An enzymatic hydrolysis of fructose- \(1-P\) \\[\text { Fructose- } 1-\mathrm{P}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \text { fructose }+\mathrm{P}_{1}\\] was allowed to proceed to equilibrium at \(25^{\circ} \mathrm{C}\). The original concentration of fructose-1-P was \(0.2 \mathrm{M}\), but when the system had reached equilibrium the concentration of fructose-1-P was only \(6.52 \times 10^{-5} \mathrm{M}\). Calculate the equilibrium constant for this reaction and the free energy of hydrolysis of fructose- \(1-P\).

Short Answer

Expert verified
The equilibrium constant of this reaction is 3067.11, while the free energy of hydrolysis for fructose-1-P is -31.76 kJ/mol.

Step by step solution

01

Calculate the change in concentration

The change in concentration for Fructose-1-P is calculated by taking the original concentration and subtracting it from the equilibrium concentration. As Fructose-1-P and water are on the reactant side, the drop in concentration will be as follows: \[ 0.2 M - (6.52 \times 10^{-5} M) = 0.19993548 M \]
02

Calculate the equilibrium constant (Kc)

The equilibrium constant \(K_c\) for this reaction can be calculated by taking the ratio of concentration of products to that of reactants at equilibrium. The concentration of water is essentially constant and hence can be omitted. The concentration of Fructose and P1 is equal to the drop in concentration of Fructose-1-P.\[ K_c = \left([Fructose][P1]\right)/[Fructose-1-P] = (0.19993548/6.52 \times 10^{-5}) = 3067.11\]
03

Calculate the Gibbs free energy (∆G)

ΔG, the Gibbs Free Energy change, can be calculated using the equation\[ ΔG = -RT\ln K_{c} \]where R is the gas constant (8.314 J K-1 mol-1), T is the temperature in Kelvin (25°C = 298.15K), and Kc is the equilibrium constant. Plugging in these values gives:\[ ΔG = -(8.314J K^{-1} mol^{-1})(298.15K)\ln(3067.11) = -31760.61 J/mol = -31.76 kJ/mol \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Equilibrium Constant
Understanding the equilibrium constant is essential in the study of chemical reactions, especially in biochemical processes like the enzymatic hydrolysis of fructose-1-phosphate. It quantifies the relative concentrations of reactants and products in a reaction at equilibrium. In a general sense, if the equilibrium constant, denoted as \(K_{c}\), is high, the reaction favors the formation of products, while a low \(K_{c}\) indicates that the reactants are more favored.

When calculating \(K_{c}\), it is important to note that the concentrations of solids and pure liquids don't change during a reaction and thus are often omitted from the equation. In the case of fructose-1-phosphate hydrolysis, the water concentration remains relatively constant due to its large excess, allowing us to exclude it from the calculations. The change in concentration of fructose-1-P from its initial state to equilibrium was used to deduce the concentrations of the resulting fructose and phosphate. The equilibrium constant can then be calculated using these concentrations.
Gibbs Free Energy
Gibbs free energy, represented as \(\Delta G\), is a central concept in biochemical thermodynamics. It provides invaluable insights into the spontaneity and energy changes of a chemical reaction. A negative \(\Delta G\) value suggests the reaction can occur spontaneously under constant pressure and temperature.

By using the calculated equilibrium constant, we can determine the Gibbs free energy of the hydrolysis reaction. The relationship between \(\Delta G\) and \( K_{c} \) is expressed using an equation that incorporates the gas constant \(R\) and temperature \(T\) in Kelvin. For the hydrolysis of fructose-1-phosphate, the \(\Delta G\) was found to be negative, indicating that the reaction is exergonic, thus capable of proceeding spontaneously under standard conditions.
Biochemical Thermodynamics
Biochemical thermodynamics allows us to predict the direction and extent of biochemical reactions. It combines principles from both biology and physical chemistry to explain how biological systems adhere to the laws of energy conservation and transformation.

