The standard free energy, AGO, of hydrolysis of inorganic polyphosphate, polyP, is about −20 kJ/mol for each P; released. In acell, it takes about 50 kJ/mol of energy to synthesize ATP from ADP and Pi.○POInorganic polyphosphate (polyP)Is it feasible for a cell to use polyP to synthesize ATP from ADP? Why or why not?No. The reaction is unidirectional and always proceeds in the direction of polyP synthesis from ATP.Yes. If [ADP] and [polyP] are kept high, and [ATP] is kept low, the actual free-energy change would be negative.No. The synthesis of ATP from ADP and P; has a large positive G'o compared to polyP hydrolysis.Yes. The hydrolysis of polyP has a sufficiently negative AG to overcome the positive AGO of ATP synthesis.Correct Answer

The feasibility of the reaction depends on the Gibbs free energy change (ΔG), which is influenced by…

Answered: The standard free energy, AGO, of…

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter27: Metabolic Integration And Organ Specialization

Section: Chapter Questions

Problem 20P: Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy...

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Figure 27.3 illustrates the response of R (ATP-regenerating) and U (ATP-utilizing) enzymes to energy charge. a. Would hexokinase be an R enzyme or a U enzyme? Would glutamine: PRPP amidotransferase, the second enzyme in purine biosynthesis, be an R enzyme or a U enzyme? b. If energy charge = 0.5: Is the activity of hexokinase high or low? Is ribose-5-P pyrophosphokinase activity high or low? c. If energy charge = 0.95: Is the activity of hexokinase high or low? Is ribose-5-P pyrophosphokinase activity high or low?
The Reactions and Meehanisms of the Leloir Pathway Write the reactions that permit galactose to be utilized in glycolysis. Write a suitable mechanism, tor one of these reactions.
Energetic of Fructose-1 ,6-bis P Hydrolysis (Integrates with Chapter 3.) The standard free energy change (G) for hydrolysis of fructose-1. 6-bisphosphate (FBP) to fructose-S-phosphate (F-6-P) and P: is -16.7 KJ/mol: FBP + H2O fructose-6-P + Pi The standard free energy change (G) for ATP hydrolysis is -30.5 KJ/mol: ATP + H2O ADP + Pj What is the standard free energy change for the phosphofructokinase reaction: ATP + fructose-6-P ADP + FBP b. What is the equilibrium constant for this reaction? c. Assuming the intracellular concentrations of [ATP] and (ADP] are maintained constant at 4 mM and 1.6 mM, respectively, in a rat liver cell, what will be the ratio of [FBP]/[fructose-6-P] when the phosphofructokinase reaction reaches equilibrium?
The Relative Efficiency of ATP Synthesis in Noncyclic versus Cyclic Photophosphorylation If noncyclic photosynthetic electron transport leads to the translocation of 7 H+/2e- and cyclic photosynthetic electron transport leads to the translocation of 2 H+/e-, what is the relative photosynthetic efficiency of ATP synthesis (expressed as the number of photons absorbed per ATP synthesized) for noncyclic versus cyclic photophosphorylation? (Assume that the CF1CF0-ATP synthase yields 3 ATP/14 H+.)
Effects of Changing Metabolite Concentrations on Glycolysis In an erythrocyte undergoing glycolysis what would be the effect of a sudden increase in the concentration of a. AÎ¤P? b. AMP? c. fructose-1.6-bisphosphate? d. fructose-2, 6-bisphosphate? e. citrate? f. glucose-6-phospthate?
Based on your residing of this chapter, what would you expect to be the most immediate effect oil glycolysis, if the steady-state concentration of gJucose-6-P were 8.3 mM instead of 0.083 mM?
Distinguishing the Mechanisms of Class I and Class I Aldolases Fructose bisphosphate aldolase in animal muscle is a class 1 aldolase, which forms a Schiff base intermediate between substrate (for example. fructose-1, 6-bisphosphate or dihydroxyacetone phosphate) and a lysine at the active site (see Figure I8.12). The chemical evidence for this intermediate conies from studies with aldolase and the reducing agent sodium borohydride, NaBH4. Incubation of the enzyme with dihydroxyacetone phosphate and NaBH4 inactivates the enzyme. Interestingly, no inactivation is observed if NabH4 is added to the enzyme in the absence of substrate. Write a mechanism that explains these observations and provides evidence for the formation of a Schiff base intermediate in the aldolase reaction.
Using the ActiveModel for aldose reductase, describe the structure of the TIM barrel motif and the structure and location of the active site.
Understanding Enzyme Mechanisms Related to Pyruvate Carboxylase Based on the mechanism for pyruvate carboxylase (Figure 22.3), write reasonable mechanisms for the reactions that follow:
Comparing Glycolysis Entry Points for Sucrose Sucrose can enter glycolysis by either of two routes: Sucrose phosphorylase: Sucrose + Pi fructose + glucose-1-phosphate Invertase: Sucrose + H20 fructose + glucose Would either of these reactions offer Jin advantage over the other In the preparation of hexoses fur entry into glycolysis?
In an enzymatic reaction: a. the enzyme leaves the reaction chemically unchanged. b. if the enzyme molecules approach maximal rate, and the substrate is continually increased, the rate of the reaction does not reach saturation. c. in the stomach, enzymes would have an optimal activity at a neutral pH. d. increasing temperature above the optimal value slows the reaction rate. e. the least important level of organization for an enzyme is its tertiary structure.
Allosteric Regulation of Ribonucleotide Reductase by ATP and Deoxynucleotides Describe the underlying rationale for the regulatory effects exerted on ribonucleotide reductase by ATP, dATP, dTTP, and dGTP.

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