Photosynthesis: Difference between revisions
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Generically, in the biological process of '''photosynthesis''', | Generically, in the biological process of '''photosynthesis''', a large number of [[Organism|organisms]] (e.g., [[Plants|plants]], [[Algae|algae]] and particular [[Bacteria|bacteria]]) capture the [[Energy|energy]] of [[Photon|photons]] in sunlight, transforming that radiant energy into biochemical energy-rich molecules, through a series of physico-chemical reactions with the starting materials, water and carbon dioxide, often abundant in their environment — the photosynthesizing [[Organism|organisms]], and the organisms that feed on them, using those energy-rich molecules as substrate and energy source, enabling the cellular functions that maintains nearly every living system on Earth in the [[Life|living]] state. | ||
Inasmuch as the [[Etymology|etymological]] definition of photosynthesis, "synthesis with light", can apply to other light generating phenomena outside biology, a leading researcher in photosynthesis, [[Robert E. Blankenship|Robert E. Blankenship]], in the Department of Chemistry and Biochemistry at [[Arizona State University|Arizona State University]], suggests this succinct definition of photosynthesis: | Inasmuch as the [[Etymology|etymological]] definition of photosynthesis, "synthesis with light", can apply to other light generating phenomena outside biology, a leading researcher in photosynthesis, [[Robert E. Blankenship|Robert E. Blankenship]], in the Department of Chemistry and Biochemistry at [[Arizona State University|Arizona State University]], suggests this succinct core definition of photosynthesis: | ||
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''Nearly'' all [[Systems biology|living systems]] on Earth depend directly or indirectly on photosynthesis (see below), and for us humans it indirectly provides essentially all of our food-energy, as well the bulk of our non-food energy resources, inasmuch as ancient photosynthesizing organisms produced the [[Fossil fuels|fossil fuels]] | ''Nearly'' all [[Systems biology|living systems]] on Earth depend directly or indirectly on photosynthesis (see below), and for us humans it indirectly provides essentially all of our food-energy, as well the bulk of our non-food energy resources, inasmuch as ancient photosynthesizing organisms produced the energy-rich carbon-containing molecules we combust as [[Fossil fuels|fossil fuels — oil, natural gas]] to generate electricity and other forms of energy we use to support human activity. | ||
In the biological process of photosynthesis in green plants, the leaves capture energy from photons in sunlight | In the biological process of photosynthesis in green plants, the leaves capture energy from photons in sunlight, using it to energize electrons, that captured and transformed energy as the essential primary energy source to drive a set of biochemical reactions that converts [[Carbon dioxide|carbon dioxide]] (CO<sub>2</sub>) and [[Water|water]] (H<sub>2</sub>O) to a [[Carbohydrate|carbohydrate]] compound, a [[triose]], a 3-carbon sugar, and a largely 'waste' product, [[Oxygen|oxygen]] (O<sub>2</sub>) — thus defining 'oxygenic' photosynthesis.<ref>'''<u>Note:</u>''' Summary equations typically depict [[Glucose|glucose]] as the carbohydrate end-product of photosynthesis, whereas photosynthesizing cells generate very little glucose per se; the three-carbon trioses represent the more immediate photosynthetic carbohydrate.</ref>. Triose, as triose phosphates, exit the leaf cell's [[Organelle|organelles]] that synthesizes them — viz., a [[Chloroplat|chloroplast]], condense themselves into six-carbon [[Hexose|hexose]] phosphates, ultimately forming [Dimer|dimers]] like sucrose, or [[Polymer|polymers]] like [[Starch|starch]] or [[Cellulose|cellulose]], the so-called ''[[Redox|reduced]'' forms of carbon, reduced in the sense of enrichment in the electrons energized by the captured photons, thus forming of energy-rich carbon compounds that, as mentioned, the photosynthesizing organisms and their predators need to perform the cellular work that maintains them in the [[Life|living]] state. | ||
The photosynthetic process effectively stores energy in a variety of energy-rich molecules the photosynthetic organism can [[Metabolism|metabolize]] to generate [[Adenosine triphosphate|adenosine triphosphate]] ([[ATP|ATP]]), the universal circulating and recyclable energy currency of cells, so-called because it can provide the energy needed to drive many of the biochemical reactions necessary to synthesize the macromolecules and molecular intermediates required to maintain the cell in a living state. The process also produces other recyclable forms of circulating energy currency (e.g., [[NADPH|NADPH]]). Photosynthesizing cells thus convert light energy to the life-sustaining chemical energy that drives life-sustaining cellular processes, to paraphrase the words of Professor Blankenship quoted above. | |||
