Biological Sciences
Photosynthesis
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process occurs in the chloroplasts of plant cells and involves the absorption of light by chlorophyll, which drives the synthesis of organic compounds from carbon dioxide and water. Overall, photosynthesis is essential for the production of oxygen and food in the biosphere.
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10 Key excerpts on "Photosynthesis"
eBook - PDF- Mary D Archer, James Barber(Authors)
- 2004(Publication Date)
- ICP(Publisher)
CHAPTER 1 Photosynthesis AND PHOTOCONVERSION MARY D. ARCHER Centre for Energy Policy and Technology, Imperial College London SW7 2AZ, UK mda 12 @cam. ac. uk and JAMES BARBER Wolfson Laboratories, Department of Biological Sciences, South Kensington Campus, Imperial College London SW7 2AZ, UK j . barber @ imperial.ac. uk Nature set herself the task of capturing the lightjlooding toward the earth and of storing this, the most elusive of all forces, by converting it into an immobile force ... the plant world const- itutes a reservoir in which the jleeting sun rays are fixed and ingeniously stored for future use, a providential measure to which the very existence of the human race is inescapably bound. Julius Robert Mayer, The Organic Motion in its Relation to Metabolism, 1845. 1.1 Introduction The word Photosynthesis means ‘building up by light’, and the process is the building up, by plants, algae and certain bacteria under the action of sunlight, of organic compounds (mainly carbohydrates) from two very simple inorganic molecules, water (HzO) and carbon dioxide ((202). Put another way, Photosynthesis is the light-driven reduction of atmospheric carbon dioxide by water to energy-rich organic compounds. But this reductionist, chemist’s view gives little hint of the central role of photo- synthesis in sustaining life on Earth. Photosynthesis is the primary engine of the biosphere, essential to life since it is almost the sole process by which the chemical energy to maintain living organisms is made. It provides all our food, either directly in the form of green plants or indirectly in the form of animals that eat green plants or other animals that have eaten green plants. The only living organisms not sustained directly or indirectly by Photosynthesis are the chemoautotrophs, primitive bacteria that harness the energy of inorganic compounds such as H2S to obtain the metabolic energy they need to grow and replicate, and the organisms that feed off them.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 13 Photosynthesis Composite image showing the global distribution of Photosynthesis, including both oceanic phytoplankton and vegetation Overall equation for the type of Photosynthesis that occurs in plants ________________________ WORLD TECHNOLOGIES ________________________ Photosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs , since they can create their own food. In plants, algae, and cyan-obacteria, Photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food (the exceptions are chemoautotrophs that live in rocks or around deep sea hydrothermal vents). The rate of energy capture by Photosynthesis is immense, approximately 100 terawatts, which is about six times larger than the power consumption of human civilization. As well as energy, Photosynthesis is also the source of the carbon in all the organic compounds within organisms' bodies. In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year. Although Photosynthesis can happen in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- The English Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 1 Photosynthesis Composite image showing the global distribution of Photosynthesis, including both ocea-nic phytoplankton and vegetation Overall equation for the type of Photosynthesis that occurs in plants Photosynthesis is a process that converts carbon dioxide into organic compounds, es-pecially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, ________________________ WORLD TECHNOLOGIES ________________________ and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs , since they can create their own food. In plants, algae, and cyanoba-cteria, Photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food (the exceptions are chemoautotrophs that live in rocks or around deep sea hydrothermal vents). The rate of energy capture by Photosynthesis is immense, approximately 100 terawatts, which is about six times larger than the power consumption of human civilization. As well as energy, Photosynthesis is also the source of the carbon in all the organic compounds within organisms' bodies. In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year. Although Photosynthesis can happen in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 10 Photosynthesis Composite image showing the global distribution of Photosynthesis, including both oceanic phytoplankton and vegetation Overall equation for the type of Photosynthesis that occurs in plants Photosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, ________________________ WORLD TECHNOLOGIES ________________________ and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs , since they can create their own food. In plants, algae, and cyanobacteria, Photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food (the exceptions are chemoautotrophs that live in rocks or around deep sea hydrothermal vents). The rate of energy capture by Photosynthesis is immense, approximately 100 terawatts, which is about six times larger than the power consumption of human civilization. As well as energy, Photosynthesis is also the source of the carbon in all the organic compounds within organisms' bodies. In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year. Although Photosynthesis can happen in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Research World(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 6 Photosynthesis Composite image showing the global distribution of Photosynthesis, including both oceanic phytoplankton and vegetation Overall equation for the type of Photosynthesis that occurs in plants ________________________ WORLD TECHNOLOGIES ________________________ Photosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs , since they can create their own food. In plants, algae, and cyanobacteria, Photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food (the exceptions are chemoautotrophs that live in rocks or around deep sea hydrothermal vents). The rate of energy capture by Photosynthesis is immense, approximately 100 terawatts, which is about six times larger than the power consumption of human civilization. As well as energy, Photosynthesis is also the source of the carbon in all the organic compounds within organisms' bodies. In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year. Although Photosynthesis can happen in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- The English Press(Publisher)
