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Biological Systems and the Environment · Semester 2

Non-Cyclic Photophosphorylation: Photosystem II, Z-Scheme Electron Flow, and Oxygen Evolution

Students will investigate how energy flows through ecosystems, constructing food chains and food webs to illustrate trophic levels.

Key Questions

  1. Explain the sequence of events in non-cyclic photophosphorylation from the photoactivation of P680 in PSII through electron transport to PSI, including the oxidative splitting of water, plastoquinone reduction, and chemiosmotic ATP synthesis.
  2. Analyse the role of plastocyanin and ferredoxin in electron transfer between PSII and PSI, and explain how the Z-scheme accounts for the thermodynamics of electron flow from water to NADP⁺.
  3. Evaluate the experimental evidence — including the wavelength-dependence of O₂ evolution and the Emerson enhancement effect — that demonstrates the necessity of two photosystems operating in series rather than a single photosystem.

MOE Syllabus Outcomes

MOE: Energy and Organisms - MS
Level: JC 1
Subject: Biology
Unit: Biological Systems and the Environment
Period: Semester 2

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