The phosphorylation of glucose to glucose 6-phosphate is the initial step in the catabolism of glucose. The directphosphorylation of glucose by P, is described by the equationGlucose + P→ glucose 6-phosphate + H₂O AG 13.8 kJ/mol=Coupling ATP hydrolysis to glucose phosphorylation makes thermodynamic sense, but consider how the coupling mighttake place.Given that coupling requires a common intermediate, one conceivable mechanism is to use ATP hydrolysis to raise theintracellular concentration of P₁. The increase in P; concentration would drive the unfavorable phosphorylation of glucose by P₁. Is increasing the P; concentration a reasonable way to couple ATP hydrolysis and glucose phosphorylation?Yes. Increasing the concentration of P; would decrease K'eq and shift equilibrium to the right.No. The phosphate salts of divalent cations would be present in excess and precipitate out.No. The extra P; would give a negative AG", but would give a positive AG.Yes. The extra ATP hydrolysis would provide enough free energy to drive the phosphorylation reaction.In hepatocytes, the enzyme glucokinase catalyzes the ATP-coupled phosphorylation of glucose. Glucokinase binds both ATPand glucose, forming a glucose-ATP-enzyme complex. The enzyme then transfers the phosphoryl group directly from ATPto glucose.Select the advantages of phosphoryl group transfer compared to hydrolysis and subsequent phosphorylation?Glucokinase increases the transition state energy, favoring glucose phosphorylation.Reaction intermediates do not need to be present in excess.The process takes advantage of the high phosphoryl group transfer potential of ATP.ATP hydrolysis is thermodynamically unfavorable compared to group transfer.

When considering the phosphorylation of glucose to form glucose 6-phosphate, we have:The standard…

