Question 1

Which of the following is true for anabolic pathways?

Accepted Answer

A)   They do not depend on enzymes.
B)   They are usually spontaneous chemical reactions.
C)   They consume energy to build polymers from monomers.
D)   They release energy as they degrade polymers to monomers. C

Question 2

The ∆G for a particular enzyme-catalyzed reaction is -20 kcal/mol. If the amount of enzyme in the reaction is doubled, what will be the ∆G for the new reaction?

Accepted Answer

A)   -40 kcal/mol
B)   -20 kcal/mol
C)   0 kcal/mol
D)   +20 kcal/mol
E)   +40 kcal/mol B

Question 3

When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?

Accepted Answer

A)   It is used to power yet more cellular work.
B)   It is used to store energy in the form of ATP.
C)   It is used to synthesize ADP.
D)   It is released to the environment. D

Question 4

The ∆G for a particular enzyme-catalyzed reaction is -20 kcal/mol. If the enzyme is removed, what will be the ∆G for the noncatalyzed reaction?

Accepted Answer

A)   -40 kcal/mol
B)   -20 kcal/mol
C)   0 kcal/mol
D)   +20 kcal/mol
E)   +40 kcal/mol

Question 5

Which of the following is true for all exergonic reactions?

Accepted Answer

A)   The products have more total energy than the reactants.
B)   The reaction proceeds with a net release of free energy.
C)   The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants.
D)   A net input of energy from the surroundings is required for the reaction to proceed.

Question 6

Figure 6.3 Activity of various enzymes (a) at various temperatures and (b) at various pH.
-Which curves on the graphs in Figure 6.3 may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot spring at temperatures of 70°C or higher?

Accepted Answer

A)   curves 1 and 5
B)   curves 2 and 4
C)   curves 2 and 5
D)   curves 3 and 4
E)   curves 3 and 5

Question 7

Which of the following is an example of cooperativity?

Accepted Answer

A)   binding of an ATP molecule along with another substrate in an active site
B)   binding of a molecule to one subunit of a tetramer, which promotes faster binding to each of the other three subunits
C)   the product of one enzyme in a metabolic pathway serving as the substrate for the next enzyme in the pathway
D)   binding of the end product of a metabolic pathway to the enzyme that catalyzes the first step in the pathway

Question 8

The cellular process of synthesizing large molecules from smaller ones is defined as

Accepted Answer

A)   catalysis.
B)   metabolism.
C)   anabolism.
D)   dehydration.
E)   catabolism.

Question 9

A system at chemical equilibrium

Accepted Answer

A)   consumes energy at a steady rate.
B)   releases energy at a steady rate.
C)   consumes or releases energy at a steady rate, depending on whether it is exergonic or endergonic.
D)   can do no work.

Question 10

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)

Accepted Answer

A)   competitive inhibitor of the enzyme.
B)   noncompetitive inhibitor of the enzyme.
C)   allosteric activator of the enzyme.
D)   cofactor necessary for enzyme activity.
E)   coenzyme derived from a vitamin.

Question 11

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as ________ is to ________.

Accepted Answer

A)   exergonic; spontaneous
B)   exergonic; endergonic
C)   free energy; entropy
D)   work; energy

Question 12

In most exergonic reactions, the reactants capable of interacting to form products typically must first overcome a thermodynamic barrier known as the

Accepted Answer

A)   entropy of the reaction.
B)   energy conservation of the reaction.
C)   chemical equilibrium of the reaction.
D)   activation energy of the reaction.

Question 13

Which of the following is an example of potential rather than kinetic energy?

Accepted Answer

A)   the muscle contractions of a person mowing grass
B)   water rushing over Niagara Falls
C)   light flashes emitted by a firefly
D)   a molecule of glucose

Question 14

Please use the following information to answer the question(s) below.
A series of enzymes catalyze the reactions illustrated in the following metabolic pathway: X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme.
-What is substance X?

Accepted Answer

A)   a coenzyme
B)   an allosteric inhibitor
C)   an intermediate
D)   a substrate

Question 15

Which of the following statements concerning catabolic pathways is true?

Accepted Answer

A)   They combine molecules into larger, more energy-rich molecules.
B)   They provide energy that can be used to drive cellular work.
C)   They are endergonic.
D)   They build up complex molecules such as protein from simpler compounds.

Question 16

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

Accepted Answer

A)   The energy content of an organism is constant.
B)   The organism ultimately must obtain all of the necessary energy for life from its environment.
C)   The entropy of an organism decreases with time as the organism grows in complexity.
D)   Organisms grow by converting energy into organic matter.
E)   Life does not obey the first law of thermodynamics.

Question 17

Cooperativity is a form of allosteric activation in which

Accepted Answer

A)   the product of a metabolic pathway serves as a competitive inhibitor of an early enzyme in the pathway.
B)   all of the enzymes in a metabolic pathway are contained within a single multienzyme complex.
C)   completion of one step in a metabolic pathway is required before a subsequent step can occur.
D)   binding of a substrate molecule to one active site in a multisubunit enzyme stimulates the binding of substrate molecules to the active sites of other subunits.

Question 18

A severe fever can result in death if not brought under control because

Accepted Answer

A)   it may destroy the primary structure of cellular enzymes.
B)   it may alter the tertiary structure of cellular enzymes.
C)   it may increase the rate of cellular chemical reactions.
D)   it may result in binding inappropriate substrates by cellular enzymes.

Question 19

The mechanism by which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

Accepted Answer

A)   metabolic inhibition.
B)   noncooperative inhibition.
C)   irreversible inhibition.
D)   feedback inhibition.

Question 20

Which of the following is true of enzymes?

Accepted Answer

A)   Nonprotein cofactors alter the substrate specificity of enzymes.
B)   Enzyme function is increased if the 3-D structure or conformation of an enzyme is altered.
C)   Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.
D)   Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
E)   Enzymes increase the rate of chemical reaction by providing activation energy to the substrate.

Exam 6: An Introduction to Metabolism