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The Chemistry of WineFrom Blossom to Beverage and Beyond$
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David R. Dalton

Print publication date: 2018

Print ISBN-13: 9780190687199

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780190687199.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 26 October 2021

Working in the Dark

Working in the Dark

Chapter:
11 (p.58) Working in the Dark
Source:
The Chemistry of Wine
Author(s):

David R. Dalton

Publisher:
Oxford University Press
DOI:10.1093/oso/9780190687199.003.0019

Three turns of the Calvin cycle (Figure 11.1), allow the conversion of three (3) equivalents of carbon dioxide (CO2) (i.e., 3 C1 units) along with three (3) equivalents of the five-carbon carbohydrate derivative, ribulose-1,5-bisphosphate (i.e., 3 C5 units) to yield three (3) not yet isolated six-carbon adducts, 2-carboxy-3-ketoribitol-1,5-bisphosphate (3 C1 + 3 C5 = 3 C6) to form. The three (3) C6 species then undergo fragmentation to yield six (6) equivalents of the three (3) carbon dihydroxy monocarboxylate, 3-phosphoglycerate (i.e., 3 C6 = 6 C3). A cartoon representation of this process is shown in Scheme 11.1 for one of the three CO2 units. Of the six (6) three-carbon unit equivalents, five (5) are used to regenerate three (3) equivalents of ribulose-1,5-bisphosphate (i.e., 5 C3 = 3 C5), while the sixth three-carbon fragment is now available to combine with another to make a six (6) carbon sugar (2 C3 = 1 C6) such as glucose (C6H12O6) (Figure 11.2). Additionally, as shown in Figure 11.3, 3-phosphoglycerate can be used to make other small compound building blocks such as glyceric acid, lactic acid, pyruvic acid and even acetic acid (after decarboxylation). Ribulose-1,5-bisphosphate (often abbreviated as RuBP), using the enzyme ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39, carboxydismutase, rubisco), catalyzes the Mg2+- dependent conversion of the 1,5-bisphosphate ester of the carbohydrate ribulose with carbon dioxide (CO2) to produce two (2) equivalents of 3-phosphoglycerate (PGA). As shown in the Scheme 11.1 and 11.2. A hypothetical the six carbon intermediate, 2-carboxy-3-ketoribitol-1,5-bisphosphate, is often written. It is important to keep in mind that we want the 3-phosphoglycerate for purposes of construction of other important compounds. But, as noted above, three turns of the cycle are necessary to produce six (6) equivalents of 3-phosphoglycerate, and five (5) of them are reused in making the three (3) ribulose-1,5-bisphosphates necessary to turn the cycle three (3) times.

Keywords:   acetic acid, carbon dioxide, fructose, glyceric acid, imines, lactic acid, oxygen, phosphorylation, reduction, sedoheptulose

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