unit 4 Flashcards
1) Anaerobic glycolysis can produce ATP at a much faster rate than aerobic oxidative phosphorylation.
Answer: TRUE
2) Which of the following types of reaction does NOT occur in glycolysis? A) Isomerization B) Nucleophilic attack C) Aldol condensation D) Oxidation E) Dehydration
Answer: C
3) The standard free energy change of the glycolytic pathway to pyruvate is -79.9 kJ/mol, while the standard free energy change associated with gluconeogenesis from pyruvate is -42.7 kJ/mol. What would the standard free energy change be for a direct reversal of the glycolytic pathway.
Answer: +79.9kJ/mol
4) Glycolysis is regulated primarily by:
A) the availability of glucose-6-phosphate.
B) three strongly endergonic, nonequilibrium reactions.
C) three strongly exergonic, nonequilibrium reactions.
D) allosteric effectors of pyruvate kinase.
E) phosphorylation of phosphofructokinase.
Answer: C
5) Which of the following statements about regulation of phosphofructokinase is FALSE?
A) AMP is an activator.
B) ADP is an activator.
C) Citrate is an inhibitor.
D) Fructose 2,6-bisphosphate is an activator.
E) ATP decreases the apparent Km for fructose-6-phosphate.
Answer: E
6) Liver pyruvate kinase is activated by dephosphorylation in response to glucagon.
Answer: FALSE
7) Hexokinase, phosphofructokinase and pyruvate kinase are each subject to ________ control.
Answer: allosteric
8) Fructose-1,6-bisphosphate is a feedforward ________ activator of liver pyruvate kinase.
Answer: allosteric
9) The oxidation of glucose to lactate has a standard free energy change of approximately -196 kJ/mol. Calculate the efficiency of energy conversion if the standard free energy change for the production of ATP from ADP and inorganic phosphate is +32.2 kJ/mol.
Answer: 33.8%
10) All of the reactions of both glycolysis and gluconeogenesis occur in the cytosol.
Answer: FALSE
11) The flux rate through the gluconeogenic pathway is directly proportional to the amount of carbohydrate in the diet.
Answer: FALSE
12) Much of the regulation of gluconeogenesis is a result of the inhibition of glycolysis.
Answer: TRUE
13) Which of the following cannot be used as a precursor for gluconeogenesis? A) Glycerol B) Pyruvate C) Lactate D) Leucine E) Alanine
Answer: D
14) Flux through the pentose phosphate pathway is controlled mainly by the NADP+/NADPH ratio in the cell.
Answer: TRUE
15) The primary gluconeogenic organ in animals is: A) skeletal muscle. B) kidney medulla. C) kidney cortex. D) liver. E) heart muscle.
Answer: D
16) ________ from muscle working anaerobically is released to blood and can be taken up by liver where it is converted to pyruvate by the enzyme lactate dehydrogenase.
Answer: Lactate
17) The Pasteur effect describes the observation that yeast-metabolizing glucose anaerobically will dramatically increase their rate of glucose utilization when provided with air.
Answer: FALSE
18) Both glycolysis and gluconeogenesis are controlled by fructose 2,6-bisphosphate in response to hormones.
Answer: TRUE
19) Pyruvate carboxylase and phosphoenolpyruvate carboxykinase catalyze reactions of gluconeogenesis that bypass the reaction of glycolysis that is catalyzed by ________.
Answer: pyruvate kinase
20) Glycogen is a major energy source for skeletal muscle contraction.
Answer: TRUE
21) Polysaccharide digestion and glycogen breakdown involve sequential cleavage from ________ ends of glucose polymers.
Answer: non-reducing
22) The major product from the action of glycogen phosphorylase and the debranching enzyme glucantransferase is ________.
Answer: glucose-1-phosphate
23) Which of the following is NOT involved in glycogen synthesis? A) UDP-glucose B) Glycogenin C) Amylo-(1,4 to 1,6)-transglycosylase D) Glycogen synthase E) Glycogen phosphorylase
Answer: E
24) Which statement about control of glycogen metabolism is INCORRECT?
A) Epinephrine signals glycogen breakdown in muscle.
B) Glucagon signals glycogen breakdown in liver.
C) Glycogen phosphorylase is activated by phosphorylation.
D) Glycogen synthase is phosphorylated at only one site.
E) Glycogen synthase is activated by dephosphorylation.
Answer: D
25) Phosphorylases and phosphatases catalyze the same reaction, the removal of a phosphate group.
Answer: FALSE
26) The pentose phosphate pathway provides ________ for reductive biosynthesis and ________ for nucleic acid biosynthesis.