In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year. Although Photosynthesis can happen in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane. Some of the light energy gathered by chlorophylls is stored in the form of adenosine triphosphate (ATP). The rest of the energy is used to remove electrons from a substance such as water. These electrons are then used in the reactions that turn carbon dioxide into organic compounds. In plants, algae and cyanobacteria, this is done by a sequence of reactions called the Calvin cycle, but different sets of reactions are found in some bacteria, such as the reverse Krebs cycle in Chlorobium . Many photosynthetic organisms have adaptations that concentrate or store carbon dioxide. This helps reduce a wasteful process called photorespiration that can consume part of the sugar produced during Photosynthesis. ________________________ WORLD TECHNOLOGIES ________________________ Overview of cycle between autotrophs and heterotrophs. Photosynthesis is the main means by which plants, algae and many bacteria produce organic compounds and oxygen from carbon dioxide and water (green arrow). The first photosynthetic organisms probably evolved about 3,500 million years ago, early in the evolutionary history of life, when all forms of life on Earth were microorganisms and the atmosphere had much more carbon dioxide. They most likely used hydrogen or hydrogen sulfide as sources of electrons, rather than water. Cyanobacteria appeared later, around 3,000 million years ago, and drastically changed the Earth when they began to oxygenate the atmosphere, beginning about 2,400 million years ago.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 14 Photosynthesis Composite image showing the global distribution of Photosynthesis, including both oceanic phytoplankton and vegetation Overall equation for the type of Photosynthesis that occurs in plants ________________________ WORLD TECHNOLOGIES ________________________ Photosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs , since they can create their own food. In plants, algae, and cyanob-acteria, Photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth. As well as maintaining the normal level of oxygen in the atmosphere, nearly all life either depends on it directly as a source of energy, or indirectly as the ultimate source of the energy in their food (the exceptions are chemoautotrophs that live in rocks or around deep sea hydrothermal vents). The rate of energy capture by Photosynthesis is immense, approximately 100 terawatts, which is about six times larger than the power consumption of human civilization. As well as energy, Photosynthesis is also the source of the carbon in all the organic compounds within organisms' bodies. In all, photosynthetic organisms convert around 100–115 teragrams of carbon into biomass per year. Although Photosynthesis can happen in different ways in different species, some features are always the same. For example, the process always begins when energy from light is absorbed by proteins called photosynthetic reaction centers that contain chlorophylls. In plants, these proteins are held inside organelles called chloroplasts, while in bacteria they are embedded in the plasma membrane.
eBook - PDFPhotosynthesis V2
Development, Carbon Metabolism, and Plant Productivity
- Govindjee, Unknown Govindjee(Authors)
- 2012(Publication Date)
- Academic Press(Publisher)
Introduction to Photosynthesis: Carbon Assimilation and Plant Productivity ARCHIE R. PORTIS, JR. I. Introduction Photosynthesis is the process by which green plants, cyanobacteria, and photosynthetic bacteria produce organic matter from C 0 2 and hy-drogen donors. In green plants, this process occurs in the chloroplasts. T h e reactions begin by the conversion of light energy, H 2 0 , adenosine diphosphate (ADP), phosphate and oxidized nicotinamide adenine di-nucleotide phosphate (NADP + ) into 0 2 , adenosine triphosphate (ATP), and reduced nicotinamide adenine dinucleotide phosphate (NADPH). This aspect of Photosynthesis often called the light reactions is discussed in another volume (Govindjee, 1982). T h e utilization of the A T P and N A D P H for the conversion of C 0 2 to carbohydrates often called the dark reactions is the subject of the present volume. T h e photosynthate thus formed is translocated to various parts of the plant and utilized for its growth. In this introductory chapter, we shall introduce the reader to the various chapters dealing with both the ques-tion of C 0 2 assimilation and plant productivity. II. General Discussion T h e continuing existence of life on earth ultimately depends on the utilization of solar energy by the process known as Photosynthesis. In the higher plants, algae, and cyanobacteria, this process is usually summa-rized as representing the oxidation of water to oxygen and the concomitant re-I. Introduction II. General Discussion III. Conclusions References. 6 H 2 0 + 6 C 0 2 4 ϋ ν C 6 H 1 2 0 6 + 6 0 2 AG' S = 686 kcal 1 Photosynthesis: Development, Carbon Metabolism, and Plant Productivity, Vol. II Copyright © 1982 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN: 0-12-294302-3 1 1 1 11 11 2 ARCHIE R. PORTIS, JR. auction of carbon dioxide to carbohydrate by the use of light quanta (hv).