Organisms that photosynthesize function as [[Autotroph|autotrophs]] — viz., organisms that generate their own source of food-energy — specifically referred to as [[Photoautotoph|photoautotrophs]]. They draw on minerals and other inorganic compounds from the environment and produce an ultimately photon-energy-derived complement of carbohydrates, proteins and lipids that self-organize the photoautotophic organism. In doing so they directly, though blindly, offer themselves as a source of food-energy (e.g., as vegetables, fruits) for consumption by us humans and other organisms, so-called [[Heterotroph|heterotrophs]] — viz., organisms that feed on other organisms or on their energy-rich structural components — and indirectly provide a source of food-energy in the form of the non-human heterotrophs that we humans consume (e.g., chicken, fish and other animals). Photosynthesizing cells also supply the sufficient amounts of oxygen they and we need to generate ATP and NADPH, and they consume the 'waste' CO<sub>2</sub> produced in the process of generating ATP. | Organisms that photosynthesize function as [[Autotroph|autotrophs]] — viz., organisms that generate their own source of food-energy — specifically referred to as [[Photoautotoph|photoautotrophs]]. They draw on minerals and other inorganic compounds from the environment and produce an ultimately photon-energy-derived complement of carbohydrates, proteins and lipids that self-organize the photoautotophic organism. In doing so they directly, though blindly, offer themselves as a source of food-energy (e.g., as vegetables, fruits) for consumption by us humans and other organisms, so-called [[Heterotroph|heterotrophs]] — viz., organisms that feed on other organisms or on their energy-rich structural components — and indirectly provide a source of food-energy in the form of the non-human heterotrophs that we humans consume (e.g., chicken, fish and other animals). Photosynthesizing cells also supply the sufficient amounts of oxygen they and we need to generate ATP and NADPH, and they consume the 'waste' CO<sub>2</sub> produced in the process of generating ATP. | ||
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Not all photosynthesizing organisms produce oxygen. The specific physico-chemical reactions of those that do biologists refer to as oxygenic photosynthesis, and those that do not as 'anoxygenic' photosynthesis. Oxygenic photosynthesis accounts for most of the oxygen in the atmosphere. | Not all photosynthesizing organisms produce oxygen. The specific physico-chemical reactions of those that do biologists refer to as oxygenic photosynthesis, and those that do not as 'anoxygenic' photosynthesis. Oxygenic photosynthesis accounts for most of the oxygen in the atmosphere. | ||
This article will classify the differing types of photosynthesizing organisms, and describe the details of the differing photosynthetic mechanisms employed by them. It will also discuss the implications of photosynthesis in the sciences of biology, geology, oceanography, climatology, and other areas of importance to the life of planet Earth. | This article will classify the differing types of photosynthesizing organisms, and describe the details of the differing photosynthetic mechanisms employed by them. It will also discuss the implications of photosynthesis in the sciences of biology, geology, oceanography, climatology, and other areas of importance to the life of planet Earth, since without photosynthesis nearly every species on Earth would perish. | ||
Preliminarily, the reader might refer to the following: <ref name=Blankenship02/> <ref>Farabee MJ. (2007) [http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html#What%20is%20Photosynthesis? What is photosynthesis?] [http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html Online Biology Book] | Preliminarily, the reader might refer to the following: <ref name=Blankenship02/> <ref>Farabee MJ. (2007) [http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html#What%20is%20Photosynthesis? What is photosynthesis?] [http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookTOC.html Online Biology Book] | ||
Revision as of 16:01, 20 February 2009
Generically, in the biological process of photosynthesis, a large number of organisms (e.g., plants, algae and particular bacteria) capture the energy of photons in sunlight, transforming that radiant energy into biochemical energy-rich molecules, through a series of physico-chemical reactions with the starting materials, water and carbon dioxide, often abundant in their environment — the photosynthesizing organisms, and the organisms that feed on them, using those energy-rich molecules as substrate and energy source, enabling the cellular functions that maintains nearly every living system on Earth in the living state.