In this context, principles like the equilibrium constant and Gibbs free energy are crucial. Both these quantities reflect how biological molecules like fructose-1-phosphate behave in aqueous environments, such as within our cells. Understanding these principles, any student can gain a deeper comprehension of how energy is channeled through metabolic pathways, like the hydrolysis of fructose-1-phosphate.
Enzyme Kinetics
Enzyme kinetics is the study of the rates at which enzymes catalyze reactions. It seems tangential but is intimately related to biochemical thermodynamics. While our focus might be on the equilibrium state, understanding enzyme kinetics provides us with insights into how quickly that state is reached.

An enzyme's efficacy is characterized by parameters such as the Michaelis constant \(K_m\) and maximum rate \(V_{max}\). These kinetic values can also influence the pathway and rate at which a reaction, like the hydrolysis of fructose-1-phosphate, approaches equilibrium. Although kinetics were not directly calculated in this exercise, the underlying principles remain important for students studying enzymatic reactions and their efficiency in biological systems.

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Most popular questions from this chapter

For the process \(A \equiv B, K_{c g}(A B)\) is 0.02 at \(37^{\circ} \mathrm{C}\). For the process \(\mathrm{B} \rightleftharpoons \mathrm{C}, K_{\mathrm{eq}}(\mathrm{BC})=1000\) at \(37^{\circ} \mathrm{C}\) a. Determine \(K_{\mathrm{rg}}(\mathrm{AC}),\) the equilibrium constant for the overall process \(A \rightleftharpoons C,\) from \(K_{c q}(A B)\) and \(K_{c g}(B C)\) b. Determine standardstate free energy changes for all three processes, and \(\mathrm{us}=\Delta G^{\circ}(\mathrm{AC})\) to determine \(K_{\mathrm{rg}}(\mathrm{AC}) .\) Make sure that this value agrees with that determined in part a of this problem.

Consider carbamoyl phosphate, a precursor in the biosynthesis of pyrimidines: Based on the discussion of high-energy phosphates in this chapter, would you expect carbamoyl phosphate to possess a high free energy of hydrolysis? Provide a chemical rationale for your answer.

The standard-state free energy of hydrolysis for acetyl phosphate is \\[ \begin{aligned} \Delta G^{\circ}=-42.3 \mathrm{kJ} / \mathrm{mol} \\ \text { Actyl-P }+\mathrm{H}_{2} \mathrm{O} \longrightarrow \text { acctate }+\mathrm{P}_{\mathrm{i}} \end{aligned} \\] Calculate the free energy change for acetyl phosphate hydrolysis in a solution of \(2 \mathrm{m} M\) acctate, \(2 \mathrm{m} M\) phosphate, and \(3 \mathrm{n} M\) acetyl phosphate.

The acyl-Co.A synthetase reaction activates fatty acids for oxidation in cells: \\[ \mathrm{R}-\mathrm{COO}^{-}+\mathrm{CaASH}+\mathrm{ATP} \longrightarrow \mathrm{R}-\mathrm{COSCOA}+\mathrm{AMP}+\text { pyrophosphate } \\] The reaction is driven forward in part by hydrolysis of ATP to AMP and pyrophosphate. However, pyrophosphate undergoes further cleavage to yield two phosphate anions. Discuss the energetics of this reaction both in the presence and absence of pyrophosphate cleavage.

You are studying the various components of the venom of a poisonous lizard. One of the venom components is a protein that appears to be temperature sensitive. When heated, it denatures and is no longer toxic. The process can be described by the following simple equation: \\[ \mathbf{T}(\text { toxic }) \rightleftharpoons \mathrm{N} \text { (nontoxic) } \\] There is only enough protein from this venom to carry out two equilibrium measurements. At \(298 \mathrm{K}\), you find that \(98 \%\) of the protein is in its toxic form. However, when you raise the temperature to \(320 \mathrm{K},\) you find that only \(10 \%\) of the protein is in its toxic form. a. Calculate the equilibrium constants for the T to N conversion at these two temperatures. b. Use the data to determine the \(\Delta H^{\circ}, \Delta S^{\circ},\) and \(\Delta G^{\circ}\) for this process.

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