Glycolysis pathway steps

Acetyl CoA formed in this reaction can enter the citric acid cycle on its way to complete oxidation to CO2. The NAD needed for the conversion of pyruvate to acetyl CoA (Reaction 13.7) and for the operation of the glycolysis pathway (Step 6) is regenerated when NADH transfers its electrons to O2 in the electron transport chain. 

In contrast with the well-known Embden-Meyerhof-Pamass glycolysis pathway for the conversion of hexose sugars to alcohol, the steps in conversion of ethanol to acetic acid remain in some doubt. Likely, ethanol is first oxidized to acetaldehyde and water (39). For further oxidation, two alternative routes are proposed more likely, hydration of the acetaldehyde gives CH2CH(OH)2, which is oxidized to acetic acid. An alternative is the Cannizzaro-type disproportionation of two molecules of acetaldehyde to one molecule of ethanol and one molecule of acetic acid. Jicetobacter... 

Further steps in glycolysis use the D-glyceraldehyde 3-phosphate fonned in the aldolase-catalyzed cleavage reaction as a substrate. Its coproduct, dihydroxyacetone phosphate, is not wasted, however. The enzyme triose phosphate isomerase converts dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate, which enters the glycolysis pathway for further transfonnations. 

Active Figure 29.7 MECHANISM The 10-step glycolysis pathway for catabolizing glucose to two molecules of pyruvate. Individual steps are described in the text. Sign in at www.thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

Figure 17-7 Outline of the glycolysis pathway by which hexoses are broken down to pyruvate. The ten enzymes needed to convert D-glucose to pyruvate are numbered. The pathway from glycogen using glycogen phosphorylase is also included, as is the reduction of pyruvate to lactate (step 11). Steps 6a-7, which are involved in ATP synthesis via thioester and acyl phosphate intermediates, are emphasized. See also Figures 10-2 and 10-3, which contain some additional information.

One gram of edianol should yield 1.304 g acetic acid. Practical yields arc 77-85%. In contrast with the well-known Embdcn-Mcycrhof-Parnass glycolysis pathway for the conversion of tiexose sugars to alcohol, lire steps in conversion of ethanol to acetic acid remain in some doubt. 

The ten-step glycolysis pathway for catabolizing glucose to pyruvate. The individual steps are described in more detail in the text. 

Glyceraldehyde 3-phosphate continues on in the glycolysis pathway, but dihydroxyacetone phosphate is first isomerized by the enzyme triose phosphate isomerase. As in the glucose-to-fructose conversion of step 2, the... 

Inhibitors may serve any of the several (ten) sequential steps involved in the glycolysis pathway. A partial listing includes certain metallic or mineral substances, notably calcium and magnesium (as the ions Ca and Mg ). These are among the essential minerals found in the diet. Lithium is another inhibitor, which is notably... 

In the overview of glycolysis we noted that the pyruvate produced must be used up in some way so that the pathway will continue to produce ATP. Similarly, the NADH produced by glycolysis in step 6 (see Figure 21.8) must be reoxidized at a later time, or glycolysis will grind to a halt as the available NAD+ is used up. If the cell is functioning under aerobic conditions, NADH will be reoxidized, and pyruvate will be completely oxidized by aerobic respiration. Under anaerobic conditions, however, different types of fermentation reactions accomplish these purposes. Fermentations are catabolic reactions that occur with no net oxidation. Pyruvate or an organic compound produced from pyruvate is reduced as NADH is oxidized. We will examine two types of fermentation pathways in detail lactate fermentation and alcohol fermentation. 

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