eBook - PDF- Jean-Claude Leclerc(Author)
- 2003(Publication Date)
- CRC Press(Publisher)
Chapter 2 Photosynthesis and Plant Production 1. INTRODUCTION Photosynthesis, a major route for the uptake of energy, is the basis for all life functions. It appeared very early on earth through photosynthetic bacteria, since the atmosphere and water did not provide organic mol ecules or minerals yielding a large quantity of energy, or in sufficient concentrations, except in particular ecosystems. Photosynthesis may be considered to have developed in two major stages. First there was formation of a photochemical system with bacterial chlorophyll, which, when it absorbs light energy, can achieve a separation of charges that allows electron activation from substances (still sufficiently abundant in the terrestrial atmosphere) having Em7 values that could be considered averages, for example H2S (S/HS~ = -0.18 V), H2 (H2/2H+ + 2e = -0.43 V (but in fact the values are closer to zero in the natural environment, because of pH and low concentration), succinic acid (close to -0.1 V), and fumaric acid (close to 0 V). Electrons activated by light energy increase their potential to about -0.5 to -0.6 V. This allows reduction of several iron-sulphur proteins, more or less linked to the membrane, such as ferredoxin, which can, in turn, reduce NAD or NADP (Em7 = -0.32 V). Such reactions provide all the reductive energy at the cell level. NADHH+ and NAD+ have a difference of free energy of around 50 kcal/mole. The activation of electrons also allows, through the crossing of the membrane, the creation of a membrane potential. Finally, the membrane quinones, which are intermediary transporters of the electrons, also transport H+ from one side of the membrane to the other. Thus, in linkage with CFQand CF1 complexes, a photophosphorylation takes place, i.e., a synthesis of ATP exploiting the proto-motor force created by the light energy. This can also be illustrated in a diagram of the photosynthetic membrane of purple non-sulphur bacteria or green non-sulphur bacteria (Fig. 2.1).
eBook - PDF- William V Dashek, Marcia Harrison(Authors)
- 2010(Publication Date)
- CRC Press(Publisher)
The major end product of Photosynthesis is glucose 6-phosphate, the predominant starting material for storage forms of chemical energy and for synthesis of cellular components. When glucose 6-phosphate is metabolized in cells, the energy that was trapped in the molecule by Photosynthesis is released to provide the energy required for synthetic reactions and growth. In contrast to animals, glucose does not occur in the free form to a significant amount in plants. Of fundamental impor- tance to the biosphere however, is the fact that plants are the primary source of the glucose unit, which they store in polymeric form. Aerobic metabolism of glucose in all organisms produces CO 2 and H 2 O. Persis- tence of life on earth would not have been possible without a means to convert these "waste products" back to glucose. Other- wise, living organisms would long ago have run out of food. Conversion of CO 2 and H 2 O PLANT CELL BIOLOGY The energy required for complete synthesis of a mole of glucose is six times that shown in eqn (1). The source of energy to drive this reaction is light. The molecular apparatus that performs this process—photosynthe- sis—is located in the "thylakoid" (Greek, "sac-like") membrane, which is confined within chloroplasts in plants. Light energy is absorbed by molecules of chlorophyll (Chi) located in this membrane. Wave- lengths of light that contain levels of energy that can be accommodated by the electronic structure of Chi, primarily in the blue and red regions of the visible spectrum (photons with energy levels around 280 and 170 kjoules per mole respectively), are absorbed and generate "excited" states of Chi. From the energy content of these useful wavelengths, it is obvious that more than one photon must be absorbed to fix one mol- ecule of CO 2 .
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