Answered: Is increasing the P; concentration a…

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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Consider the following list of phosphorylated compounds with their free energy changes of phosphate hydrolysis: Glucose-1-phosphate (-5.0 kcal/mol), PEP (-14.8 kcal/mole), 1,3-bisphosphoglycerate (-11.8 kcal/mole) and Glucose-6-Phosphate (-3.3 kcal/mol). Given that the free energy change of ATP hydrolysis is -7.3 kcal/mole, which of these molecules be directly synthesized by the transfer of a phospho- group from ATP? 1,3-bisphosphoglycerate Glucose-6-phosphate All of those phosphorylated compounds. PEP Glucose-1-phosphate
What terms would best describe the above coupled reaction? (If the DGo for ATP hydrolysis into ADP + inorganic phosphate is -7.3 kcal/mole, and the DGo for maltose synthesis from glucose + glucose is +3.7 kcal/mole, calculate the standard free energy change for the combined reaction of ATP + glucose + glucose g ADP + maltose + inorganic phosphate.) it is non-spontaneous and endothermic (because the overall DGo is negative) it is spontaneous and exothermic (because the overall DGo is negative) it is non-spontaneous and endothermic (because the overall DGo is positive) it is spontaneous and exothermic (because the overall DGo is positive) it is non-spontaneous and exothermic (because the overall DGo is negative)
Assume that in a certain cell, the ratio of products/reactants or Keg = 809.5 (Keq is dimensionless) for the reaction Glucose + 2ATP > Glucose-1,6-diP + 2ADP, at a particular instant, the concentrations of each compound were Glucose =2.4M, ATP =11.1M, ADP -12.8M and G-6-P -28.4M. Calculate the difference (dimensionless) between Keq and the ratio of products/ractants at this instance, in this cell, to five decimal places
Free energy changes under intracellular conditions differ markedly from those determined under standard conditions. AG" =-30.5 kJ/mol for ATP hydrolysis to ADP and P,. Calculate AG for ATP hydrolysis in a cell at 37 °C that contains [ATP] =3 mM, [ADP] =1mM, and [P] =1 mM.
The first reaction in glycolysis is the phosphorylation of glucose: Pi + glucose → glucose-6-phosphate + H2O This is a thermodynamically unfavorable process, with ∆G°′ = +13.8 kJ/mol. (a) In a liver cell at 37 °C the concentrations of both phosphate and glucose are normally maintained at about 5 mM each. What would be the equilibrium concentration of glucose-6-phosphate, according to the above data? (b) This very low concentration of the desired product would be unfavorable for glycolysis. In fact, the reaction is coupled to ATP hydrolysis to give the overall reaction ATP + glucose → glucose-6-phosphate + ADP + H+ What is ∆G°′ for the coupled reaction? (c) If, in addition to the constraints on glucose concentration listed previously, we have in the liver cell ATP concentration = 3 mM and ADP concentration = 1 mM, what is the theoretical concentration of glucose6-phosphate at equilibrium at pH = 7.4 and 37 °C? The answer…
Coupled reactions occur where a nonspontaneous reaction is enabled by coupling it to a spontaneous reaction. This approach is common in biological settings. Determine if ATP could be generated by this biochemical reaction. You have calculated that cell potential is +0.637V. An example of a coupled reaction is the first step of glycolysis, the phosphorylation of glucose to form glucose-6-phosphate shown below. The net ∆Gº for this reaction is
The formation of glutamine from glutamate and ammonium ions requires 14.2 kJ mol-1 of energy input. It is driven by the hydrolysis of ATP to ADP mediated by the enzyme glutamine synthetase. {a) Given that the change in Gibbs energy for the hydrolysis of ATP corresponds to ΔG = -31 kJ mol-1, under the conditions prevailing in a typical cell , can the hydrolysis drive the formation of glutamine? (b) What amount {in moles) of ATP must be hydrolysed to form 1 mol glutamine? (c) Suppose that the radius of a typical cell is 10 μm and that inside it 106 ATP molecules are hydrolysed each second. What is the power density of the cell in watts per cubic metre (1W = 1 Js- 1)? (d) A computer battery delivers about 15 Wand has a volume of 100 cm3 Which has the greater power density, the biological cell or the battery?
Calculate the standard free-energy change of the reaction catalysed by the enzyme phosphoglucomutase Glucose- 1-P = Glucose-6-P, given that, starting with 28.29 mM Glucose-1-P and no Glucose-6-P, the final equilibrium mixture at 25°C and pH=7.0 contains 9.77 mM Glucose-6-P and the remaining Glucose- 1-P. Give the answer in J/mol.K to one decimal place.
Inside cells, the AG value for the hydrolysis of ATP to ADP + Pi is approximately -50 kJ/mol (-12 kcal/mol). Calculate the approximate ratio of [ATP] to [ADP][Pi ] in cells at 37°C. AG = AG + RT InKe R= 8.315 x 10³ kJ mol deg T= 298 K Table 15.1 Standard free energies of hydrolysis of some phosphorylated compounds Compound kJ mol- kcal mol- Phosphoenolpyruvate 1,3-Bisphosphoglycerate Creatine phosphate ATP (to ADP) -61.9 -14.8 -49.4 -11.8 -43.1 -10.3 -30.5 - 7.3 - 5.0 Glucose 1-phosphate Pyrophosphate Glucose 6-phosphate -20.9 -19.3 -4.6 -13.8 3.3 Glycerol 3-phosphate - 9.2 2.2 biochemistry
Explain why the glycogen phosphorylase reaction (ΔG°′= 3.1 kJ · mol−1) is exergonic in the cell.
The first reaction in Glycolysis is the phosphorylation of Glucose:Pi + Glucose → Glucose 6-Phosphate + waterThis is a thermodynamically unfavorable process with a ∆G0’ = +13.8 kJ/mol. In a liver cell at370C the concentrations of both phosphate and glucose are normally maintained at about 0.005 M each. What would be the equilibrium concentration of Glucose 6-Phosphate according to the above data? Note: In the biochemical standard state [H2O] = 1.0 a. 0.00000012 b. 0.0000025 c. 0.00000025 d. 0.00474 e. 0.005 f. 1.0 g. 0.1 h. 0.25 i. 2.4
The first reaction in Glycolysis is the phosphorylation of Glucose:Pi + Glucose → Glucose 6-Phosphate + waterThis is a thermodynamically unfavorable process with a ∆G0’ = +13.8 kJ/mol. In a liver cell at370C the concentrations of both phosphate and glucose are normally maintained at about 0.005 M each. What would be the equilibrium concentration of Glucose 6-Phosphate according to the above data? Note: In the biochemical standard state [H2O] = 1.0 (this will help with the question below) When the reaction described in question number 3 is coupled to the hydrolysis of ATP the equilibrium concentration of Glucose 6-Phosphate goes to: a. 10.5 b. 350 c. 3000 d. 77 e. 4.5 f. 55 g. 550 h. 652 i. 1120

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