choice questions with hints and explanations. Ace your exam!

Multiple Choice

What gas is released during the water splitting at PSII?

Explanation:
The key idea is that the oxygen-evolving complex at PSII uses light energy to split water into electrons, protons, and oxygen. The gas released in this water-splitting step is molecular oxygen, O2. The overall reaction is 2 H2O → O2 + 4 H+ + 4 e−, so oxygen gas is produced and exits the plant cells. The other outcomes aren’t released here: hydrogen isn’t emitted as H2 in this process (the protons go into a gradient for ATP synthesis rather than as a separate gas), carbon dioxide is fixed later in the Calvin cycle, and nitrogen isn’t involved in this reaction.

The key idea is that the oxygen-evolving complex at PSII uses light energy to split water into electrons, protons, and oxygen. The gas released in this water-splitting step is molecular oxygen, O2. The overall reaction is 2 H2O → O2 + 4 H+ + 4 e−, so oxygen gas is produced and exits the plant cells. The other outcomes aren’t released here: hydrogen isn’t emitted as H2 in this process (the protons go into a gradient for ATP synthesis rather than as a separate gas), carbon dioxide is fixed later in the Calvin cycle, and nitrogen isn’t involved in this reaction.

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