ΔG |
– unfavorable reaction – endergonic |
-ΔG |
– spontaneous reaction – exergonic |
ΔH |
– products have higher potential energy – unfavorable |
-ΔH |
– products have lower potential energy – spontaneous |
ΔS |
– products are more disordered than reactants – spontaneous |
-ΔS |
– products are more ordered than reactants – unfavorable |
When is the overall free energy change ΔG in a reaction most likely to be negative (meaning that the reaction is exergonic)? A. When products have lower potential energy and higher entropy than reactants |
A. When products have lower potential energy and higher entropy than reactants |
Electrons tend to have more potential energy when ____. A. they are in electron shells close to the nucleus |
C. they are in electron shells far from the nucleus |
The total energy in a molecule, its enthalpy, is given by the letter ____. A. H |
A. H |
Under what conditions could some exothermic (ΔH<0) reactions be nonspontaneous (ΔG>0)? a. The overall reaction results in an increase in entropy (products have greater entropy than reactants). |
d. The overall reaction reduces entropy (products have less entropy than reactants). |
For living organisms, which of the following is an important consequence of the first law of thermodynamics? a. The entropy of an organism decreases with time as the organism grows in complexity. |
e. The organism ultimately must obtain all of the necessary energy for life from its environment. |
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics? A. Living organisms are able to transform energy into entropy. B. As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth. C. Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe. D. Living organisms do not follow the laws of thermodynamics. E. Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time. |
B. As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth. |
Which of the following statements is a logical consequence of the second law of thermodynamics? A. Every chemical reaction must increase the total entropy of the universe. |
A. Every chemical reaction must increase the total entropy of the universe. |
The mathematical expression for the change in free energy of a system is ΔG =ΔH – TΔS. Which of the following is (are) correct? A. ΔH is the change in entropy, the energy available to do work. |
C. ΔG is the change in free energy. |
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions? A. α -phosphate (the phosphate closest to ribose) |
C. γ-phosphate (the terminal phosphate) |
Which term describes the degree to which an element attracts electrons? A. Oxidation. |
C. Electronegativity |
Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other? A. Ionic and covalent. |
B. Anion and cation. |
Which of the following statements is true of the bonds in a water molecule? A. Oxygen acts as the electron acceptor and is oxidized. |
D. Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero. |
Which of the following statements is not true of most cellular redox reactions? A. The electron acceptor is reduced. |
B. A hydrogen atom is transferred to the atom that loses an electron. |
Gaseous hydrogen burns in the presence of oxygen to form water: 2H₂ + O₂ → 2H₂O + energy Which molecule is oxidized and what kind of bond is formed? A. Hydrogen, polar. |
A. Hydrogen, polar. |
How do cells use ATP to raise the energy level of reaction substrates? A. ATP is hydrolyzed to release its energy. |
C. The terminal phosphate of ATP is bound to the substrate. |
Why is ATP a good source of energy for biological reactions? A. Peroxide links are highly reactive. |
D. Triphosphate chains are unstable. |
A reaction is said to be unfavorable if … A. t will be very slow without a catalyst. |
E. Both (b) and (c). |
The reaction A → B is unfavorable by itself, but through energy-coupling, cells can use ATP to convert A into B. How is this done? A. Hydrolysis of ATP releases heat that is used by the unfavorable reaction. |
C. The unfavorable reaction is replaced by two favorable reactions. |
How do cells replace the energy-rich ATP that is destroyed in energy-coupled reactions? A. Chloroplasts use light energy to synthesize ATP. |
D. Both (a) and (b). |
Which statement most accurately explains why ATP hydrolysis is highly exergonic? A. There is a large increase in potential energy because charge repulsion is reduced. |
D. There is a large drop in potential energy because charge repulsion is reduced |
Which statement is true for all redox reactions? A. An atom or molecule loses one or more electrons via reduction. |
B. They involve the transfer of electrons. |
Redox reactions involve the gain or loss of _____. A. neutrons |
C. electrons |
When ATP is hydrolyzed into ADP and inorganic phosphate, _____. A. a redox reaction has occurred |
C. free energy is released |
Which statement is true of enzymes? A. Enzymes can be either proteins or RNA molecules. |
E. (a), (b), and (c). |
How can "induced fit" influence the specificity of an enzyme? A. It can not influence the specificity of an enzyme. |
D. Both (b) and (c). |
Enzymes speed reactions mainly by … A. protecting the catalysts. |
B. lowering EA |
Which fact is most important in explaining how enzymes speed reactions? A. Large molecules collide more energetically than small molecules. |
B. High-energy collisions are less common than low-energy collisions. |
Can an enzyme make a nonspontaneous reaction occur spontaneously? Why or why not? A. No, because enzymes do not lower the activation energy of the reaction. |
B. No, because enzymes do not affect the overall ΔG of a reaction. |
How do current models of enzyme function differ from Fischer’s lock-and-key model? A. Contrary to what Fischer thought, we now know that enzymes are catalysts that can catalyze multiple reactions without being consumed. |
D. Rather than enzymes being rigid, we now believe they undergo an induced fit upon substrate binding. |
During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction? A. -40 kcal/mol |
B. -20 kcal/mol |
Which type of control agent never speeds an enzyme’s action? A. Substrate analog |
A. Substrate analog |
Which type of control agent exerts noncompetitive inhibition? A. Substrate analog |
D/ Both (b) and (c). |
In cooperativity, … A. two or more enzymes are needed to bind one control agent. |
D. if one substrate is bound, the next binds more easily. |
Which statement is characteristic of allosteric effectors? A. They bind to the active site. |
C. They may not resemble the enzyme’s substrates. |
When a pathway is subject to allosteric feedback inhibition, … A. the last enzyme in the pathway is allosteric. |
B. an accumulation of effectors slows the pathway. |
Which of the following can change the shape of an enzyme? A. temperature |
D. all of the above |
An enzyme inhibitor that is roughly the same shape as the substrate and binds at the active site is termed a(n) _____ inhibitor. A. allosteric |
B. competitive |
Which of these is an example of negative feedback? A. As a blood clot begins to form, the process of its formation gets faster and faster. |
C. After you eat, insulin stimulates the lowering of blood sugar levels. |
The polymerization of amino acids into a protein is an example of _____. A. an anabolic pathway |
A. an anabolic pathway |
Consider the two-step metabolic pathway: A—(enzyme 1)—>B—(enzyme 2)—>C How would inactivating enzyme 1 affect the concentrations of molecules A, B, and C relative to what they would be if the pathway were fully functional? A. A and B would decrease; C would increase. |
D. A would increase; B and C would decrease. |
What do Competitive Inhibition and Allosteric Regulation have in common? A. Both strategies depend on the concentration of the regulatory molecule. |
A, D, E |
Competitive Inhibition (2) |
1. The regulatory molecule binds at the active site 2. The regulatory molecule is similar in size and shape to the enzymes natural substrate |
Allosteric Regulation (2) |
1. The regulatory molecule binds away from the active site 2. The regulatory molecule changes the shape of the enzyme |
Catabolic Reaction |
breaks down products to generate a product that a cell might need |
Anabolic Reaction |
synthesizes a product to be used by the cell |
Catabolic reactions will often have A. a negative ΔG based on a decrease in enthalpy and increase in entropy |
A. a negative ΔG based on a decrease in enthalpy and increase in entropy |
Anabolic reactions will often have A. a positive ΔG based on a decrease in enthalpy and increase in entropy |
D. a positive ΔG based on an increase in enthalpy and decrease in entropy |
Chapter 8 Mastering
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