BIO Chapter 8 Review Questions

A
Explanation: A. The products have lower Gibbs free energy than the reactants.In an exergonic reaction, the products have lower Gibbs free energy than the reactants. This means that the reaction is energetically favorable, and will tend to occur spontaneously.

C
Explanation: A transition state is a high-energy intermediate that is formed during a chemical reaction. The transition state is the point at which the reactants are in the process of being converted into the products. The transition state is characterized by a higher energy than the reactants, and a lower energy than the products. The transition state is also characterized by a higher entropy than the reactants or products.

D
Explanation: pH affects enzyme-catalyzed reactions in a number of ways. First, protons serve as a substrate for most reactions. This means that the more protons there are, the more reactions can take place. Second, the energy stored in protons is used to drive endergonic reactions. This means that the more protons there are, the more energy is available to drive the reaction. Third, the concentration of protons affects an enzyme's folded structure and reactivity. This means that the more protons there are, the more likely the enzyme is to be active.

The final product of a pathway inhibits the activity of an enzyme early in the same pathway, thus reducing the activity of all subsequent steps in the pathway.
Explanation: Feedback inhibition is a mechanism that regulates metabolic pathways by preventing the production of enzymes that are not needed. This is accomplished by the binding of a small molecule to an allosteric site on an enzyme, which changes the conformation of the enzyme and prevents it from catalyzing a reaction. Feedback inhibition is a important mechanism for regulating metabolism and preventing the build-up of unwanted products.

Reactions proceed when the reactant molecules (the key) fits snugly into the active site of an enzyme (the lock). Fischer's original model assumed that enzymes were rigid; in fact, enzymes are flexible and often change their shape after binding to substrates.
Explanation: The lock and key model of enzyme activity is an outdated model that is no longer supported by scientific evidence. The model suggests that enzymes are specific for a particular substrate, and that the substrate fits into the enzyme like a key fits into a lock. This model is incorrect because it does not take into account the fact that enzymes are flexible and can accommodate different substrates.

D- energy, such as thermal energy in fire, must be provided to overcome the activation energy barrier before the reaction can proceed.
Explanation: If you were to expose glucose to oxygen on your lab bench, you would not expect to see it burn as shown in Figure 8.6 because the reaction is not spontaneous unless an enzyme is added to the substrates.

B- the sugar likely binds to the enzyme and changes its structure to form a functional active site

CH4 + 2 O2 --> CO2 + 2 H2O CH4 will be reduced. O2 will be oxidized. CH4 has highest energy bonds.
Explanation: The redox reaction that occurs when methane (CH4) burns in the presence of oxygen (O2) can be represented by the following chemical equation:CH4 + 2O2 --> CO2 + 2H2OIn this equation, the methane (CH4) is being oxidized to carbon dioxide (CO2), and the oxygen (O2) is being reduced to water (H2O). Of the four molecules that are in this equation, the one with the highest energy bonds is the methane (CH4).