Answer: NADPH, ribose-5-phosphate
1) Which of the following techniques can be used to quantify protein-protein interactions? A) Co-immunoprecipitation B) Affinity chromatography C) Chemical cross-linking D) Surface plasmon resonance E) The two-hybrid system
Answer: D
2) Oxaloacetate is replenished via the ________ in plants and bacteria.
Answer: glyoxylate pathway
3) The glyoxylate cycle in plants and bacteria can be used for net carbohydrate synthesis from fat because isocitrate lyase yields glyoxylate and ________ without the loss of two carbons as occurs in the citric acid cycle.
Answer: succinate
4) All of the enzymes of the citric acid cycle are located in the mitochondrion.
Answer: TRUE
5) Which of the following does NOT apply to the reaction catalyzed by the pyruvate dehydrogenase complex?
A) The process is highly exergonic and essentially irreversible in vivo.
B) Each intermediate in the five step reaction is able to diffuse to the next active site in a sequential manner.
C) It takes place in the mitochondrion.
D) It is an oxidative decarboxylation.
E) The product is acetyl CoenzymeA.
Answer: B
6) NAD+, coenzyme A, thiamine pyrophosphate, lipoic acid and FAD are all cofactors used in the reaction catalyzed by pyruvate dehydrogenase.
Answer: TRUE
7) The citric acid cycle is classed as a reductive pathway as it produces reduced electron carriers.
Answer: FALSE
8) The two carbon atoms that are lost as CO2 in the third and fourth steps of the citric acid cycle are the same as the two carbon atoms of acetyl CoA because of the stereochemistry of the isocitrate dehydrogenase reaction.
Answer: FALSE
9) Which of the following enzymes catalyzes a reaction of the citric acid cycle that does NOT produce reduced electron carriers? A) Malate dehydrogenase B) Succinate dehydrogenase C) α-ketoglutarate dehydrogenase D) Isocitrate dehydrogenase E) Succinyl —CoA synthetase
Answer: E
10) Arsenic poisoning acts by inhibiting the citric acid cycle at the point of both pyruvate dehydrogenase and α-ketoglutarate dehydrogenase because it makes a stable adduct with the ________ groups of the dihydrolipoamide intermediate.
Answer: sulphydryl
11) One substrate level phosphorylation occurs in the citric acid cycle in the reaction catalyzed by: A) α-ketoglutarate dehydrogenase. B) succinate dehydrogenase. C) succinyl —CoA synthetase. D) isocitrate dehydrogenase. E) citrate synthase.
Answer: C
12) Taking one mole of glucose through glycolysis and the citric acid cycle generates: A) 6C02, 8 NADH/H+, 1FADH2 and 1 ATP. B) 6C02, 8 NADH/H+, 1FADH2 and 2 ATP. C) 6C02, 10 NADH/H+, 2FADH2 and 2 ATP. D) 6C02, 10 NADH/H+, 2FADH2 and 4 ATP. E) 6C02, 8 NADH/H+, 2FADH2 and 4 ATP.
Answer: D
13) Which of the following does NOT regulate flux through the citric acid cycle?
A) Substrate availability
B) The ratio of [NAD+]/[NADH]
C) Allosteric inhibition of isocitrate dehydrogenase by ADP
D) Inhibition of α-ketoglutarate dehydrogenase by succinyl CoA
E) Ca2+ activation of isocitrate dehydrogenase
Answer: A
14) The malate dehydrogenase reaction has a strongly positive standard free energy change but it proceeds in the direction of oxaloacetate because the concentration of ________ is maintained at exceedingly low levels.
Answer: oxaloacetate
15) Transamination reactions can be used to provide intermediates for the citric acid cycle.
Answer: TRUE
16) The citric acid cycle can be considered both a ________ and anabolic pathway as it is used to oxidise acetyl CoA to carbon dioxide as well as to provide precursors for other ________ pathways.
Answer: catabolic, biosynthetic
17) Acetyl CoA is a feed forward activator of the enzyme ________ ensuring sufficient oxaloacetate for the citric acid cycle to continue.
Answer: pyruvate carboxylase
1) Electrons are transferred through the respiratory chain from reduced NADH or FADH2 to oxygen in small steps with each step in the pathway associated with a slightly more ________ reduction potential.
Answer: positive
2) Calculate the standard free energy change for the reactionFADH2 + 1/2O2 → FAD + H2O given that the standard reduction potential for the reduction of oxygen to water is +0.82 V and for the reduction of FAD to FADH2 is +0.03 V.
Answer: -152kJ/mol
3) Which of the following statements is FALSE?
