Calvin-Benson cycle carbon dioxide

All the O atoms evolved as Og come from water none comes from carbon dioxide. But 12 O atoms are evolved as 6 Og, and only 6 O atoms appear as 6 HgO in the equation. Also, 6 COg have 12 O atoms, yet there are only 6 O atoms in CgHigOg. How can yon account for these discrepancies Hint Consider the partial reactions of photosynthesis ATP synthesis, NADP reduction, photolysis of water, and the overall reaction for hexose synthesis in the Calvin-Benson cycle.)... 

Purple sulfur bacteria fix carbon dioxide using the Calvin-Benson cycle, but green sulfur bacteria use a completely different pathway, the reverse tricarboxylic acid cycle. Other photosynthetic bacteria use still different pathways for CO2 fixation (Perry and Staley, 1997). 

The light independent reactions take place in the stroma with the help of ATP and NADPH. In a process called the Calvin-Benson cycle, or carbon fixation, carbon dioxide from the atmosphere is captured and converted into carbohydrates [135]. The reaction is catalyzed by the enzyme RuBisCO (ribulose-1,5-biphosphate... 

The overall reaction of carbon dioxide reduction in the Calvin-Benson cycle (Fig. 17-14) becomes... 

Calvin cycle (aka Calvin-Benson Cycle or Carbon Fixation) Series of biochemical, enzyme-mediated reactions during which atmospheric carbon dioxide is reduced and incorporated into organic molecules, eventually some of this forms sugars. In eukaryotes, this occurs in the stroma of the chloroplast. 

PGA (phosphoglycerate) A three-carbon molecule formed when carbon dioxide is added to ribulose biphosphate (RuBP) during the dark reaction of photosynthesis (Calvin, or Calvin-Benson Cycle). PGA is converted to PGAL, using ATP and NADPH. 

The lithoautotrophs have to form cellular materials from carbon dioxide. The process to change carbon dioxide into organic compounds is called fixation of carbon dioxide. On the basis of the knowledge to date, all algae and cyanobacteria, and many of the plants, fix carbon dioxide through the Calvin-Benson cycle (or reductive pentose phosphate cycle) (Bassham et al., 1954), while the plants of 20 families and 1200 species have been known to fix carbon dioxide through the Hatch-Slack pathway (or C4 dicarboxylate pathway) (Hatch et al., 1967). 

Plants are divided into two groups for the fixing mechanisms of carbon dioxide plants of one group use the Calvin-Benson cycle, while those of the other group... 

As a result, oxaloacetate (OAA, C4-compound) is formed unlike the case of the Calvin-Benson cycle in which 3-phosphoglycerate (C3-compound) is formed. The pathway in the fixation of carbon dioxide by the catalysis of PEP-carboxylase is observed in sugar cane, corn, etc., and is called the Hatch-Slack pathway (Hatch et al., 1967). The plants having the Hatch-Slack pathway have chloroplasts both in mesophyll cells and in vascular bundle sheath cells, and the Hatch-Slack pathway occurs in the mesophyll cells. Oxaloacetate formed by the fixation of carbon dioxide in the mesophyll cells is reduced to malate. Malate thus formed moves to the vascular bundle sheath cells and releases carbon dioxide there. Carbon dioxide released is fixed by the catalysis of Rubisco, and the organic compounds are formed through the Calvin-Benson cycle. (Fig. 6.3). 

The plants producing organic compounds from carbon dioxide through the Calvin-Benson cycle are called C3-plants, while the plants producing organic compounds from carbon dioxide through the Hatch-Slack pathway are called C4-plants. 

Carbon Dioxide-Fixing Pathways Other than the Calvin-Benson Cycle in the Lithoautotrophs... 

As already mentioned, cyanobacteria and most of the chemolithoautotrophic bacteria fix carbon dioxide through the Calvin-Benson cycle, but some litho-autotrophic bacteria fix carbon dioxide through other pathways. When the green phototrophic bacterium Chloroflexus aurantiacus grows lithoautotrophically, the bacterium fixes carbon dioxide through the 3-hydroxypropionate cycle (Ivanovsky... 

Plants utilize carbon dioxide in two ways. Most allow the carbon dioxide they absorb to enter the Calvin-Benson cycle immediately and in this case the first stable organic compound produced is glyceraldehyde-3-phosphate. This contains three carbon atoms so plants operating in this away are known as C3 plants. A few plants, including maize, sugar cane and other tropical and sub-tropical grasses, operate differently in order to conserve water. Prior to the Calvin-Benson cycle, these plants have a special enzyme, known as phosphoenolpyruvate (PEP) to trap carbon dioxide and turn it into... 

The NADPH and ATP generated are used within the chloroplast to fix carbon dioxide (CO2) and reduce it to sugar. This sequence of reactions is called the Calvin-Benson-Bassham cycle and this cycle results in the production of the phosphorylated 3-carbon sugar glyceraldehyde-3-phosphate, also called triose. This triose sugar is exported out of the chloroplast and in this course we will refer to it as CH2O which is the chemical composition of sugar when normalized to 1 carbon atom. 

Carbon dioxide (CO2) is processed through the Calvin cycle ([or the Calvin-Benson-Bassham cycle] which is also referred to as the RPP cycle) vide infra. 

Although some plants, such as those called C4 and those known as using Crassulacean acid metabolism (CAM) photosynthesis (i.e., xerophytes) initially capture the carbon dioxide (CO2) differently than the C3 plants do, they too subsequently release it to the Calvin cycle (M. Calvin [1911-1997], professor. University of California, Berkeley, since 1937, Nobel Prize in Chemistry 1961 Bassham, I Benson, A. Calvin, M. [1950]./ Biol. C/iem., 1950,7S5,781). 

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