Biochemistry 1 Exam 3 Chapter 15
Multiple Choice
Aside from maintaining the integrity of its hereditary material, the most important
general metabolic concern of a cell is:
A) keeping its glucose levels high.
B) maintaining a constant supply and concentration of ATP.
C) preserving its ability to carry out oxidative phosphorylation.
D) protecting its enzymes from rapid degradation.
E) running all its major metabolic pathways at maximum efficiency. -
answersmaintaining a constant supply and concentration of ATP
If the mass action ratio, Q, for a reaction under cellular conditions is larger than the
equilibrium constant, Keq, then:
A) the reaction will be at equilibrium.
B) the reaction will go backward and be endergonic.
C) the reaction will go backward and be exergonic.
D) the reaction will go forward and be endergonic.
E) the reaction will go forward and be exergonic. - answersThe reaction will go
backward and be exergonic.
Which one of the following types of mechanisms is not known to play a role in the
reversible alteration of enzyme activity?
A) Activation by cleavage of an inactive zymogen
B) Allosteric response to a regulatory molecule
C) Alteration of the synthesis or degradation rate of an enzyme
D) Covalent modification of the enzyme
E) Interactions between catalytic and regulatory subunits - answersActivation by
cleavage of an inactive zymogen
The flux control coefficient for an enzyme in a multistep pathway depends on:
A) the concentration of the enzyme itself.
B) the concentration of other enzymes in the pathway.
C) the levels of regulatory molecules.
D) the amounts of substrate molecules present at each step.
E) all of the above. - answersAll of the above
, The elasticity coefficient for an enzyme in a multistep pathway depends on:
A) the concentration of the enzyme itself.
B) the levels of regulatory molecules.
C) the amounts of substrate molecules present at each step.
D) both A and C.
E) both B and C. - answersBoth B and C
Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the
glycolytic pathway that are highly exergonic and essentially irreversible. Reactions
carried out by which three of the enzymes listed must be bypassed in the gluconeogenic
pathway?
1) Hexokinase
2) Phosphoglycerate kinase
3) Phosphofructokinase-1
4) Pyruvate kinase
5) Triosephosphate isomerase
A) 1, 2, 3
B) 1, 2, 4
C) 1, 4, 5
D) 1, 3, 4
E) 2, 3, 4 - answers1,3,4
There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting
fructose-6-phosphate and fructose-1,6-bisphosphate. Which one of the following
statements about this regulation is not correct?
A) Fructose-2,6-bisphosphate activates phosphofructokinase-1.
B) Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase.
C) The fructose-1,6-bisphosphatase reaction is exergonic.
D) The phosphofructokinase-1 reaction is endergonic.
E) This regulation allows control of the direction of net metabolite flow through the
pathway. - answersThe phosphofructokinase-1 reaction is endergonic.
Which of the following statements is true of muscle glycogen phosphorylase?
A) It catalyzes phosphorolysis of the (alpha1 6) bonds at the branch points of glycogen.
B) It catalyzes the degradation of glycogen by hydrolysis of glycosidic bonds.
C) It degrades glycogen to form glucose 6-phosphate.
D) It exists in an active (a) form and an inactive (b) form that is allosterically regulated
by AMP.
E) It removes glucose residues from the reducing ends of the glycogen chains. -
answersIt exists in an active (a) form and an inactive (b) form that is allosterically
regulated by AMP.
Multiple Choice
Aside from maintaining the integrity of its hereditary material, the most important
general metabolic concern of a cell is:
A) keeping its glucose levels high.
B) maintaining a constant supply and concentration of ATP.
C) preserving its ability to carry out oxidative phosphorylation.
D) protecting its enzymes from rapid degradation.
E) running all its major metabolic pathways at maximum efficiency. -
answersmaintaining a constant supply and concentration of ATP
If the mass action ratio, Q, for a reaction under cellular conditions is larger than the
equilibrium constant, Keq, then:
A) the reaction will be at equilibrium.
B) the reaction will go backward and be endergonic.
C) the reaction will go backward and be exergonic.
D) the reaction will go forward and be endergonic.
E) the reaction will go forward and be exergonic. - answersThe reaction will go
backward and be exergonic.
Which one of the following types of mechanisms is not known to play a role in the
reversible alteration of enzyme activity?
A) Activation by cleavage of an inactive zymogen
B) Allosteric response to a regulatory molecule
C) Alteration of the synthesis or degradation rate of an enzyme
D) Covalent modification of the enzyme
E) Interactions between catalytic and regulatory subunits - answersActivation by
cleavage of an inactive zymogen
The flux control coefficient for an enzyme in a multistep pathway depends on:
A) the concentration of the enzyme itself.
B) the concentration of other enzymes in the pathway.
C) the levels of regulatory molecules.
D) the amounts of substrate molecules present at each step.
E) all of the above. - answersAll of the above
, The elasticity coefficient for an enzyme in a multistep pathway depends on:
A) the concentration of the enzyme itself.
B) the levels of regulatory molecules.
C) the amounts of substrate molecules present at each step.
D) both A and C.
E) both B and C. - answersBoth B and C
Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the
glycolytic pathway that are highly exergonic and essentially irreversible. Reactions
carried out by which three of the enzymes listed must be bypassed in the gluconeogenic
pathway?
1) Hexokinase
2) Phosphoglycerate kinase
3) Phosphofructokinase-1
4) Pyruvate kinase
5) Triosephosphate isomerase
A) 1, 2, 3
B) 1, 2, 4
C) 1, 4, 5
D) 1, 3, 4
E) 2, 3, 4 - answers1,3,4
There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting
fructose-6-phosphate and fructose-1,6-bisphosphate. Which one of the following
statements about this regulation is not correct?
A) Fructose-2,6-bisphosphate activates phosphofructokinase-1.
B) Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase.
C) The fructose-1,6-bisphosphatase reaction is exergonic.
D) The phosphofructokinase-1 reaction is endergonic.
E) This regulation allows control of the direction of net metabolite flow through the
pathway. - answersThe phosphofructokinase-1 reaction is endergonic.
Which of the following statements is true of muscle glycogen phosphorylase?
A) It catalyzes phosphorolysis of the (alpha1 6) bonds at the branch points of glycogen.
B) It catalyzes the degradation of glycogen by hydrolysis of glycosidic bonds.
C) It degrades glycogen to form glucose 6-phosphate.
D) It exists in an active (a) form and an inactive (b) form that is allosterically regulated
by AMP.
E) It removes glucose residues from the reducing ends of the glycogen chains. -
answersIt exists in an active (a) form and an inactive (b) form that is allosterically
regulated by AMP.
