Carbon dioxide in photosynthesis

The most exciting applications of esr are in the study of radical intermediates in organic reactions. Considerable use has been made of the technique in biochemical reactions and it has been shown that radicals are generated and decay in oxidations brought about by enzymes. Radicals also have been detected by esr measurements in algae that fix carbon dioxide in photosynthesis. The character of the radicals formed has been found to depend upon the wavelength of the light supplied for photosynthesis. 

Like sodium chloride, carbon dioxide is relatively stable. Carbon dioxide is used in some types of fire extinguishers because it does not support burning. Figure 4.4. Photosynthesis is probably the most significant chemical reaction of carbon dioxide. In photosynthesis, plants use energy from the sun to combine carbon dioxide and water chemically to make simple sugars. Plants use these sugars as raw materials to make many... 

Such a theory of metabolic and photosynthetic evolution goes far towards explaining the similarities and differences amongst the various metabolic processes as we know them today. The path of carbon reduction in photosynthesis employs many reactions which are similar to those employed by heterotrophic organisms in the oxidation of carbohydrates. The apparatus for transporting electrons from water to the point of reduction of carbon dioxide in photosynthesis is similar in many aspects to the apparatus used for the transport of electrons from the oxidation of carbohydrate to oxygen in respiration. 

Photosynthetic earboxylation the enzymatic fixation of carbon dioxide in photosynthesis. In C-3 plants, the photosynthetic earboxylation enzyme is ri-bulose iirphosphate carboxylase (EC 4.1.1.39). In C-4 plants it is phosphoeno/pyruvate carboxylase (EC 41.1.31). P. c. is the first step of carbon dioxide assimilation in photosynthesis, and one of the dark reactions. 

Microscopic plant life— phytoplankton—is scarce in certain parts of the ocean (Figure 1.22 T). Several years ago scientists proposed that this scarcity is caused by the lack of plant nutrients, primarily iron. Because phytoplankton take up carbon dioxide in photosynthesis, it was also proposed that relatively small amounts of iron distributed in appropriate regions of the oceans could reduce atmospheric carbon dioxide, thereby reducing global warming. If the phytoplankton sank to the bottom of the ocean when they died, the carbon dioxide would not return to the atmosphere when the microbes decomposed. 

Many of the industrial gases are of fundamental importance for biological processes. Most life forms obtain their energy by metabolizing nutrients with oxygen, producing the end products water and carbon dioxide. In photosynthesis, carbon dioxide and water... 

Except as an index of respiration, carbon dioxide is seldom considered in fermentations but plays important roles. Its participation in carbonate equilibria affects pH removal of carbon dioxide by photosynthesis can force the pH above 10 in dense, well-illuminated algal cultures. Several biochemical reactions involve carbon dioxide, so their kinetics and equilibrium concentrations are dependent on gas concentrations, and metabolic rates of associated reactions may also change. Attempts to increase oxygen transfer rates by elevating pressure to get more driving force sometimes encounter poor process performance that might oe attributed to excessive dissolved carbon dioxide. 

Scientists have been able to compare the seasonal changes in atmospheric carbon dioxide to the seasonal changes in photosynthesis in the Northern Hemisphere. Plants take up more carbon dioxide in... 

Benniston AC, Haniman A (2008) Artificial photosynthesis. Materials Today 11 26-34 Inoue T, Fujishima A, Konishi S, Honda K (1979) Photoelectrocatalytic reduction of carbon dioxide in aqueous suspensions of semiconductor powders. Nature 277 637-638 Halmann M (1978) Photoelectrochemical reduction of aqueous carbon dioxide on p-type gallium phosphide in liquid junction solar cells. Nature 275 115-116 Heminger JC, Carr R, Somorjai GA (1987) The photoassisted reaction of gaseous water and carbon dioxide adsorbed on the SrH03 (111) crystal face to form methane. Chem Phys Lett 57 100-104... 

C3 plants Plants as, for example, cotton and wheat, in which, during the photosynthesis process, a stable compound consisting of three bonded carbon atoms is first formed during the fixation of carbon derived from carbon dioxide in the plants over 95% of the plant species on the earth are C3 plants see C4 and CAM plants. 

The photoassisted reduction of aqueous carbon dioxide in the presence of inorganic minerals has been examined as a model of prebiological photosynthesis,120 a potential precursor to the photosynthetic fixation of C02 by plants. 

When the earth was formed about 4.5 billion years ago, 95% of the atmosphere consisted of carbon dioxide. The emergence of plant life changed the atmosphere since plants, through the process of photosynthesis, absorb carbon dioxide. Carbon from the atmosphere was absorbed into the vegetation and when the vegetable matter died, it decomposed, and formed coal and oil. This dropped the carbon dioxide in the atmosphere to less than 1%. 

Photosynthesis and respiration help to maintain the concentrations of oxygen and carbon dioxide in the atmosphere. Respiration is the process by which carbohydrates (most commonly glucose) are broken down for the release of energy needed for life processes. Photosynthesis uses carbon dioxide and produces oxygen. Respiration does the opposite—it uses oxygen and produces carbon dioxide. Plants and algae carry on photosynthesis, while animals carry... 

As discussed in the answer to exercise 94, trees and other photosynthetic plants absorb atmospheric carbon dioxide in the summer, which causes a decrease in atmospheric CO, levels by the fall. During the winter, the plants lose their leaves and photosynthesis stops. The fall and winter decay of the organic matter generates carbon dioxide, which increases the atmospheric CO, levels by the spring. Most of the land mass of our planer is located in the northern hemisphere. Therefore, that s where most of the CO,-consuming photosynthesis from trees and plants takes place. 

Although carbon dioxide in the atmosphere is not present at toxic levels and is required by plants for photosynthesis, why may it turn out to be the ultimate air pollutant ... 

The use of membrane introduction mass spectrometry (MIMS) was first reported in 1963 by Hoch and Kok for measuring oxygen and carbon dioxide in the kinetic studies of photosynthesis [46], The membrane module used in this work was a flat membrane fitted on the tip of a probe and was operated in the MIS mode. The permeated anaytes were drawn by the vacuum in the MS through a long transfer line. Similar devices were later used for the analysis of organic compounds in blood [47], Memory effects and poor reproducibility plagued these earlier systems. In 1974, the use of hollow-fiber membranes in MIMS was reported, which was also operated in the MIS mode [48], Lower detection limits were achieved thanks to the larger surface area provided by hollow fibers. However, memory effects caused by analyte condensation on the wall of the vacuum transfer line remained a problem. 

---