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Studying the Supramolecular Organization of Photosynthetic Membranes within Freeze-fractured Leaf Tissues by Cryo-scanning Electron Microscopy
Published on: June 23, 2016
Structure and function of photosystems I and II
Nathan Nelson1, Charles F Yocum
1Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel. nelson@post.tau.ac.il
Annual Review of Plant Biology
|May 4, 2006
Summary
Oxygenic photosynthesis, driven by photosystem I and photosystem II, converts sunlight into chemical energy. Recent structural studies reveal the intricate architecture and evolutionary history of these vital membrane protein complexes.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Oxygenic photosynthesis is the primary process for converting solar energy into chemical energy.
- Four key membrane-protein complexes catalyze this process: photosystem I (PSI), photosystem II (PSII), cytochrome b(6)f, and F-ATPase.
- PSI and PSII play crucial roles in generating redox potentials essential for life and water oxidation, respectively.
Purpose of the Study:
- To elucidate the structure and function of photosystem I and photosystem II.
- To understand the evolutionary forces that have shaped oxygenic photosynthesis.
- To provide insights into the architecture and mechanism of these complex membrane proteins.
Main Methods:
- Spectroscopy
- Molecular genetics
- Biochemistry
- Structural analysis of PSI and PSII from various organisms
Main Results:
- New structural data for PSI and PSII have been obtained.
- These structures illuminate the detailed architecture and operational mechanisms of the photosystems.
- The findings offer insights into the evolutionary pathways of oxygenic photosynthesis.
Conclusions:
- The study enhances our understanding of the fundamental process of oxygenic photosynthesis.
- Structural insights into PSI and PSII reveal their complex mechanisms and evolutionary adaptations.
- This research contributes to the broader knowledge of energy conversion in biological systems.
Related Concept Videos
01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:22Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:32Photosystems
Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in the membrane of tiny sac-like structures called thylakoids placed inside the chloroplast.
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:29The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
01:26Oxygenic Photosynthesis
Oxygenic photosynthesis is a fundamental process in which light energy is harnessed to drive the oxidation of water, leading to the production of molecular oxygen (O₂), adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide phosphate (NADPH). This process is essential for sustaining aerobic life on Earth and is primarily carried out by cyanobacteria, algae, and plants. The core of oxygenic photosynthesis lies in the thylakoid membranes, where chlorophyll pigments facilitate light...
01:15The Antenna Complex
Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - the main site of photochemical reactions as well as in the antenna complex. Under average light conditions, the rate at which reaction center pigments absorb light is far below the electron transport chain's capacity. As a result, the reaction center alone cannot provide enough energy to drive photosynthesis. The photosynthetic efficiency can...