The glucose/glucose-6-phosphate substrate cycle involves distinctreactions of glycolysis and gluconeogenesis that interconvert thesetwo metabolites. Assume that under physiological conditions,[ATP] = [ADP]; [P;] = 1 mM.Consider the glycolytic reaction catalyzed by hexokinase:ATP + glucose ADP + glucose-6-phosphateAG = - 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 isstill thermodynamically favorable.(b) Reversal of this interconversion in gluconeogenesis is catalyzedby glucose-6-phosphatase:glucose-6-phosphate + H20 = glucose + PAG" = -13.8 kJ/mol K for this reaction is 262. Calculate the maximum ratio ofIglucose]/[glucose-6-phosphate] that would exist under conditionswhere the reaction is still thermodynamically favorable.(c) Under what cellular conditions would both directions in the sub-strate cycle be strongly favored?(d) What ultimately controls the direction of net conversion of asubstrate cycle such as this in the cell?

Glycolysis and gluconeogenesis are metabolic processes which are responsible for glucose degradation…

Answered: The glucose/glucose-6-phosphate…

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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The 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…
Pyruvate carboxylase catalyzes the first step of gluconeogenesis. ATP + HCO3─ + pyruvate → oxaloacetate + ADP + Pi ∆G0’ = ─2.1 kJ mol-1 a) Calculate ΔG for this reaction under the following physiological conditions: 370C, pH 7 [pyruvate] = [HCO3─] = 4.0 mM [oxaloacetate]= 2.0 mM [ATP] = 3.5 mM [Pi] = 5.0 mM [ADP] = 1.8 mM
Hexokinase catalyzes the first step of glycolysis, in which glucose is phosphorylated to form glucose‑6‑phosphate. Give two reasons why a Mg2+ cation is required to facilitate this reaction.
Although both hexokinase and phosphofructokinase catalyze irreversible steps in glycolysis and the hexokinase-catalyzed step is first, phosphofructokinase is nonetheless the pacemaker of glycolysis. What does this information tell you about the fate of the glucose 6- phosphate formed by hexokinase?
The final step in the pathway for the synthesis of glucose from lactate (gluconeogenesis) is: Glucose-6-phosphate + H20 5 Glucose + Pi When glucose-6-phosphate is incubated with the proper enzyme and the reaction runs until equilibrium has been reached, the final concentrations are found to be: glucose-6-phosphate (0.035 mM), glucose (100 mM), and Pi (100 mM). Calculate AG" at 25°C and pH 7. 10:21 PM 4/21/2021 F5 F6 F7 F8 F10 F9 7 8. Backspace ーの

Isomaltose (an isomer of maltose), one of the degradation products of starch is further hydrolyzed into its monosaccharide components prior to its intestinal absorption and entry into the glycolysis. Calculate the no. of ATP molecules produced from the digestion and complete oxidation of 1 molecule of isomaltose considering the glycerol-3-phosphate shuttle. Answer the ff.: a) Total no. of glucose molecules entering glycolysis b) Total no. of pyruvate mols. produced at the end of glycolysis c) Total no. of mitochondrial NADH produced after pyruvate is acted upon by pyruvate dehydrogenase complex d) Total no. of CO2 released right after the pyruvate dehydrogenase complex reaction e) Total no. of acetyl CoA mols. entering the Citric Acid Cycle f) Total no. of net cytosolic ATP mols. produced right after glycolysis g) Total no. of all NADH mols. produced after complete oxidation h) Total no. of all FADH2 mols. produced after complete oxidation i) Total no. of all mitochondrial…
Draw the products of the reaction of xylulose-5-phosphate and erythrose-4-phosphate catalyzed by transketolase in the pentose phosphate pathway. Provide the structure in the protonation state found in physiological conditions. H H H OH FO HO-H H-OH H OPO3²- Q transketolase Draw glyceraldehyde-3- phosphate H H- H H H O OH OH OPO3²- Draw fructose-6- phosphate Q I I
The ΔG°’ for the aldolase reaction of glycolysis in muscle is +22.8 kJ/mol. Why does the aldolase reaction proceed in the direction of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate during glycolysis?
The standard state free energy change for Step 4 of glycolysis (where an aldolase enzyme splits fructose 1,6-bisphosphate into GAP and DHAP) is +23.8 kJ/mol. Yet, glycolysis still proceeds spontaneously in the vast majority of cells. Why does this step in particular proceed spontaneously under typical cellular conditions?
Draw OUT THE arrow pushing reaction mechanism for the following steps of glycolysis: SHOW/IDENTIFY the arrow pushing mechanism in at least 2 steps. CH,OPO CH,OH hexokinase 2+ H H H H H H ОН + ATP OH H ADP + H+ H ОН + НО HO OH H ОН H ОН Glucose-6-phosphate (G6P) Glucose
Although both hexokinase and phosphofructokinase catalyze irreversible steps in glycolysis and the hexokinase-catalyzed step is first, phosphofructokinase is nonetheless the pacemaker of glycolysis. What does this information tell you about the fate of the glucose 6-phosphate formed by hexokinase? Glucose 6-phosphate must be unstable and release its phosphoryl group over time. Glucose 6-phosphate must be utilized by other metabolic pathways. Glucose 6-phosphate must allosterically inhibit phosphofructokinase, but not hexokinase. Glucose 6-phosphate must be wasted when it is produced in excess.
In the third step of glycolysis, the given reactions are coupled. reaction 1: fructose-6-phosphate + Pi ⟶ fructose-1,6-bisphosphate + H2O (Δ? = −28 kJ/mol) reaction 2: ATP + H2O ⟶ ADP + Pi (Δ? = +13.8 kJ/mol) Calculate the overall ΔG (kJ/mol) for the coupled reaction.

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