Test Bank - Lehninger Principles of Biochemistry, 7th, and 8th
Edition by Nelson, All Chapters
Glycogen is converted to monosaccharide units by:
A) glucokinase.
B) glucose-6-phosphatase
C) glycogen phosphorylase.
D) glycogen synthase.
E) glycogenase. - ANSWER: C) glycogen phosphorylase.
The glycogen-branching enzyme catalyzes:
A) degradation of (α1 → 4) linkages in glycogen
B) formation of (α1 → 4) linkages in glycogen.
C) formation of (α1 → 6) linkages during glycogen synthesis.
D) glycogen degradation in tree branches.
E) removal of unneeded glucose residues at the ends of branches. - ANSWER: C) formation of (α1 → 6)
linkages during glycogen synthesis.
Glycogenin:
A) catalyzes the conversion of starch into glycogen.
B) is the enzyme responsible for forming branches in glycogen.
C) is the gene that encodes glycogen synthase.
D) is the primer on which new glycogen chains are initiated.
E) regulates the synthesis of glycogen. - ANSWER: D) is the primer on which new glycogen chains are
initiated.
Which of the following is true of glycogen synthase?
A) Activation of the enzyme involves a phosphorylation.
B) It catalyzes addition of glucose residues to the nonreducing end of a glycogen chain by formation
of (α1 → 4) bonds.
C) It uses glucose-6-phosphate as donor of glucose units
D) The conversion of an active to an inactive form of the enzyme is controlled by the concentration
of cAMP.
E) The enzyme has measurable activity only in liver. - ANSWER: B) It catalyzes addition of glucose
residues to the nonreducing end of a glycogen chain by formation
of (α1 → 4) bonds.
Which one of the following statements abour mammalian glycogen synthase is not correct?
A) It is especially predominant in liver and muscle.
B) The donor molecule is a sugar nucleotide.
C) The phosphorylated form of this enzyme is inactive.
D) This enzyme adds glucose units to the nonreducing end of glycogen branches.
E) This enzyme adds the initial glucose unit to a tyrosine residue in glycogenin. - ANSWER: E) This
enzyme adds the initial glucose unit to a tyrosine residue in glycogenin.
The enzyme glycogen phosphorylase:
A) catalyzes a cleavage of β (1 → 4) bonds.
B) catalyzes a hydrolytic cleavage of (α1 → 4) bonds.
C) is a substrate for a kinase.
, D) uses glucose 6-phosphate as a substrate.
E) uses glucose as a substrate. - ANSWER: B) catalyzes a hydrolytic cleavage of (α1 → 4) bonds.
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. - ANSWER: B) maintaining 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. - ANSWER: C) the 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 - ANSWER: A) Activation by cleavage of an
inactive zymogen
Pages: 575-576 Difficulty: 2 Ans: D
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 - ANSWER: D) 1, 3, 4
Cellular isozymes of pyruvate kinase are allosterically inhibited by:
A) high concentrations of AMP.
B) high concentrations of ATP.
C) high concentrations of citrate.
D) low concentrations of acetyl-CoA.
E) low concentrations of ATP. - ANSWER: B) high concentrations of ATP.
Edition by Nelson, All Chapters
Glycogen is converted to monosaccharide units by:
A) glucokinase.
B) glucose-6-phosphatase
C) glycogen phosphorylase.
D) glycogen synthase.
E) glycogenase. - ANSWER: C) glycogen phosphorylase.
The glycogen-branching enzyme catalyzes:
A) degradation of (α1 → 4) linkages in glycogen
B) formation of (α1 → 4) linkages in glycogen.
C) formation of (α1 → 6) linkages during glycogen synthesis.
D) glycogen degradation in tree branches.
E) removal of unneeded glucose residues at the ends of branches. - ANSWER: C) formation of (α1 → 6)
linkages during glycogen synthesis.
Glycogenin:
A) catalyzes the conversion of starch into glycogen.
B) is the enzyme responsible for forming branches in glycogen.
C) is the gene that encodes glycogen synthase.
D) is the primer on which new glycogen chains are initiated.
E) regulates the synthesis of glycogen. - ANSWER: D) is the primer on which new glycogen chains are
initiated.
Which of the following is true of glycogen synthase?
A) Activation of the enzyme involves a phosphorylation.
B) It catalyzes addition of glucose residues to the nonreducing end of a glycogen chain by formation
of (α1 → 4) bonds.
C) It uses glucose-6-phosphate as donor of glucose units
D) The conversion of an active to an inactive form of the enzyme is controlled by the concentration
of cAMP.
E) The enzyme has measurable activity only in liver. - ANSWER: B) It catalyzes addition of glucose
residues to the nonreducing end of a glycogen chain by formation
of (α1 → 4) bonds.
Which one of the following statements abour mammalian glycogen synthase is not correct?
A) It is especially predominant in liver and muscle.
B) The donor molecule is a sugar nucleotide.
C) The phosphorylated form of this enzyme is inactive.
D) This enzyme adds glucose units to the nonreducing end of glycogen branches.
E) This enzyme adds the initial glucose unit to a tyrosine residue in glycogenin. - ANSWER: E) This
enzyme adds the initial glucose unit to a tyrosine residue in glycogenin.
The enzyme glycogen phosphorylase:
A) catalyzes a cleavage of β (1 → 4) bonds.
B) catalyzes a hydrolytic cleavage of (α1 → 4) bonds.
C) is a substrate for a kinase.
, D) uses glucose 6-phosphate as a substrate.
E) uses glucose as a substrate. - ANSWER: B) catalyzes a hydrolytic cleavage of (α1 → 4) bonds.
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. - ANSWER: B) maintaining 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. - ANSWER: C) the 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 - ANSWER: A) Activation by cleavage of an
inactive zymogen
Pages: 575-576 Difficulty: 2 Ans: D
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 - ANSWER: D) 1, 3, 4
Cellular isozymes of pyruvate kinase are allosterically inhibited by:
A) high concentrations of AMP.
B) high concentrations of ATP.
C) high concentrations of citrate.
D) low concentrations of acetyl-CoA.
E) low concentrations of ATP. - ANSWER: B) high concentrations of ATP.
