Many biochemical reactions have positive values for ΔG^∘ and seemingly should not be expected to

step 1 For this question, all we're going to do is sum these two reactions together. The first reaction

Many biochemical reactions have positive values for ΔG^∘ and...

Many biochemical reactions have positive values for $\Delta G^{\circ}$ and seemingly should not be expected to be spontaneous. They occur, however, because they are chemically coupled with other reactions that have negative values of $\Delta G^{\circ}$. An example is the set of reactions that forms the beginning part of the sequence of reactions involved in the metabolism of glucose, a sugar. Given these reactions and their corresponding $\Delta G^{\circ}$ values, $$ \begin{array}{r} \text { glucose }+\mathrm{PO}_{4}^{3-} \longrightarrow \text { glucose } 6 \text { -phosphate }+\mathrm{H}_{2} \mathrm{O} \\ \Delta G^{\circ}=+13.13 \mathrm{~kJ} \end{array} $$ calculate $\Delta G^{\circ}$ for the coupled reaction glucose $+\mathrm{ATP} \longrightarrow$ glucose 6 -phosphate $+\mathrm{ADP}$

Many biochemical reactions have positive values for $\Delta G^{\circ}$ and seemingly should not be expected to be spontaneous. They occur, however, because they are chemically coupled with other reactions that have negative values of $\Delta G^{\circ}$. An example is the set of reactions that forms the beginning part of the sequence of reactions involved in the metabolism of glucose, a sugar. Given these reactions and their corresponding $\Delta G^{\circ}$ values,
$$
\begin{array}{r}
\text { glucose }+\mathrm{PO}_{4}^{3-} \longrightarrow \text { glucose } 6 \text { -phosphate }+\mathrm{H}_{2} \mathrm{O} \\
\Delta G^{\circ}=+13.13 \mathrm{~kJ}
\end{array}
$$
calculate $\Delta G^{\circ}$ for the coupled reaction glucose $+\mathrm{ATP} \longrightarrow$ glucose 6 -phosphate $+\mathrm{ADP}$

Key Concepts

Gibbs Free Energy

Gibbs free energy is a thermodynamic quantity that predicts the direction of chemical reactions and indicates whether a reaction can occur spontaneously under constant temperature and pressure. Its value, denoted as ?G, is used to assess the balance between the enthalpy change and the entropy change for a reaction.

Standard Free Energy Change (?G°)

Standard free energy change, ?G°, refers to the Gibbs free energy change of a reaction when all reactants and products are in their standard states (typically 1 M concentrations for solutes, 1 atm pressure for gases, and pure substances in standard states). It provides a reference point for comparing the relative spontaneity of reactions under defined conditions.

Chemical Reaction Coupling

Chemical reaction coupling is the process of linking a non-spontaneous reaction (with a positive ?G°) to a spontaneous one (with a negative ?G°) so that the overall process becomes thermodynamically favorable. By combining reactions, the energy released from the favorable reaction can drive the unfavorable one, allowing essential biochemical processes to proceed.

ATP Hydrolysis

ATP hydrolysis is a key biochemical reaction where adenosine triphosphate (ATP) is converted to adenosine diphosphate (ADP) and inorganic phosphate, releasing energy. This reaction is typically exergonic and is used to drive many cellular processes by coupling the energy release to endergonic reactions that would otherwise be energetically unfavorable.

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