Which one below is NOT a kind of high energy compound?
答案: 【 G-6-P】
Enzymes are potent catalysts because they:
A: are consumed in the reactions they catalyze.
B: are very specific and can prevent the conversion of products back to substrates.
C: increase the equilibrium constants for the reactions they catalyze.
D: lower the activation energy for the reactions they catalyze.
答案: 【 lower the activation energy for the reactions they catalyze.】
Which statement about allosteric control of enzymatic activity is FALSE?
A: Allosteric effectors give rise to sigmoidal V versus [S] kinetic plots.
B: An effector may either inhibit or activate an enzyme.
C: Binding of the effector changes the conformation of the enzyme molecule.
D: Heterotropic allosteric effectors compete with substrate for binding sites.
答案: 【 Heterotropic allosteric effectors compete with substrate for binding sites.】
A small molecule that DECREASES the activity of an enzyme by binding to a site other than the catalytic site is termed a(n):
A: allosteric inhibitor.
B: alternative inhibitor.
C: competitive inhibitor.
D: stereospecific agent.
答案: 【 allosteric inhibitor.】
Which amino acid is NOT one that may be targeted for phosphorylation to modulate the activity of an enzyme?
答案: 【 Ala】
Which type of enzyme is responsible for attaching phosphate groups to specific amino acids?
A: a protein phosphatase
B: a protein kinase
C: a protein glycosylase
D: an ATPase
答案: 【 a protein kinase】
Which reaction in glycolysis requires ATP as a substrate?
B: glyceraldehyde-3-phosphate dehydrogenase
C: pyruvate kinase
答案: 【 hexokinase】
Which reaction in glycolysis produces ATP as a product?
B: glyceraldehyde-3-phosphate dehydrogenase
C: pyruvate kinase
答案: 【 pyruvate kinase】
During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is:
A: dihydroxyacetone phosphate → glycerol 3-phosphate.
B: pyruvate → lactate.
C: isocitrate → α-ketoglutarate.
D: oxaloacetate → malate.
答案: 【 pyruvate → lactate.】
The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a net gain of:
A: 1 mol of ATP.
B: 1 mol of NADH.
C: 2 mol of ATP.
D: 2 mol of NADH.
答案: 【 2 mol of ATP.】
In comparison with the resting state, actively contracting human muscle tissue has a:
A: higher concentration of ATP.
B: higher rate of lactate formation.
C: lower consumption of glucose.
D: lower rate of consumption of oxygen
答案: 【 higher rate of lactate formation.】
Which compound CANNOT serve as the starting material for the synthesis of glucose via gluconeogenesis?
答案: 【 acetate】
An enzyme used in both glycolysis and gluconeogenesis is:
A: 3-phosphoglycerate kinase.
B: glucose 6-phosphatase.
答案: 【 3-phosphoglycerate kinase.】
Which statement about gluconeogenesis is FALSE?
A: For starting materials, it can use carbon skeletons derived from certain amino acids.
B: It consists entirely of the reactions of glycolysis, operating in the reverse direction.
C: It employs the enzyme glucose 6-phosphatase.
D: It is one of the ways that mammals maintain normal blood glucose levels
答案: 【 It consists entirely of the reactions of glycolysis, operating in the reverse direction.】
In humans, gluconeogenesis:
A: can result in the conversion of protein into blood glucose.
B: helps to reduce blood glucose after a carbohydrate-rich meal.
C: is essential in the conversion of fatty acids to glucose.
D: requires the enzyme hexokinase.
答案: 【 can result in the conversion of protein into blood glucose.】
Which statement about the pentose phosphate pathway is CORRECT?
A: It generates 36 mol of ATP per mole of glucose consumed.
B: It is a reductive pathway; it consumes NADH.
C: It is present in plants, but not in animals.
D: It provides precursors for the synthesis of nucleotides.
答案: 【 It provides precursors for the synthesis of nucleotides.】
The metabolic function of the pentose phosphate pathway is to:
A: act as a source of ADP biosynthesis.
