TABLE 13.2 Reactions of the citric acid cycle AG" AG Reaction Enzyme (kJ/mol) (kJ/mol) 1. Acetyl-CoA + oxaloacetate + H2O citrate + CoA-SH + H+ Citrate synthase -32.2 --55 2а. Citrate cis-aconitate + H,O Aconitase +6.3 2b. cis-Aconitate + H20 isocitrate Aconitase 3. Isocitrate + NAD a-ketoglutarate + CO2 + NADH Isocitrate dehydrogenase -11.6 --20 a-Ketoglutarate dehydrogenase complex 4. a-Ketoglutarate + NAD+ + CoA-SH = succinyl-CoA + CO2 + NADH -33.5 -40 5. Succinyl-CoA + P + ADP (GDP) succinate + ATP (GTP) + CoA-SH Succinyl-CoA synthetase -3.8 -0 6. Succinate + FAD (enzyme-bound) fumarate + FADH2 (enzyme-bound) Succinate dehydrogenase 7. Fumarate + H20 2 L-malate Fumarase -3.8 8. L-Malate + NAD+ oxaloacetate + NADH + H+ Malate dehydrogenase +29.7 Net -48.0 115 Note: AG°' value for reaction 3 was calculated from the E' values for a-ketoglutarate/isocitrate (-0.38 V) and NAD/NADH (-0.32 V).

TABLE 13.2 Reactions of the citric acid cycle AG" AG Reaction Enzyme (kJ/mol) (kJ/mol) 1. Acetyl-CoA + oxaloacetate + H2O citrate + CoA-SH + H+ Citrate synthase -32.2 --55 2а. Citrate cis-aconitate + H,O Aconitase +6.3 2b. cis-Aconitate + H20 isocitrate Aconitase 3. Isocitrate + NAD a-ketoglutarate + CO2 + NADH Isocitrate dehydrogenase -11.6 --20 a-Ketoglutarate dehydrogenase complex 4. a-Ketoglutarate + NAD+ + CoA-SH = succinyl-CoA + CO2 + NADH -33.5 -40 5. Succinyl-CoA + P + ADP (GDP) succinate + ATP (GTP) + CoA-SH Succinyl-CoA synthetase -3.8 -0 6. Succinate + FAD (enzyme-bound) fumarate + FADH2 (enzyme-bound) Succinate dehydrogenase 7. Fumarate + H20 2 L-malate Fumarase -3.8 8. L-Malate + NAD+ oxaloacetate + NADH + H+ Malate dehydrogenase +29.7 Net -48.0 115 Note: AG°' value for reaction 3 was calculated from the E' values for a-ketoglutarate/isocitrate (-0.38 V) and NAD/NADH (-0.32 V).

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter27: Metabolic Integration And Organ Specialization

Section: Chapter Questions

Problem 8P: Ethanol as a Source of Metabolic Energy (Integrates with Chapters 19 and 20.) Acetate produced in...

