Substrate-level phosphorylation in glycolysis

In contrast to substrate level phosphorylation in glycolysis, mitochondrial oxidative phosphorylation is an efficient process in that it generates in excess of 30 ATP per mole of glucose. In essence, the movement of electrons along the respiratory chain or electron transport chain is coupled with phosphorylation of ADP. 

When grown under aerobic conditions, the yeast produces two ATP molecules from one molecule of glucose by substrate-level phosphorylation in glycolysis. The two molecules of pyruvate produced can then be completely oxidized to CO2, and each yields a further 15 molecules of ATP. This leads to a slow decrease in the concentration of glucose, a steady production of CO2, and relatively little change in the amount of ATP. Also, the two molecules of NADH can be reoxidized to NAD+ by the electron-transport system. (This produces yet more ATP, as discussed in Chap. 14.)... 

Which of the following could theoretically yield the maximum net number of molecules of ATP by substrate-level phosphorylation in glycolysis a molecule of sucrose, two molecules of glucose, or two molecules of fructose ... 

Cellular adenine nucleotides are compartmentalized by their very low diffusibility (due to their size and charge) with pools in the mitochondria, at the myofibrils, SR, and other sites of energy utilization. CK is located at those sites. Phosphocreatine is much smaller and less charged, and therefore much more mobile in cells than ATP. ATP produced by substrate-level phosphorylation in glycolysis may be used to rephosphorylate creatine in the sarcoplasm ... 

The hypothesis that a proton-motive force across the inner mitochondrial membrane is the immediate source of energy for ATP synthesis was proposed in 1961 by Peter Mitchell. Virtually all researchers working in oxidative phosphorylation and photosynthesis Initially opposed this chemlosmotic mechanism. They favored a mechanism similar to the well-elucidated substrate-level phosphorylation in glycolysis, in which oxidation of a substrate molecule is directly coupled to ATP synthesis. By analogy, electron transport through the... 

This reaction is one of two substrate level phosphorylations in glycolysis (the other is catalyzed by phosphoglycerate kinase). The enzyme is a key control point for glycolysis. 

If 1 molecule of glucose produces 2 molecules of ATP by substrate-level phosphorylation in glycolysis and the resulting 2 molecules of pyruvate can each yield 12.5 molecules of ATP when oxygen is available, how many glucose molecules will be necessary to produce 135 molecules of ATP by yeast grown under (a) aerobic and... 

Only about 5% of the ATP generated comes from substrate-level phosphorylation in glycolysis, and the remainder is obtained by the oxidative phosphorylation process. If the oxygen supply becomes temporarily inadequate, NADH is re-oxidised using pyruvic acid as the hydrogen acceptor. This enables glucose breakdown to work anaerobically. 

Figure 10.2 Substrate-level phosphorylation in glycolysis produces ATP.

Figure 23-2. Metabolism in the fed state. An adequate supply of carbohydrate provides glucose to replenish glycogen stores. Dietary protein provides amino acids for protein synthesis. Dietary carbohydrates, fats, and proteins can all be metabolized to generate ATP. (For clarity, ATP generation during P-oxidation of fatty acids and substrate-level phosphorylation during glycolysis is not depicted.) Excess dietary carbohydrates and amino acids are converted to fatty acids and, along with excess dietary fatty acids, stored as triacylglycerols. DHAP, dihydroxyacetone phosphate.

The total number of ATP produced by glycolysis and metabolism is 38 molecules, which includes a net of two from glycolysis (substrate level phosphorylation), 30 from the oxidation of 10 NADH molecules, four from oxidation of two FADH2 molecules, and two from substrate level phosphorylation in the Krebs cycle. 

The answer is f. (Murray, pp 182-189. Scriver, pp 2367-2424. Sack, pp 159—175. Wilson, pp 287-317.) In contrast to the case with glycolysis, the only site of substrate-level phosphorylation in the tricarboxylic acid cycle... 

Here we see the final substrate-level phosphorylation in the pathway, which is catalyzed by pyruvate kinase. Phosphoenolpyruvate serves as a donor of the phospho-ryl group that is transferred to ADP to produce ATP This is another coupled reaction in which hydrolysis of the phosphoester bond in phosphoenolpyruvate provides energy for the formation of the phosphoanhydride bond of ATP. The final product of glycolysis is p)mivate. 

Steps 1,3, and 10 of glycolysis are irreversible. Step 1 is the transfer of a phosphory 1 group from ATP to carbon-6 of glucose and is catalyzed by hexokinase. Step 3 is the transfer of a phosphoryl group from ATP to carbon-1 of fructose-6-phosphate and is catalyzed by phosphofructokinase. Step 10 is the substrate level phosphorylation in which a phosphoryl... 

The reaction involves a substrate-level phosphorylation in which phosphate from 1,3BPG is transferred to ADP to form ATP. The enzyme functions in the glycolysis, gluconeogenesis, and Calvin cycle pathways. 

Whereas ATP made in glycolysis and the TCA cycle is the result of substrate-level phosphorylation, NADH-dependent ATP synthesis is the result of oxidative phosphorylation. Electrons stored in the form of the reduced coenzymes, NADH or [FADHa], are passed through an elaborate and highly orga-... 

Examples of substrate level phosphorylation are to be found in glycolysis. Phos-phoglycerate kinase (PGK) and pyruvate kinase (PK) catalyse the following reactions ... 

The loss of AMP especially in active muscles is partly ameliorated by recycling of IMP via adenylosuccinate. Furthermore, because AMP is an important allosteric activator of PFK, regeneration of AMP ensures that glycolysis is fully active and able to provide pyruvate for the TCA cycle and some ATP via substrate level phosphorylation. 

Pyruvate kinase the last enzyme in aerobic glycolysis, it catalyzes a substrate-level phosphorylation of ADP using the high-energy substrate phosphoenolpyruvate (PEP). Pyruvate kinase is activated by fructose 1,6-bisphosphate from the PFK-1 reaction (feedforward activation). 

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