Inasmuch as the etymological definition of photosynthesis, "synthesis with light", can apply to other light generating phenomena outside biology, a leading researcher in photosynthesis, Robert E. Blankenship, in the Department of Chemistry and Biochemistry at Arizona State University, suggests this succinct core definition of photosynthesis:
|
Photosynthesis is a process in which light energy is captured and stored by an organism, and the stored energy is used to drive cellular processes. [1] |
Nearly all living systems on Earth depend directly or indirectly on photosynthesis (see below), and for us humans it indirectly provides essentially all of our food-energy, as well the bulk of our non-food energy resources, inasmuch as ancient photosynthesizing organisms produced the energy-rich carbon-containing molecules we combust as fossil fuels — oil, natural gas to generate electricity and other forms of energy we use to support human activity.
In the biological process of photosynthesis in green plants, the leaves capture energy from photons in sunlight, using it to energize electrons, that captured and transformed energy as the essential primary energy source to drive a set of biochemical reactions that converts carbon dioxide (CO2) and water (H2O) to a carbohydrate compound, a triose, a 3-carbon sugar, and a largely 'waste' product, oxygen (O2) — thus defining 'oxygenic' photosynthesis.[2]. Triose, as triose phosphates, exit the leaf cell's organelles that synthesizes them — viz., a chloroplast, condense themselves into six-carbon hexose phosphates, ultimately forming [Dimer|dimers]] like sucrose, or polymers like starch or cellulose, the so-called [[Redox|reduced] forms of carbon, reduced in the sense of enrichment in the electrons energized by the captured photons, thus forming of energy-rich carbon compounds that, as mentioned, the photosynthesizing organisms and their predators need to perform the cellular work that maintains them in the living state.
The photosynthetic process effectively stores energy in a variety of energy-rich molecules the photosynthetic organism can metabolize to generate adenosine triphosphate (ATP), the universal circulating and recyclable energy currency of cells, so-called because it can provide the energy needed to drive many of the biochemical reactions necessary to synthesize the macromolecules and molecular intermediates required to maintain the cell in a living state. The process also produces other recyclable forms of circulating energy currency (e.g., NADPH). Photosynthesizing cells thus convert light energy to the life-sustaining chemical energy that drives life-sustaining cellular processes, to paraphrase the words of Professor Blankenship quoted above.
Organisms that photosynthesize function as autotrophs — viz., organisms that generate their own source of food-energy — specifically referred to as photoautotrophs. They draw on minerals and other inorganic compounds from the environment and produce an ultimately photon-energy-derived complement of carbohydrates, proteins and lipids that self-organize the photoautotophic organism. In doing so they directly, though blindly, offer themselves as a source of food-energy (e.g., as vegetables, fruits) for consumption by us humans and other organisms, so-called heterotrophs — viz., organisms that feed on other organisms or on their energy-rich structural components — and indirectly provide a source of food-energy in the form of the non-human heterotrophs that we humans consume (e.g., chicken, fish and other animals). Photosynthesizing cells also supply the sufficient amounts of oxygen they and we need to generate ATP and NADPH, and they consume the 'waste' CO2 produced in the process of generating ATP.
