5. What
are the
the requirment of photosynthesis
Answers
Answered by
1
Answer:
To perform photosynthesis, plants need three things: carbon dioxide, water, and sunlight. for photosynthesis. ... Plants also require water to make their food. Depending on the environment, a plant's access to water will vary.
Answered by
0
This problem has been under serious study for decades because people would like to find a way to do photosynthesis artificially.
Let us define photosynthesis first. In this answer, I will narrow the general definition by considering only oxygen-producing (oxygenic) phototosynthesis and include carbon fixation in the definition. So let photosynthesis now be the use of sunlight to split water and to reduce carbon dioxide to carbohydrate. Many other relevant definitions exist but this type of photosynthesis, carried out by cyanobacteria, algae and plants, is ecologically, geologically and economically so important that the definition is justified.
Photosynthesis, defined in this way, needs
A reaction center complex = a system consisting of a pigment molecule (primary donor) and an electron acceptor (molecule) arranged so that the pigment, when excited by light, reduces the acceptor. Furthermore, this reaction must be arranged so that immediate reversal does not usually occur. In natural oxygenic photosynthesis, two reaction center complexes (II and I, in this order) function in series, and in both the primary donor is a chlorophyll a molecule and the acceptor task is carried out by a series of several different molecules.
A catalyst for water oxidation that can donate to the primary donor. In natural photosynthesis, only Photosystem II has such a catalyst, composed of four Mn ions, a Ca ion and five oxygen atoms. The structure of the catalyst is fairly well known but there is no consensus about the details of the function.
A catalyst for carboxylation, carbon reduction and regeneration of the compound that becomes carboxylated. In natural photosynthesis, the enzymes of the Calvin-Benson cycle do all this.
An electron transfer chain connecting the acceptor from #1 and the carbon reduction mechanism of #3. It might be argued that this is not a basic requirement but due to the complexity of the whole system, I say that a chain of electron acceptors adds the required flexibility.
In addition to these basic requirements, all natural systems have pigment complexes for light harvesting. However, designs of artificial systems do not always have light harvesting complexes, suggesting that this is not a fundamental requirement.
Chlorophyll a is an excellent choice for the primary donor but artificial systems tend to favor ruthenium bipyridine for this task. Other substances can work, especially if ultraviolet radiation (arriving from the Sun in small quantities) is used instead of visible light. Several materials have recently found to catalyze water oxidation, although none of them splits water with the same rate and with equally good efficiency as the natural complex. For the carbon fixation part, the natural system is superb and no real plans to design a replacement have been presented. Long electron transfer chains are difficult to design but short artificial chains can be made to function.
Natural systems have two reaction center complexes in series and would not function with one. This, however, is more like a design parameter than a basic requirement. If only one reaction center complex is used, then one has to discard a larger part of the spectrum of sunlight. Natural oxygenic photosynthesis discards about half of solar photons because they carry too little energy.
In addition to the machinery as described above, one of course needs appropriate electromagnetic radiation, water and carbon dioxide.
Let us define photosynthesis first. In this answer, I will narrow the general definition by considering only oxygen-producing (oxygenic) phototosynthesis and include carbon fixation in the definition. So let photosynthesis now be the use of sunlight to split water and to reduce carbon dioxide to carbohydrate. Many other relevant definitions exist but this type of photosynthesis, carried out by cyanobacteria, algae and plants, is ecologically, geologically and economically so important that the definition is justified.
Photosynthesis, defined in this way, needs
A reaction center complex = a system consisting of a pigment molecule (primary donor) and an electron acceptor (molecule) arranged so that the pigment, when excited by light, reduces the acceptor. Furthermore, this reaction must be arranged so that immediate reversal does not usually occur. In natural oxygenic photosynthesis, two reaction center complexes (II and I, in this order) function in series, and in both the primary donor is a chlorophyll a molecule and the acceptor task is carried out by a series of several different molecules.
A catalyst for water oxidation that can donate to the primary donor. In natural photosynthesis, only Photosystem II has such a catalyst, composed of four Mn ions, a Ca ion and five oxygen atoms. The structure of the catalyst is fairly well known but there is no consensus about the details of the function.
A catalyst for carboxylation, carbon reduction and regeneration of the compound that becomes carboxylated. In natural photosynthesis, the enzymes of the Calvin-Benson cycle do all this.
An electron transfer chain connecting the acceptor from #1 and the carbon reduction mechanism of #3. It might be argued that this is not a basic requirement but due to the complexity of the whole system, I say that a chain of electron acceptors adds the required flexibility.
In addition to these basic requirements, all natural systems have pigment complexes for light harvesting. However, designs of artificial systems do not always have light harvesting complexes, suggesting that this is not a fundamental requirement.
Chlorophyll a is an excellent choice for the primary donor but artificial systems tend to favor ruthenium bipyridine for this task. Other substances can work, especially if ultraviolet radiation (arriving from the Sun in small quantities) is used instead of visible light. Several materials have recently found to catalyze water oxidation, although none of them splits water with the same rate and with equally good efficiency as the natural complex. For the carbon fixation part, the natural system is superb and no real plans to design a replacement have been presented. Long electron transfer chains are difficult to design but short artificial chains can be made to function.
Natural systems have two reaction center complexes in series and would not function with one. This, however, is more like a design parameter than a basic requirement. If only one reaction center complex is used, then one has to discard a larger part of the spectrum of sunlight. Natural oxygenic photosynthesis discards about half of solar photons because they carry too little energy.
In addition to the machinery as described above, one of course needs appropriate electromagnetic radiation, water and carbon dioxide.
Similar questions