Chapter 3 Quiz

Consider two molecules that associate with each other through hydrogen bonds. The larger the equilibrium constant, K, for this association: A. the more tightly the two molecules will bind. B. the less tightly the two molecules will bind.

A. the more tightly the two molecules will bind.

The G° of the hydrolysis reaction of ATP is -7.3 kcal/mole, but in a cell the actual G is much more negative because: A. ATP is much higher in concentration than the products ADP and Pi. B. ATP is much lower in concentration than the products ADP and Pi.

A. ATP is much higher in concentration than the products ADP and Pi.

Which of the following results in increased disorder? A. Dissolving salt in water B. Joining two sugars to make a sucrose molecule C. Compressing a spring to a tense state

A. Dissolving salt in water

Which energy conversion characterizes photosynthesis? A. Electromagnetic (light) energy → chemical bond energy B. Electromagnetic (light) energy → heat energy C. Electromagnetic (light) energy → kinetic energy

A. Electromagnetic (light) energy → chemical bond energy

In thermodynamics, what does the term "free energy" refer to? A. Energy that can be harnessed to do work or drive chemical reactions B. Excess energy from a reaction that a cell does not use C. Energy required to initiate a chemical reaction

A. Energy that can be harnessed to do work or drive chemical reactions

Consider the reaction A + B → AB. How is the equilibrium constant expressed for this reaction with two substrates and a single product? A. K = [AB]/[A][B] B. K = [A][B]/ [AB] C. K = ([A] + [B])/ [AB]

A. K = [AB]/[A][B]

Activated carriers that transfer methyl, carboxyl, and glucose groups for the purpose of biosynthesis are typically generated in reactions coupled to ATP hydrolysis. A. True B. False

A. True

An enzyme can lower the activation energy of a reaction. A. True B. False

A. True

Energetically favorable reactions are those that create disorder by decreasing the free energy of the system to which they belong. A. True B. False

A. True

Energetically unfavorable reactions can occur if they are coupled to a second reaction with a negative /δ∊λτα Gso large that the net /δ∊λτα Gof the entire process is negative. A. True B. False

A. True

In cells, small molecules can diffuse over short distances quickly. A. True B. False

A. True

In isolation, the formation of an activated carrier molecule, such as ATP, NADH, or NADPH, is an energetically unfavorable reaction. A. True B. False

A. True

The free energy change (G) and the standard-free energy change(G°) of a reaction differ in that G depends on the concentrations of the molecules in the reaction, whereas for G°, the concentrations are set to a fixed value. A. True B. False

A. True

The overall free-energy change for coupled reactions is equal to the sum of the free-energy changes for each individual reaction. A. True B. False

A. True

When an enzyme lowers the activation energy for the forward reaction X → Y, it also lowers the reaction rate for the reverse reaction Y → X by the same amount. A. True B. False

A. True

For the simple reaction Y → X, the equilibrium constant K is: A. [X]/[Y] B. [Y]/[X] C. [X]*[Y] D. [Y]*[X]

A. [X]/[Y]

Chemical reactions proceed spontaneously only in the direction that: A. leads to a loss of free energy. B. leads to a gain of free energy. C. leads to an increase in orderliness.

A. leads to a loss of free energy.

Two molecules will bind to each other by means of noncovalent bonds if the G° of the interaction is: A. negative (the free energy of the product is lower than the sum of the free energies of the unbound partners). B. zero (the free energy of the product is the same as the sum of the free energies of the unboundpartners). C. positive (the free energy of the product is higher than the sum of the free energies of the unbound partners).

A. negative (the free energy of the product is lower than the sum of the free energies of the unbound partners).

A reaction occurs spontaneously only if the change in free energy G is: A. negative. B. zero. C. positive.

A. negative.

The rate at which an enzyme will encounter its substrate depends on: A. the concentration of the substrate. B. the concentration of other proteins in the cytosol. C. the viscosity of the cytosol. D. the size of the enzyme.

A. the concentration of the substrate.

In an enzyme catalyzed reaction, a low value of KM indicates that a substrate binds: A. very tightly to the enzyme. B. very weakly to the enzyme.