Not all photosynthesizing organisms produce oxygen. The specific physico-chemical reactions of those that do biologists refer to as oxygenic photosynthesis, and those that do not as 'anoxygenic' photosynthesis. Oxygenic photosynthesis accounts for most of the oxygen in the atmosphere.
This article will classify the differing types of photosynthesizing organisms, and describe the details of the differing photosynthetic mechanisms employed by them. It will also discuss the implications of photosynthesis in the sciences of biology, geology, oceanography, climatology, and other areas of importance to the life of planet Earth, since without photosynthesis nearly every species on Earth would perish.
Preliminarily, the reader might refer to the following: [1] [3] [4] [5] [6] [7] [8] [9]
References Cited and Notes in Text
- ↑ 1.0 1.1 Blankenship RE. (2002) Molecular Mechanisms of Photosynthesis. Wiley-Blackwell. ISBN 0632043210 (ISBN-10); ISBN 978-0632043217 (ISBN-13) (pbk)
- Table of Contents:
- Preface
- Acknowledgments
- The Basic Principles of Photosynthetic Energy Storage
- Photosynthetic Organisms and Organelles
- History and Early Development of Photosynthesis
- Photosynthetic Pigments: Structure and Spectroscopy
- Antenna Complexes and Energy Transfer Processes
- Reaction Center Complexes
- Electron Transfer Pathways and Components
- Chemiosmotic Coupling and ATP Synthesis
- Carbon Metabolism
- Genetics, Assembly and Regulation of Photosynthetic Systems
- Origin and Evolution of Photosynthesis
- Light, Energy and Kinetics
- Index
- ↑ Note: Summary equations typically depict glucose as the carbohydrate end-product of photosynthesis, whereas photosynthesizing cells generate very little glucose per se; the three-carbon trioses represent the more immediate photosynthetic carbohydrate.
- ↑ Farabee MJ. (2007) What is photosynthesis? Online Biology Book
- Detailed teatment of photosynthesis in an online biology course textbook. Includes an illustrated glossary.
- ↑ Photosynthesis Encyclopedia Britannica Free Full-Text Article
- ↑ John Whitmarsh, Govindjee. THE PHOTOSYNTHETIC PROCESS In: "Concepts in Photobiology: Photosynthesis and Photomorphogenesis", Edited by GS Singhal, G Renger, SK Sopory, K-D Irrgang and Govindjee, Narosa Publishers/New Delhi; and Kluwer Academic/Dordrecht, pp. 11-51. The online text is a revised and modified version of "Photosynthesis" by J. Whitmarsh and Govindjee (1995), published in Encyclopedia of Applied Physics (Vol. 13, pp. 513-532) by VCH Publishers, Inc.
- A comprehensive treatment of photosynthesis in a book chapter online. Includes history and research aspects. Detailed.
- ↑ Vermaas W. Introduction to Photosynthesis and Its Applications
- An introduction to photosynthesis readily accessible to the general reader.
- ↑ Raven PH, Evert RF, Eichhorn SE. (1999) Photosynthesis, Light, and Life. Chapter 7. In: Biology of Plants. 6th ed. New York: W.H. Freeman. ISBN 1-57259-041-6; ISBN 1-57259-611-2 (comp).
- ↑ Kiang, NC, Siefert J, Govindjee, Blankenship RE. (2007) Special Paper. Spectral Signatures of Photosynthesis. I. Review of Earth Organisms. Astrobiology 7:222-251.
- ’’’From the Abstract:’’’ We provide (1) a brief review of how photosynthesis works, (2) an overview of the diversity of photosynthetic organisms, their light harvesting systems, and environmental ranges, (3) a synthesis of photosynthetic surface spectral signatures, and (4) evolutionary rationales for photosynthetic surface reflectance spectra with regard to utilization of photon energy and the planetary light environment.
- ↑ Cite error: Invalid
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