Splitting of Water
The photolysis of water molecules associated with PSII, releasing electrons, protons, and molecular oxygen.
What is Splitting of Water?
The breakdown of molecules by light energy.
Key formula / rule: Splitting of Water (Photolysis)
Key points
- Explain the process of water splitting (photolysis).
- Identify the location where photolysis occurs.
- Describe the role of the oxygen-evolving complex.
- List the products of water splitting and their fate.
Common exam trap
Confusing the source of oxygen in photosynthesis (mistaking it to be CO2).
Definitions
- Term
Photolysis
- Meaning
The breakdown of molecules by light energy.
- Term
Oxygen-Evolving Complex (OEC)
- Meaning
A multi-subunit protein complex associated with Photosystem II that catalyzes the oxidation of water.
- Term
Thylakoid Lumen
- Meaning
The internal space within a thylakoid membrane, where protons accumulate during photosynthesis.
Learning objectives
Explain the process of water splitting (photolysis).
Identify the location where photolysis occurs.
Describe the role of the oxygen-evolving complex.
List the products of water splitting and their fate.
Understand the significance of photolysis for photosynthesis and life on Earth.
Formulae
- Name
Splitting of Water (Photolysis)
- Note
This equation represents the net outcome of water splitting, providing electrons and protons for the light reactions and releasing oxygen.
- Expression
2H₂O → 4H⁺ + 4e⁻ + O₂
Prerequisites
Photosynthesis: An Overview
Light-Dependent Reactions of Photosynthesis
Photosystems (PSI and PSII)
Electron Transport Chain
Common mistakes
Confusing the source of oxygen in photosynthesis (mistaking it to be CO2).
Not understanding the location of photolysis (thylakoid lumen).
Forgetting the role of PSII in initiating the process.
Not recognizing the contribution of protons to the proton gradient.
Keywords
Photosynthesis
Light-Dependent Reactions
Photosystem II (PSII)
Photolysis
Splitting of Water
Oxygen-Evolving Complex (OEC)
Thylakoid Lumen
Electron Transport Chain
Proton Gradient
ATP Synthesis
Oxygen Production
Practice preview
Which of the following is NOT a product of the photolysis of water?…
easy
The splitting of water occurs in association with which photosystem?…
easy
The overall equation for the photolysis of water is often represented as: 2H2O → 4H+ + 4e- + O2. What is the significance of the protons (H+) released during this process?…
medium