Concept explainers
Interpretation: To write an equation for the conversion of lactate to pyruvate in the Cori cycle that includes the structures of lactate and pyruvate.
Concept introduction: Glucose is converted to pyruvate by glycolysis
The Cori cycle is named after its discoverers, Gerty Radnitz Cori, and Carl Cori.
An overview of the Cori cycle is as follows:
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- Lactic acidosis, weakness, fatigue, and sleepiness are observed in patients with genetic defects of one if the enzymes of pyruvate dehydrogenase complex. Explain The causes of the elevation of lactate in the blood of such patients and the emergence of hypoenergetic state. For this purpose write the following: a) scheme of the metabolic pathway of glucose metabolism, that includes this reaction and calculates the energetic effect of the process, outlining the reactions coupled with the use and formation of ATP. b) reaction of the reduction of pyruvate and explain the reason for its acceleration inpatients that have such genetic defects.arrow_forwardThe glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconcogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP] and [Pi] =1 mM. Consider the following glycolytic reaction catalyzed by hexokinase: ATP + glucose = AG' = -16.7 kJ/mol ADP + glucose-6-phosphate (a) Calculate the equilibrium constant (K) for this reaction at 298 K, and from that, calculate the maximum [glucose-6-phosphate]/[glucose] ratio that would exist under conditions where the reaction is still thermody- namically favorable. (b) The reverse of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H,0 = glucose + P, AGr = -13.8 kJ/mol K= 262 for this reaction. Calculate the maximum ratio of [glucose]/ [glucose-6-phosphate] that would exist under conditions where the reaction is still thermodynamically favorable. (c) Under what cellular conditions would both directions in the…arrow_forwardThe conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in what type of net formation?arrow_forward
- Write a balanced equation for the synthesis of PRPP from glucose through the oxidative branch of the pentose phosphate pathway.arrow_forwardDefine GLUCONEOGENESIS. Give three reasons why is gluconeogenesis important in the Cori cycle?arrow_forwardThe reactions of the pyruvate dehydrogenase complex are required to generate the substrate that is fed into the TCA (Kreb’s) cycle from pyruvate. The 3 enzymes that make up this complex are pyruvate dehydrogenase (E1), dihydrolipoyl transacetylase (E2) dihydrolipoyl dehydrogenase (E3). a. Name the one diffusible reaction product (i.e. the product that is free to leave the enzyme complex) of each enzyme of the complex. b. Draw the “business end” of the fully reduced form of lipoic acid. c. Using words, fully describe the function of E3 in this complex. Your answer should include all cofactors used, all intermediates and products of this enzyme. DO NOT show any mechanisms for this part.arrow_forward
- Using the principles described in the text regarding pyridoxal phosphate mechanisms, propose a mechanism for the reaction catalyzed by serine hydroxymethyltransferase.arrow_forwardIn what condition and why is pyruvate converted to lactate?arrow_forwardThe half-reactions involved in the lactate dehydrogenase (LDH) reaction and their standard reduction potentials are (see attached)). Calculate ΔG at pH 7.0 for the LDH-catalyzed reduction of pyruvate under the following conditions: (a) [lactate]/[pyruvate] = 1 and [NAD+]/[NADH] = 1. (b) [lactate]/[pyruvate] = 160 and [NAD+]/[NADH] = 160. (c) [lactate]/[pyruvate] = 1000 and [NAD+]/[NADH] = 1000. (d) Discuss the eff ect of the concentration ratios in Parts a–c on the direction of the reaction.arrow_forward
- Which one of the five steps of the pyruvate dehydrogenase complex reaction is most likely to be metabolically irreversible? Explain.arrow_forwardThe 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.arrow_forwardThe glucose/glucose-6-phosphate substrate cycle involves distinct reactions of glycolysis and gluconeogenesis that interconvert these two metabolites. Assume that under physiological conditions, [ATP] = [ADP]; [P;] = 1 mM. Consider the glycolytic reaction catalyzed by hexokinase: ATP + glucose ADP + glucose-6-phosphate AG = - 16.7 kJ/mol (a) Calculate the equilibrium constant (K) for this reaction at 298°K, and from that, calculate the maximum [glucose-6-phosphate]/ Iglucose] ratio that would exist under conditions where the reaction is still thermodynamically favorable. (b) Reversal of this interconversion in gluconeogenesis is catalyzed by glucose-6-phosphatase: glucose-6-phosphate + H20 = glucose + P AG" = -13.8 kJ/molarrow_forward
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