B: generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
C: participate in oxidation-reduction reactions during the formation of H2O.
D: provide intermediates for the citric acid cycle.
答案: 【 generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.】
Which compound(s) is/are a high-energy intermediate(s) in glycolysis?
A: fructose 1,6-bisphosphate
C: 1,3-bisphosphoglycerate and phosphoenol pyruvate
D: fructose 1,6-bisphosphate, 1,3-bisphosphoglycerate, and phosphoenol pyruvate
答案: 【 1,3-bisphosphoglycerate and phosphoenol pyruvate】
Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which compound would you expect to decrease in concentration?
答案: 【 fumarate】
Which compound is NOT an intermediate of the citric acid cycle?
答案: 【 acetyl-CoA】
In mammals, what process does NOT occur during the citric acid cycle?
A: formation of α-ketoglutarate
B: generation of NADH and FADH2
C: metabolism of acetyl-CoA to carbon dioxide
D: net synthesis of oxaloacetate from acetyl-CoA
答案: 【 net synthesis of oxaloacetate from acetyl-CoA】
Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of:
A: 1 mol of citrate.
B: 1 mol of FADH2.
C: 1 mol of NADH.
D: 1 mol of oxaloacetate.
答案: 【 1 mol of FADH2.】
Which factor is NOT associated with the oxidation of substrates by the citric acid cycle?
A: CO2 production
答案: 【 NADPH】
Which enzymatic activity would be decreased by thiamine deficiency?
A: α-ketoglutarate dehydrogenase complex
B: isocitrate dehydrogenase
C: malate dehydrogenase
答案: 【 α-ketoglutarate dehydrogenase complex】
The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of:
A: succinyl-CoA to succinate.
B: citrate to isocitrate.
C: fumarate to malate.
D: succinate to fumarate.
答案: 【 succinyl-CoA to succinate.】
Which cofactor is required for the conversion of succinate to fumarate in the citric acid cycle?
答案: 【 FAD】
Which process is NOT a metabolic fate for pyruvate in liver tissue?
A: reduction to lactate
B: oxidative decarboxylation to acetyl-CoA
C: phosphorylation to phosphoenolpyruvate
D: carboxylation to oxaloacetate
答案: 【 phosphorylation to phosphoenolpyruvate】
Covalent modification is one way the activity of specific enzymes can be regulated. Which enzyme is NOT regulated in this way?
B: pyruvate dehydrogenase
C: phosphorylase kinase
D: All of these enzymes are regulated by covalent modification.
答案: 【 All of these enzymes are regulated by covalent modification.】
Which statement about 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 active.
D: This enzyme adds the initial glucose unit to a tyrosine residue in glycogenin.
答案: 【 The phosphorylated form of this enzyme is active.】
Which statement 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 enzyme has measurable activity only in liver.
答案: 【 It catalyzes addition of glucose residues to the nonreducing end of a glycogen chain by formation of (α1 -4) bonds.】
Which statement is TRUE of muscle glycogen phosphorylase?
A: It catalyzes phosphorolysis of the (α1-6) bonds at the branch points of glycogen.
B: It degrades glycogen to form glucose 6-phosphate.
C: It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP.
D: It removes glucose residues from the reducing ends of the glycogen chains.
答案: 【 It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP.】
Which statement is TRUE of glycogen synthesis and breakdown?
A: Phosphorylation activates the enzyme responsible for breakdown, and inactivates the synthetic enzyme.
B: Synthesis is catalyzed by the same enzyme that catalyzes breakdown.
C: The immediate product of glycogen breakdown is free glucose.
D: Under normal circumstances, glycogen synthesis and glycogen breakdown occur simultaneously and at high rates.
答案: 【 Phosphorylation activates the enzyme responsible for breakdown, and inactivates the synthetic enzyme.】
Glycogen phosphorylase a can be inhibited at an allosteric site by:
答案: 【 glucose.】
Starting from glucose, what is the net number of NTP molecules used in the synthesis of glycogen?