Need help, please. The reaction in gluconeogenesis catalyzed by Glyceraldehyde-3-phosphate dehydrogenase (GADPH) requires NADH. What are potential sources of cytosolic NADH?i. The conversion of Malate to Oxaloacetate (catalyzed by cytosolic malate dehydrogenase (MDH))ii. The conversion of 1,3 Biphosphoglycerate to Glyceraldehyde-3-phosphate (catalyzed by Glyceraldehyde 3 phosphate dehydrogenase (GAPDH))iii. The conversion of Lactate to Pyruvate (catalyzed by Lactate dehydrogenase (LDH))iv. The conversion of Oxaloacetate to Malate (catalyzed by mitochondrial malate dehydrogenase (MDH))Only i and iii are correctOnly i and ii are correctOnly i, ii, and iii are correctAll four (i-iv) are correctOnly ii is correctOnly i is correct

Gluconeogenesis is the metabolic pathway that generates glucose from non-carbohydrate precursors.…

Answered: The reaction in gluconeogenesis…

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 of the consequences of ethanol addiction is fattyliver disease, an illness in which liver cells accumulatetriacylglycerols, the esters derived from glycerol and fattyacids. Ethanol is oxidized in the cytoplasm of liver cells byalcohol dehydrogenase and aldehyde dehydrogenase to yieldacetate and 2 NADH. Acetate is then transported into themitochondrion, where it is converted to acetyl-CoA andmetabolized by the citric acid cycle. When alcohol is consumed in excessive quantities, the resulting high levels ofNADH cause metabolic abnormalities, one of which is highlevels of fatty acid synthesis. Fatty acid synthesis, also acytoplasmic process, uses acetyl-CoA as a substrate andNADPH as a reducing agent. Determine how a high level ofcytoplasmic NADH provides a source of NADPH for fattyacid synthesis.
Briefly describe the biological rationale for each of the following allosteric phenomena: (a) activation of pyruvate carboxylase by acetyl-CoA; (b) activation of pyruvate dehydrogenase kinase by NADH; (c) inhibition of isocitrate dehydrogenase by NADH; (d) activation of isocitrate dehydrogenase by ADP; (e) inhibition of α-ketoglutarate dehydrogenase by succinyl-CoA; (f) activation of pyruvate dehydrogenase phosphatase by Ca2 +.
Briefly describe the biological rationale for each of the following allosteric phenomena: (a) activation of pyruvate carboxylase by acetyl-CoA; (b) activation of pyruvate dehydrogenase kinase by NADH; (c) inhibition of isocitrate dehydrogenase by NADH; (d) activation of isocitrate dehydrogenase by ADP; (e) inhibition of a-ketoglutarate dehydrogenase by succinyl-CoA; (f) activation of pyruvate dehydrogenase phosphatase by Ca2+.
The oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate, catalyzed by glyceraldehyde 3- phosphate dehydrogenase, proceeds with an unfavorable equilibrium constant ( K'eq= 0.08; ΔG′° = 6.3 kJ/mol), yet the flow through this point in the glycolytic pathway proceeds smoothly. How does the cell overcome the unfavorable equilibrium?
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
What are the similarities and differences between the reactions catalyzed by pyruvate dehydrogenase and a-ketoglutarate dehydrogenase?
Because dichloroacetate inhibits the enzyme pyruvatedehydrogenase kinase, this compound has been used,with limited results, to treat lactic acidosis. The phosphorylation of the a-subunit of the pyruvate dehydrogenasecomponent of the pyruvate dehydrogenase complex bypyruvate dehydrogenase kinase causes complete loss ofenzymatic activity. Describe the theory behind the clinicaluse of dichloroacetate.
The glycerol derived from lipolysis of triacylglycerols is converted into glyceraldehyde 3-phosphate, which then enters into step 6 of the glycolysis pathway. What further transformations are necessary to convert glyceraldehyde 3-phosphate into pyruvate?
The enzyme, dihydrolipoamide dehydrogenase is present in both pyruvate dehydrogenase complex and α-ketoglutarate dehydrogenase complex. What type of reaction is catalyzed by these complexes? Describe the role of dihydrolipoamide dehydrogenase in these reactions.
Phosphoglycerate mutase (PGM) catalyzes the interconversion of 3-phosphoglycerate (3PG) and 2-phosphoglycerate (2PG) in the glycolytic and gluconeogenic pathways. a) To what enzyme class does PGM belong? b) There are two distinct classes of PGM, one which is dependent on 2,3-bisphosphoglycerate (2,3-BPG), dPGM, and one which is not, iPGM. dPGM uses acid base chemistry and a phosphorylated histidine residue to interconvert 3PG and 2PG. The dPGM reaction proceeds with formation of 2,3-BPG as an intermediate. Propose a mechanism for the dPGM-catalyzed conversion of 3PG to 2PG that is consistent with this information. c) What is the purpose of 2,3-BPG (i.e., why does dPGM require it)?
What is the metabolic significance of the following observations? (a) Only the liver form of pyruvate kinase is inhibited by alanine, and (b) only gluconeogenic tissues contain appreciable levels of glucose-6-phosphatase.
The pyruvate dehydrogenase complex catalyzes the oxidative decarboxylation of pyruvate to form acetyl‑CoA. E1E1 , E2E2 , and E3E3 are abbreviations for the enzymes of the complex. Classify the enzyme names, prosthetic groups, and reactions as E1E1 , E2E2 , or E3E3 .

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