Oxygen-evolving complex

Definition

The oxygen-evolving complex (OEC) is a crucial component of photosynthesis, specifically within the photosystem II (PSII) complex, responsible for the photolysis of water molecules to release oxygen. This complex plays an essential role in converting light energy into chemical energy by facilitating the transfer of electrons derived from water, which is then used in the production of ATP and NADPH during the light-dependent reactions.

5 Must Know Facts For Your Next Test

1. The OEC contains a cluster of manganese ions that are crucial for catalyzing the water-splitting reaction.
2. In the process of water splitting, two water molecules are used to produce one molecule of oxygen, releasing four protons and four electrons.
3. The oxygen released by the OEC is a byproduct of photosynthesis and is vital for aerobic life on Earth.
4. The OEC operates through a series of oxidation states, which allows it to sequentially extract electrons from water molecules.
5. Mutations or disruptions in the OEC can significantly impair the efficiency of photosynthesis and reduce plant growth.

Review Questions

• How does the oxygen-evolving complex contribute to the overall process of photosynthesis?
  • The oxygen-evolving complex is integral to photosynthesis as it facilitates the photolysis of water, producing oxygen as a byproduct. By splitting water molecules into oxygen, protons, and electrons, the OEC provides the necessary electrons that are transferred to photosystem II. This process not only generates oxygen but also helps maintain the electron flow needed for ATP and NADPH synthesis during the light-dependent reactions.
• What role do manganese ions play within the oxygen-evolving complex?
  • Manganese ions in the oxygen-evolving complex are critical for catalyzing the water-splitting reaction during photosynthesis. These ions participate in a series of oxidation states that allow for the sequential removal of electrons from water molecules. This step is essential for facilitating electron transfer to photosystem II, ultimately contributing to energy production in plants.
• Evaluate how disruptions to the function of the oxygen-evolving complex could impact plant survival and ecosystems.
  • Disruptions to the oxygen-evolving complex can lead to significant impairments in photosynthesis, ultimately affecting plant growth and survival. If the OEC is unable to efficiently split water and release oxygen, plants would struggle to produce ATP and NADPH necessary for their metabolic processes. Such deficiencies could ripple through ecosystems, reducing plant biomass, altering food chains, and impacting organisms that rely on plants for oxygen and nutrients.

Related terms

Photosystem II: A protein-pigment complex in the thylakoid membrane that captures light energy and initiates the process of photosynthesis, particularly in the splitting of water.

Photolysis: The process by which light energy breaks down molecules, specifically the splitting of water into oxygen, protons, and electrons in photosynthesis.

Chlorophyll:

The green pigment found in plants and algae that absorbs light energy used in photosynthesis, mainly in the chloroplasts.