Consider ³H-labeled pyruvate (containing three ³H at C3) and ¹4C-labeled OAA (¹4C at C3) are added to apreparation of mitochondria in which pyruvate dehydrogenase and the citric acid cycle enzymes are functional.Assume the labeled compounds react to form citrate that is labeled with both ³H and ¹4C. Assume also that oncelabel is lost from a citric acid cycle intermediate that it does not become reincorporated.lfoxaloacetate (OAA)3H3H3Hpyruvate(a) Show the distribution of ³H and ¹4C in the citrate that is initially formed from the ¹4C-labeled OAA and the3H-labeled ACS-CoA.

Here we are tracking the hydrogen atoms in the methyl group of pyruvate and a carbon between two…

Answered: Consider ³H-labeled pyruvate…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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One hundred oxaloacetate molecules located in one hundred different cells are labeled at every carbon with 14C. These radiolabeled oxaloacetate molecules will individually pass through one round of the citric acid cycle to be regenerated (i.e. one oxaloacetate in each cell will go through only one round of the TCA cycle). Draw a diagram that represents each carbon atom in oxaloacetate before and after one round of the TCAcycle. Make sure to distinguish 14C and non-radiolabeled carbon in oxaloacetate. 1) Indicate the two possible configurations of the regenerated oxaloacetate molecules after one round of the TCA cycle by shading the appropriate carbons (if any) that would be radiolabeled, and 2) give the percentage for each configuration. (
Consider the fate of pyruvate labeled with 14C in each of the following posi- tions: carbon 1 (carboxyl), carbon 2 (carbonyl), and carbon 3 (methyl). Pre- dict the fate of each labeled carbon during one turn of the citric acid cycle.
Perform a pyruvate dehydrogenase reaction and a single turn of the citric acid cycle using an oxaloacetate molecule uniformly labeled with 18O and one pyruvate molecule uniformly labeled with 14C. Highlight the fate of all radioactively labeled atoms when complete.
a-Ketoglutarate plays a central role in the biosynthesis of several amino acids. Arrange the reactions to outline the net synthesis of a-ketoglutarate from pyruvate. Your proposed sequence must not include reactions that result in the net consumption of other citric acid cycle intermediates. Pyruvate + ATP + CO, + H,0 → oxaloacetate + ADP + P; + H+ a-Ketoglutarate + CoA + NAD+ → succinyl-CoA + CO,+NADH + H+ Pyruvate + CoA + NAD+ acetyl-CoA + CO,+NADH + H+ Oxaloacetate + acetyl-CoA → citrate + CoA Oxaloacetate + NADH + H+ malate + NAD+ Citrate → isocitrate Isocitrate + NAD+ a-ketoglutarate + CO,+NADH + H* 2.
You are carrying out an experiment in the lab to study the citric acid cycle. To do this, you add 14C-labeled pyruvate at carbon 3 (this is the methyl carbon) to metabolically active mitochondria. Based on your knowledge of the citric acid cycle, what is the location of the 14C-label in oxaloacetate after one turn of the cycle? How many turns of the cycle are required to release all of the the14C-label as CO2? Be sure to justify your answers using a thorough description, as your answer does not need to include any drawings of the intermediates (but, feel free to include one if you wish).
A mutated IDH1 isoenzyme is found in a high percentage of a type of brain cancer called glioblastoma. Instead of converting isocitrate to α-ketoglutarate, mutated IDH1 converts its substrate to 2-hydroxyglutarate, a circumstance that disrupts the citric acid cycle, among other effects. Review the structures of isocitrate and α-ketoglutarate and determine the structure of 2- hydroxyglutarate
The malaria parasite Plasmodium falciparum does not carry out oxidative phosphorylation and therefore does not use the citric acid cycle to generate reduced cofactors. Instead, the parasite converts amino acid–derived α ketoglutarate to succinate. Write an equation for the α-ketoglutarate → succinate conversion that follows (a) the oxidative (clockwise) path of the citric acid cycle or (b) the reductive (counterclockwise) path of the cycle.
In the citric acid cycle, malate dehydrogenase catalyzes the following reaction: Malate + NAD+ à oxaloacetate + NADH Calculate the standard free energy change for this reaction (∆Go’). Will it proceed as written under standard conditions? What do you think affects the actual free energy change (∆G) allowing for formation of oxaloacetate from malate?
One hundred oxaloacetate molecules located in one hundred different cells are labeled at every carbon with 14C. These radiolabeled oxaloacetate molecules will individually pass through one round of the citricacid cycle to be regenerated (i.e. one oxaloacetate in each cell will go through only one round of the TCA cycle).Draw a diagram that represents each carbon atom in oxaloacetate before and after one round of the TCA cycle.Make sure to distinguish 14C and non-radiolabeled carbon in oxaloacetate. 1) Indicate the two possible configurations of the regenerated oxaloacetate molecules after one round of the TCA cycle by shading theappropriate carbons (if any) that would be radiolabeled, and 2) give the percentage for each configuration.
ATP is an ALLOSTERIC INHIBITOR of the phosphofructokinase enzyme, which is a key catalyst for one of the first steps of Glycolysis. Citrate (citric acid) is a 6-carbon product of the first reaction of the Krebs Cycle (aka Citric Acid Cycle). Interestingly, Citrate enhances the inhibitory effect of ATP on phosphofructokinase. What is a likely explanation for the inhibitory effects of these molecules? Excess ATP and Citrate signal the cell that Glycolysis should be speeded up. Excess ATP and Citrate signal a positive feedback loop. Excess ATP and Citrate signal the cell that Glycolysis should be slowed. Excess ATP and Citrate compete for the active site of phosphofructokinase.
Deoxynucleotides (deoxynucleoside triphosphates) are the substrates for DNA synthesis. Calculate the number of glucose molecules that must be degraded to generate the energy required for the synthesis of 1000 deoxynucleotides used in DNA synthesis. Assume that glucose is oxidized completely to CO2 and H2O, the malate–aspartate shuttle is in operation, and NADPH is the equivalent of 4 ATP
In the mitochondrial disease MNGIE a deficiency of thymidine phosphorylase causes dTTP to accumulate in mitochondria. Describe the mechanism by which this occurs. A secondary effect is depletion of mitochondrial dCTP pools. Describe a plausible mechanism for this effect.

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