Biochemistry : Thermodynamic Regulation
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Example Questions
Example Question #1 : Thermodynamic Regulation
Which of the following statements are incorrect?
A spontaneous reaction always happens quickly
A spontaneous reaction proceeds in the forward direction with a negative Gibbs free energy value
A spontaneous reaction can still occur with a large decrease in entropy
A nonspontaneous reaction will proceed spontaneously when reversed
A negative enthalpy is favorable for a spontaneous reaction
A spontaneous reaction always happens quickly
The spontaneity of a reaction says nothing about the reaction's speed. For a spontaneous reaction, the change in Gibbs free energy is negative. In other words, the products have lower energy than the reactants. With low temperatures and negative enthalpy, a reaction can still proceed spontaneously if entropy decreases.
Example Question #2 : Thermodynamic Regulation
A reaction has a change in Gibbs free energy (
exergonic and non-spontaneous
endergonic and spontaneous
endergonic and non-spontaneous
Not enough information given.
exergonic and spontaneous
exergonic and spontaneous
The Gibbs Free Energy (
Example Question #2 : Thermodynamic Regulation
What can be said about the rate of a reaction with a 
The rates are equal.
Nothing can be said about reaction rate from the information given.
The rate of the reaction is only faster when the temperature is low.
The rate is faster.
The rate is slower.
Nothing can be said about reaction rate from the information given.
Gibbs Free Energy (
Example Question #3 : Thermodynamic Regulation
In humans, heat is generated by uncoupling oxidative phosphorylation from ATP production during which process?
ATP-hydrolyzing substrate cycles
Sweating
Vasodilation of blood vessels
Metabolism in brown fat cells
ATP hydrolysis during muscle contraction
Metabolism in brown fat cells
The correct answer is "metabolism in brown fat cells." The mitochondria in brown fat have a protein called thermogenin that acts as a proton channel, which allows the dissipation of the proton gradient made by the electron transport chain. This allows oxidative phosphorylation to continue, and produce heat, without the production of ATP. Answers a and b, which both involve ATP hydrolysis, are also used by humans to produce heat but do not involve the uncoupling of oxidative phosphorylation from ATP production. Sweating and vasodilation of blood vessels are both ways that the human body loses heat.
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