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13 - Biochemical and molecular techniques for the study of photosynthetic processes
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Book:
- Terrestrial Photosynthesis in a Changing Environment
- Published online:
- 05 March 2013
- Print publication:
- 19 July 2012, pp 186-205
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Summary
Introduction
Increasing understanding of the many molecular and biochemical processes that respond in a purposive way to the changing environment has given rise to an appreciation that many, if not all, environmental cues evoke primary responses at a molecular level, and that it is these responses that result in changes in gross plant physiology and morphology. Likewise, changes in the relative proportions of metabolites and ions within intracellular compartments in response to such environmental cues also give rise to multiple changes in gene expression. The interaction between these levels of complexity in response to changes in the external environment is illustrated in Scheme 13.1.
This chapter describes and discusses approaches: (1) for the unbiased analyses of gene, protein and metabolite function facilitated by a variety of high-throughput approaches; and (2) for the focused analyses of specific genes, gene products and metabolites. The former approaches seek to identify hitherto unknown genes and molecular interactions, while the latter are used to probe those elements that we currently consider most important in understanding and interpreting how photosynthetic processes relate to ecophysiological questions. In particular, we discuss aspects of the isolation and assay of the carboxylating enzymes, Rubisco and phosphorenolpyruvate carboxylase (PEPC), owing to their pivotal roles in assimilation and to the continuing interest in their measurement. In general, we have selected methods and approaches that have been applied in our laboratories, but acknowledge that many alternative methods could have been described, which are equally reliable and quantitative.
2 - Biochemistry and photochemistry of terrestrial photosynthesis: a synopsis
- Edited by Jaume Flexas, Universitat de les Illes Balears, Palma de Mallorca, Francesco Loreto, Hipólito Medrano, Universitat de les Illes Balears, Palma de Mallorca
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- Book:
- Terrestrial Photosynthesis in a Changing Environment
- Published online:
- 05 March 2013
- Print publication:
- 19 July 2012, pp 9-19
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Summary
Introduction
Photosynthesis is typically understood as the light-dependent production of sugar from carbon dioxide (CO2). The endosymbiotic chloroplast is the cellular location for most of this metabolism in plants, but some additional metabolism occurs in the cytosol to make the sugars that will be transported around the plant, mainly sucrose and also sugar alcohols, such as sorbitol and manitol. There are many processes that can properly be called photosynthesis, but a core set of processes underlie most of the considerations in this book. This chapter will provide an overview of those processes, and many topics covered in this chapter are the subject of more in-depth chapters later on. This chapter begins by describing the initial capture and temporary storage of light energy as highly reactive molecules (nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP)) on carbon. By reducing (i.e., by adding electrons to) carbon from its most oxidised state (CO2) to the status of sugars (CH2O)n, the energy initially stored as NADPH and ATP can be stored on the carbon. Additional energy can be stored on each carbon atom by reducing it fully, as happens in the synthesis of oils (R-CH2-R), but this is generally not considered when describing photosynthesis. Finally, issues surrounding uptake of the CO2 will be addressed.
Photochemistry Synopsis
Photochemistry, the capture of light energy and its conversion to chemical energy suitable for reducing CO2 to sugar, is the source of nearly all energy available to living things. Energy captured by absorbing molecules is stored as the high-energy intermediates NADPH (reducing power) and ATP (sometimes called the energy currency of the cell).