A) All of the protein complexes of the mitochondrial respiratory chain are bound in the inner mitochondrial membrane.
B) Cytochrome c and coenzyme Q are both soluble electron carriers that are loosely attached to the outside of the inner mitochondrial membrane.
C) Oxygen is reduced to water at complex IV of the mitochondrial respiratory chain.
D) The citric acid cycle is linked directly to the mitochondrial respiratory chain at the site of complex II.
E) During electron transport protons are pumped across the inner mitochondrial membrane from the matrix to the intermembrane space.
Answer: B
4) Which of the following is NOT an electron acceptor in the mitochondrial respiratory chain? A) FMN B) FAD C) Fe3+ D) Cu2+ E) CoQH2
Answer: E
5) All of the cytochromes in the mitochondrial respiratory chain contain the same heme moiety as found in hemoglobin.
Answer: FALSE
6) CoQ carries electrons from NADH-Coenzyme Q reductase and succinate dehydrogenase as well as other flavoproteins to CoQ:Cytochrome c oxidoreductase.
Answer: TRUE
7) Which of the following statements about oxidative phosphorylation by ATP synthase is FALSE?
A) The electrochemical gradient across the inner mitochondrial membrane generated by electron flow is used to synthesize ATP.
B) Uncouplers dissipate the electrochemical gradient but electron transport continues without ATP production.
C) Inhibitors disrupt electron flow as well as ATP synthesis.
D) A proton gradient alone without a corresponding energy input is not sufficient to drive the synthesis of ATP.
E) ATP synthesis occurs via simultaneous conformational changes in protein subunits containing catalytic sites.
Answer: D
8) Electron transport through NADH-Coenzyme Q reductase (Complex I) is accompanied by transfer of ________ protons from the matrix to the intermembrane space.
Answer: four
9) The Q cycle is responsible for transferring electrons from a two-electron donor ________ to a one-electron acceptor ________ at the point of complex III of the mitochondrial respiratory chain.
Answer: CoQH2, cytochrome c
10) Calculate the free energy change associated with transporting one proton from the matrix to the intermembrane space at 37∘C where the electrical potential across the membrane is ~ = 170 mV and the △pH is +0.75.
Answer: +20.85kJ/mol
11) Proton-driven rotation of the c-ring of the F0 unit of the F1F0 ATP synthase is required for complete passage of protons from the intermembrane space to the matrix.
Answer: TRUE
12) Oligomycin is an inhibitor of ADP phosphorylation because it blocks the flow of protons through the ________.
Answer: Fo proton channel
13) Which of the following is NOT true of respiratory control?
A) Oxidative phosphorylation is absolutely dependent on the continued flow of electrons from substrates to oxygen.
B) Oxidative phosphorylation is regulated by allosteric mechanisms.
C) The stimulation of respiration by addition of ADP is stoichiometric.
D) The rate of respiration is controlled by the balance between the △G’s for phosphorylation of ADP, electron transport and proton pumping.
E) Maintenance of respiratory control depends on the structural integrity of the mitochondrial inner membrane.
Answer: B
14) Energy derived from oxidation of acetyl-CoA in the citric acid cycle is used for the production of ________ in brown adipose tissue because the mitochondria are rich in UCP1.
Answer: heat
15) In animal cells the mitochondrial electron transport chain is responsible for reoxidizing most of the NADH produced by oxidative pathways regardless of the cellular compartment in which it was produced.
Answer: TRUE
6) The ATP yield from NADH transported across the mitochondrial inner membrane by the glycerol phosphate shuttle is the same as if the malate/aspartate shuttle were used.
Answer: FALSE
17) Calculate the efficiency of energy conversion from glucose under aerobic conditions assuming that 32 moles of ATP are produced for each mole of glucose and given that △G0’ for glucose oxidation is -2870kJ/mol and the △G0’ for ATP hydrolysis is -32.2 kJ/mol.
Answer: 36%
18) Which of the following is NOT involved in the enzymatic inactivation of reactive oxygen species? A) Superoxide dismutase B) Catalase C) Vitamin C D) Peroxiredoxin E) Peroxidase
Answer: C
19) ________, which are potentially damaging, are generated because the interactions between one electron and two electron carriers are not 100% efficient.
Answer: Reactive oxygen species
1) The heart is a completely aerobic tissue that can make use of fatty acids, lactate, glucose and ketone bodies as fuel sources.
Answer: TRUE
2) Which of the following fuel reserves can be used by skeletal muscle? A) Protein B) Glycogen C) Creatine phosphate D) Fatty acids E) All of the above
Answer: E
3) The primary factor that controls metabolism is:
A) post-translational modification of enzymes.
