The Gibbs free energy change of a reaction can be calculated using the equation ΔG = ΔH – TΔS. A biochemical reaction that can p
rovide energy for cellular metabolism would be one in which: Choose one: A. ΔG was negative. B. all terms on the right are negative. C. ΔG was positive. D. all terms on the right are positive.
The answer is a. ΔG was negative because, for a biochemical reaction to occur and provide energy for cellular metabolism, the Gibbs free energy ΔG = ΔH - TΔS < 0 , for spontaneity. If all terms on the right were to be negative, then ΔG = -ΔH - (-TΔS) = TΔS - ΔH and would only be less than zero if the absolute value of ΔH > absolute value of TΔS. If ΔG was positive as in C, the reaction would not be spontaneous and energy would have to be put into the biochemical reaction for it to occur. If all terms on the right were positive, then, ΔG = ΔH - TΔS < 0 when TΔS > ΔH , else ΔG > 0 and energy would have to be put into the biochemical reaction for it to occur, so its not spontaneous.
A chemical reaction which is associated with a release of energy and thus, is associated with a negative free energy change is said to be an exergonic reaction.
An exergonic reaction owing to the negative free energy change is a spontaneous reaction.
The energy that is released in the exergonic reaction is usually observed in the form of heat and light.
The energy is released due to the breaking of the chemical bonds.
Therefore, on burning of the firewood the bonds between the glucose molecules break up which leads to the release of energy in the form of heat and light and this is thus, an example of an exergonic reaction.
