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Oxidatio3 - = Fructose-6-phosphate is phosphorylated to...

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Oxidation-reduction, mechanisms of ATP generation, glycolysis, Krebs cycle Both respiratory and fermentative catabolism of glucose start with glycolysis - oxidation of glucose to pyruvic acid - "Glycolysis" translates roughly to "splitting of glucose", in reference to the splitting of the 6- carbon glucose molecule into two molecules of 3-carbon pyruvic acid - The most common glycolytic pathway, found in eucaryotes as well as bacteria, is the Embden- Meyerhof pathway (Tortora et al., Figure 5.11); the steps can be outlined as follows: = Glucose is phosphorylated, producing glucose-6-phosphate · In eukaryotes (such as ourselves!), the phosphate is obtained from hydrolysis of ATP · In bacteria, glucose is phosphorylated upon passage through the membrane and the phosphate is obtained from hydrolysis of phosphoenolpyruvic acid (PEP) to pyruvic acid = Glucose-6-phosphate is rearranged (isomerized) to form fructose-6-phosphate
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Unformatted text preview: = Fructose-6-phosphate is phosphorylated to fructose-1,6-diphosphate; the phosphate group is obtained from hydrolysis of ATP NOTICE THAT, AT THIS POINT, NO OXIDATION HAS OCCURRED AND NO ENERGY HAS BEEN OBTAINED; IN FACT, WE'VE USED UP TWO ATP MOLECULES IN THE PROCESS. = An enzyme catalyzes cleaveage of the 6-carbon fructose-1,6-diphosphate into two 3-carbon molecules - glyceraldehyde-3-phosphate and dihydroxyacetone phosphate · For organic chemistry fans (don't laugh; if there weren't any, we wouldn't have Teflon), this is the reverse of an aldol condensation · Another enzyme catalyzes the interconversion of dihydroxyacetone phosphate and glyceraldehyde-3-phosphate FOR THE PURPOSES OF DISCUSSING GLYCOLYSIS, WE CAN ASSUME THAT, AT THIS POINT, WE HAVE TWO MOLECULES OF GLYCERALDEHYDE-3-PHOSPHATE. THIS NEXT STEP IS CRITICAL FOR OBTAINING A NET ENERGY YIELD FROM GLYCOLYSIS...
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