B) substrate availability.
C) enzyme turnover.
D) hormone signaling.
E) compartmentalization of metabolic pathways.
Answer: B
4) Which of the following organs both uses and exports fatty acids as a fuel source? A) Resting skeletal muscle B) Liver C) Adipose tissue D) Heart muscle E) B and C
Answer: E
5) The main organ that monitors and stabilizes blood glucose is the ________.
Answer: liver
6) Which of the following statements is FALSE?
A) Glucagon increases cAMP levels in the liver in response to the fasting state.
B) Epinephrine causes mobilization of triacylglycerols from adipose tissue in response to stress.
C) Insulin decreases gluconeogenesis in the liver and increases glucose uptake and glycolysis in muscle.
D) Glycogen phosphorylase is an enzyme target of insulin but not of glucagon.
E) Phosphofructokinase-1 is an enzyme target of glucagon.
Answer: D
7) Which of the following is NOT an effect of glucagon?
A) Hydrolysis of fructose-2,6-bisphosphate
B) Inhibition of glycogenolysis
C) Inhibition of pyruvate kinase
D) Phosphorylation of hormone-sensitive lipase
E) Phosphorylation of glycogen synthase
Answer: B
8) Which of the following is an endocrine regulator that inhibits food intake? A) Ghrelin B) Adiponectin C) Leptin D) Insulin E) Both C and D
Answer: E
9) Insulin and glucagon are both synthesized by the same cell types in the pancreas.
Answer: FALSE
10) Epinephrine has a longer term effect on metabolism than does glucagon.
Answer: FALSE
11) AMPK and mTOR play opposing roles in regulating metabolic activity in response to energy status.
Answer: TRUE
12) Sirtuins are deacetylases that are ________-dependent and therefore can respond to the redox state of the cell.
Answer: NAD+
13) A side effect of diabetes is the production of acetone from the decarboxylation of acetoacetate due to ketoacidosis.
Answer: TRUE
14) One of the metabolic adaptations that occurs with prolonged starvation is the increased production of ________ because there is insufficient oxaloacetate for oxidation of all the acetyl CoA produced from fat breakdown.
Answer: ketone bodies
5) Calculate the approximate weight gain per annum if energy intake exceeds energy expenditure by 5 g (1 teaspoon) of sugar per day. Assume that 120 g sugar yields ~1760 kJ of energy and adipose tissue contains ~30 MJkg-1.
Answer: 0.89 kg
1) Which of the following is an extracellular messenger involved in signal transduction? A) Cyclic GMP B) Ca2+ C) Epinephrine D) Rhodopsin E) Diacylglycerol
Answer: C
2) Hormone action is ultimately controlled by the cells that secrete the hormone.
Answer: FALSE
3) Which of the following compounds can act as second messengers in signal transduction pathways? A) Cyclic AMP B) Phospholipase C C) Adenylate cyclase D) Phosphotidylinositol 4,5-bisphosphate E) Both A and D
Answer: A
4) G proteins are membrane-bound proteins that bind GDP when inactive.
Answer: TRUE
5) The membrane-bound receptor in G protein-coupled signal transduction is quite separate to the effector enzyme which catalyses the formation of an intracellular ________.
Answer: second messenger
6) Which of the following does NOT belong to a receptor tyrosine kinase family?
A) Platelet-derived growth factor receptor
B) Insulin receptor
C) Fibroblast growth factor receptor
D) Thyroid receptor
E) Epidermal growth factor receptor
Answer: D
7) Receptor tyrosine kinases are membrane-spanning proteins with an intrinsic tyrosine kinase domain on the extracellular side of the membrane.
Answer: FALSE
8) The end result of a signal transduction pathway is often a change in gene expression.
Answer: TRUE
9) Nuclear receptors: A) reside on the nuclear membrane. B) do not bind to hormones. C) reside only within the nucleus of a cell. D) are DNA rather than proteins. E) are transcriptional regulators.
Answer: E
10) Name the amino acid residue that is used to complex zinc ions in the zinc finger motif of steroid receptors.
Answer: cysteine
11) The drug tamoxifen can be used as an anti-cancer drug in some breast tumors as it binds to the ________ but does not activate estrogen-responsive genes.
Answer: estrogen receptor
12) Steroid hormones are cytosolic ligands for a class of nuclear receptors that exert their effects by binding to specific sites on ________.
Answer: DNA
13) The protein products of viral ________ are often components of signal transduction pathways that result in tumorigenesis.
Answer: oncogenes
14) Most synaptic transmission events are mediated electrically through gap junctions between cells.
Answer: FALSE
