The pH of plasma is regulated by the following equilibria: 

According to Le Chatlier's Principle, when the concentration of protons increases (plasma becomes acidic) the equilibrium shift will be to the left of the equation. Therefore, there will be an initial increase of carbon dioxide. However, the body needs to rid itself of the excess carbon dioxide. This happens via hyperventilation - the increased breathing out of carbon dioxide.

Less carbon dioxide in the lungs from the constant exhalation will cause the decrease in the hydrogen ion concentration in the blood, resulting in a rise in pH.

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. 

The Gibbs Free Energy ()of a reaction tells us whether or not the reaction is favorable. A favorable reaction is also known as spontaneous, and has a negative . A non-favorable reaction is non-spontaneous, and has a positive . The term exergonic (meaning energy exits the system) is also used for a reaction with a negative , while the term endergonic (meaning energy enters the system) is used for a reaction with a positive . Therefore, a reaction with  is both exergonic and spontaneous. 

Gibbs Free Energy () is a thermodynamic principle that tells us about only about the spontaneity of a reaction (whether or not the reaction will occur). On the other hand, the rate of a reaction can be described by chemical kinetics. The question gives no information about the kinetics of the reaction, and we therefore cannot draw any conclusions about the rates of the two reactions described.

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.

The G values given in the question relate to the reactions' thermodynamics. A negative G value means that a reaction is thermodynamically spontaneous. A spontaneous reaction can occur without further energy input. This does not tell us anything about the reaction's rate (kinetics). A spontaneous reaction may be slow or it may be fast. 

A catalyst lowers the activation energy of a reaction. This could be accomplished through stabilization of the transition state by lowering its energy. A catalyst does not change the free energy difference between products and reactants, so no change in G of the reaction is observed.

This question is asking us to determine what effect a pH change would have on the reaction in which ATP is hydrolyzed into ADP. First, we have to realize that if pH were lowered, that means we are dealing with a more acidic solution. A more acidic solution, in turn, means that we have an increased concentration of . So, in essence, the question is asking what effect an increased  concentration will have on the reaction. In the reaction, we can see that  is on the product side of the reaction (on the right side). Therefore, if we drive the  concentration up, the reaction will be pushed toward the left according to Le Chatelier's principle. Furthermore, it's important to note that changing the concentration of any of the reactants or products will not have an effect on the equilibrium constant, . In fact, it is precisely because the equilibrium constant doesn't change that the reaction will shift to the left, so that the constant will remain just that, constant. Moreover, the only thing that can change an equilibrium constant is the temperature at which the reaction takes place.

The Gibbs free energy  becomes less favorable, or more positive, as enthalpy  increases and entropy  decreases.