See similar textbooks

Similar questions

Complete oxidation of a 16-carbon fatty acid can yield 129 molecules of ATP Study Figure 19.2 and determine how many ATP molecules would be generated if a 16-carbon fatly acid were metabolized solely by the TCA cycle, in the form of S acetyl-CoA molecules.
Extending the Mechanism of Methylmalonyl-CoA Mutase to Similar Reactions Based on the mechanism for the methylmalonyl-CoA mutase (see problem 14), write reasonable mechanisms for the following reactions shown.
Ethanol as a Source of Metabolic Energy (Integrates with Chapters 19 and 20.) Acetate produced in ethanol metabolism can be transformed into acetyl-COA by the acetyl thiokinase reaction: Acetate+ATP+CoASHacetyleCoA+AMP+PPiAcetyle-CoA then can enter the citric acid cycle and undergo oxidation to 2 CO2by this route, assuming oxidative phosphorylation is part of the process? (Assume all reactions prior to acetyl-CoA entering the citric acid cycle occur outside the mitochondrion). Per carbon atom, which is a better metabolic fuel, ethanol or glucose? That is, how many ATP equivalents per carbon atom are generated by combustion of glucose versus ethanol to CO2?
25. The AG" values for the two reactions are given. 1. 2. oxaloacetate + acetyl-CoA + H₂O → citrate + COASH oxaloacetate + acetate → citrate Enzymes for reactions 1 and 2 are citrate synthase and citrate lyase, respectively. Determine the AG" for the hydrolysis of acetyl-CoA acetyl-CoA + H₂O acetate + COASH + H+ plane een isoimorfbold bns (94) opg Vp1903 9911 AG¹⁰ ? AGO = -32.2 kJ/mol AG"=-1.9 kJ/mol
Consider the docosanoic acid, C21H43CO2H a. Label the a and B carbons b. Draw the acyl CoA derived from this fatty acid c. How many acetyl CoA molecules are formed by complete B-oxidation? d. How many cycles of B-oxidation are needed for complete oxidation? e. How many molecules of ATP are formed from the complete catabolism of this fatty acid?
Arrange the steps of breakdown of oleic acid (pictured below) in the correct order. 1 2 3 4 5 activation by acyl-CoAsynthe ✓ [Choose ] one cycle ofß-oxidationbeginning at the enoyl-CoAhydratasestep three cycles ofẞ-oxidation five cycles ofß-oxidation activation by acyl-CoAsynthetase enoyl-CoAisomeraseactivity enoyl-CoAisomeraseactivity V one cycle ofß-oxidationbegini V five cycles ofß-oxidation OH
Page > of 6 ZOOM + TCA cycle, oxidative phosphorylation, metabolic regulation TCA cycle (Ch. 16) 1. The citric acid cycle has eight enzymes: citrate synthase, aconitase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, succinyl-CoA synthetase, succinate dehydrogenase, fumarase, and malate dehydrogenase. (a) Write a balanced equation for the reaction catalyzed by each enzyme. (b) Name the cofactor(s) required by each enzyme reaction. (c) For each enzyme determine which of the following describes the type of reaction(s) catalyzed: condensation (carbon–carbon bond formation); dehydration (loss of water); hydration (addition of water); decarboxylation (loss of CO2); oxidation-reduction; substrate-level phosphorylation; isomerization. (d) Write a balanced net equation for the catabolism of acetyl-CoA to CO2.
Consider docosanoic acid C12H43CO2H a. Label the alpha and beta Carbons. Show the beta-oxidation in an EXPANDED structure. b. Draw each acyl CoA derived from this fatty acid. c. How many acetyl Co A molecules are formed by complete beta-oxidation? d. How many cycles of beta-oxidation are needed for complete oxidation? e. How many molecules of ATP are formed from the complete catabolism of this fatty acid? Show the complete computation. f. How many moles of ATP per gram of fatty acid is formed from the complete catabolism of the given fatty acid? g. What is the molar mass of the given fatty acid? Solution: Show here the complete computations, [from a to e]
Consider the complete oxidation of one mole of the fatty acyl CoA of myristic acid (14:0). Determine the following (Type the numerical value only - e.g. 1): 1. rounds of B-oxidation 2. total no. of acetyl CoA produced 3. total no. of NADH produced from all rounds of B-oxidation 4. total no. of FADH2 produced from all rounds of B-oxidation 5. total no. of NADH produced from the oxidation of all acetyl CoA in the TCA cycle 6. total no. of FADH, produced from the oxidation of all acetyl CoA in the TCA cycle 7. total ATP yield
9. The equation below depicts the first step of the citric acid cycle. H0 CoA-SH CH-C + 0=C-CO0 HO C-COO citrate s-COA ČH2-COO synthase ČH2 -CO0 Citrate Acetyl-CoA Oxaloacetate AG" = -32.2 kJ/mol a) Explain the chemical conversions that take place during this step. b) Why is this reaction energetically favorable? Explain.
1) Humans do not undergo net synthesis of carbohydrate from acetyl- CoA, yet carbons of acetyl -CoA can be incorporated into glucose and amino acids. Show pathways as to how this can happen. 2) A molecule -X inhibits oxidation of stearoyl-CoA by isolated mitochondria but has no effect on palmitoyl-carnitine oxidation, explain.
Page of 6 ZOOM + name: 3. In the last reaction of the citric acid cycle, malate is dehydrogenated to regenerate the oxaloacetate necessary for the entry of acetyl-CoA into the cycle: L-Malate + NAD+ → oxaloacetate + NADH + H* AG'° = 30.0 kJ/mol (a) Calculate the equilibrium constant for this reaction at 25 °C. (b) Because AG°' assumes a standard pH of 7, the equilibrium constant calculated in (a) corresponds to [oxaloacetate][NADH] Keq [L-malate][NAD*] The measured concentration of L-malate in rat liver mitochondria is about 0.20 mM when [NAD*]/[NADH] is 10. Calculate the concentration of oxaloacetate at pH 7 in these mitochondria. (c) To appreciate the magnitude of the mitochondrial oxaloacetate concentration, calculate the number of oxaloacetate molecules in a single rat liver mitochondrion. Assume the mitochondrion is a sphere of diameter 2.0 microns.