A. very tightly to the enzyme.

For every 1.42 kcal/mole difference in free energy at 37°C, K changes by a factor of: A. 10-1. B. 10. C. 102. D. 103.

B. 10.

What is the term for the extra energy boost required to initiate an energetically favorable reaction? A. Free energy B. Activation energy C. Potential energy

B. Activation energy

Which is NOT true of a reaction at chemical equilibrium? A. /delta G is equal to zero. B. Both the forward and reverse reactions have completely stopped. C. The rates of the forward and reverse reactions are equal.

B. Both the forward and reverse reactions have completely stopped.

What is the measure of disorder in a system called? A. Free energy B. Entropy C. Enthalpy

B. Entropy

Which statement about enzymes is NOT true? A. Enzymes can speed up energetically favorable reactions. B. Enzymes can force reactions to occur that are overall energetically unfavorable. C. Enzymes can help build highly ordered structures. check my answer

B. Enzymes can force reactions to occur that are overall energetically unfavorable.

After an enzyme catalyzes a reaction, the enzyme has been consumed and cannot perform additional reactions. A. True B. False

B. False

Because they generate order (by surviving, growing and forming complex communities), living cells defy the second law of thermodynamics. A. True B. False

B. False

The formation of ATP can be coupled to energetically unfavorable reactions to allow them to proceed. A. True B. False

B. False

Which of the following statements is NOT true? A. NADPH is an activated carrier molecule that is usually used in biosynthetic reactions to build energy-rich molecules. B. NADPH is an activated carrier molecule that is used primarily by plants. C. NADH is an activated carrier molecule that is usually used in oxidation reactions to produce ATP.

B. NADPH is an activated carrier molecule that is used primarily by plants.

What is the origin of the energy that animals acquire by eating plants or other animals? A. Heat B. Sunlight C. Sugars

B. Sunlight

Which of the following does NOT follow the first law of thermodynamics? A. The conversion of sunlight into energy stored in chemical bonds during photosynthesis B. The use of heat to burn foodstuff inside cells C. The metabolism of nutrients in order to produce energy

B. The use of heat to burn foodstuff inside cells

In both plants and animals, the process of "controlled burning" that extracts energy from food molecules is a process of gradual: A. hydrolysis. B. oxidation. C. reduction.

B. oxidation.

Which of the following represents energy in its most disordered form? A. Electromagnetic (light) energy B. Chemical bond energy C. Heat energy

C. Heat energy

Which of the following statements is NOT true? A. Oxidation and reduction reactions always occur simultaneously. B. When a sugar molecule is oxidized to CO2 and H2O, O2 molecules are reduced. C. Hydrogenation reactions are oxidations, and dehydrogenation reactions are reductions.

C. Hydrogenation reactions are oxidations, and dehydrogenation reactions are reductions.

.What is the difference between NAD+ and NADH? A. NADH carries an extra phosphate group. B. NADH is the oxidized form, while NAD+ is the reduced form. C. NADH carries an extra proton and two high-energy electrons.

C. NADH carries an extra proton and two high-energy electrons.

Which of the following is true? A. NADPH loses a phosphate group to form NADH during biosynthetic reactions. B. NADPH and NADH deliver electrons to the same set of enzymes. C. NADPH and NADH are used in independent pathways in cells. D. NADH caries electrons in animal calls and NADPH does the same in plants.

C. NADPH and NADH are used in independent pathways in cells.

Which of the following does not describe oxidation? A. The addition of oxygen atoms to a molecule B. The removal of electrons from a molecule C. The conversion of a chlorine atom to Cl-

C. The conversion of a chlorine atom to Cl-

Which statement is true about the breakdown of polymers? A. The reaction occurs without the need of enzymes. B. The reaction is energetically unfavorable. C. The reaction is associated with a negative change in free energy.

C. The reaction is associated with a negative change in free energy.

Which statement is true about the removal of a terminal phosphate from ATP? A. The reaction is a condensation reaction. B. The reaction is associated with a positive change in G°. C. The reaction is energetically favorable.

C. The reaction is energetically favorable.