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Related Experiment Videos

Photosynthesis and negative entropy production.

Robert C Jennings1, Enrico Engelmann, Flavio Garlaschi

  • 1Istituto di Biofisica del Consiglio Nazionale delle Ricerche-Sezione di Milano, Dipartimento di Biologia, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy. robert.jennings@unimi.it

Biochimica Et Biophysica Acta
|September 6, 2005
PubMed
Summary

The Carnot cycle efficiency for photosynthetic pigment systems is inaccurate. New thermodynamic analysis reveals higher efficiencies for Photosystem I and II, operating with negative entropy production.

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Area of Science:

  • Photosynthesis research
  • Thermodynamics
  • Biophysics

Background:

  • The Carnot cycle is commonly used to estimate maximum photosynthetic efficiency.
  • This model assumes energy transfer from radiation (hot bath) to pigment systems (cold bath).
  • Previous models overlook microscopic entropy changes in photon absorption and photochemistry.

Purpose of the Study:

  • Critically examine the applicability of the Carnot cycle to photosynthetic efficiency.
  • Investigate entropy changes at the single photosystem level.
  • Determine the thermodynamic efficiency of Photosystem I and Photosystem II.

Main Methods:

  • Analysis of entropy changes during photon absorption and excited state relaxation.
  • Thermodynamic modeling of primary photochemistry in single photosystems.

Related Experiment Videos

  • Application of principles to isolated Photosystem I and Photosystem II cores.

    • Main Results:

    • Carnot cycle efficiency is inaccurate for photosynthetic pigment systems.
    • Entropy losses from excited state generation are minimal.
    • Photosystem I and Photosystem II exhibit high thermodynamic efficiencies (>0.98 and >0.92, respectively).
    • These photosystems can operate with negative entropy production.

    Conclusions:

    • Photosynthetic efficiency is not accurately described by the Carnot cycle alone.
    • Microscopic entropy changes are crucial for understanding photosynthetic energy transfer.
    • Photosystem I and Photosystem II operate thermodynamically efficiently, potentially with negative entropy production.