Biochemistry Final Practice Problems
Which citric acid cycle reaction produces FADH2? a. succinyl-CoA synthetase b. aconitase c. α-ketoglutarate dehydrogenase complex d. isocitrate dehydrogenase e. succinate dehydrogenase
. succinate dehydrogenase
How is the regulation of glucose metabolism through glycolysis and the citric acid cycle coordinated? a.High ADP levels stimulate glycolysis and the citric acid cycle. b.High NADH levels inhibit glycolysis and the citric acid cycle. c.High citrate levels inhibit glycolysis. d.In muscle, Ca2+ release (a signal of muscle contraction) stimulates both glycogen phosphorylase and enzymes of the citric acid cycle. e.All of the answers are correct.
.All of the answers are correct.
Which statement is false about Complex I? a.It consists of more than 40 different polypeptide chains. b.It has an FMN-containing flavoprotein. c.It catalyzes the transfer of a hydride from NADH and a proton from the matrix to ubiquinone (Q). d.Its activity makes the matrix more positively charged. ●
.Its activity makes the matrix more positively charged.
•Which statement is NOT true of electron transport? • a.The mobile electron carrier coenzyme A is located in the inner mitochondrial membrane b.Electrons flow from redox centers with a lower reduction potential to redox centers with a higher reduction potential c.The electron transport chain oxidizes reduced cofactors d.Cytochrome C has a higher reduction potential than FADH2 e.None of the statements is true
.The mobile electron carrier coenzyme A is located in the inner mitochondrial membrane
•The citric acid cycle is regulated at the reactions catalyzed by citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase. What do these three reactions have in common? a.They are all close to equilibrium. b.They are all strongly exergonic. c.They all reduce NAD+ to NADH. d.They all carry out substrate-level phosphorylation.
.They are all strongly exergonic.
•Which pathway is likely to be affected by a deficiency in carnitine? a. w oxidation b. b oxidation c.uptake of fatty acids from the bloodstream d.All of the answers are correct e.None of the answers is correct
.b oxidation
Cellular uptake of LDL by the LDLR results in which homeostatic mechanism? a.binding of LDL-derived cholesterol by sterol cleavage activated protein (SCAP) b.release of sterol response element binding protein 2 (SREBP2) directly to the lysosome c.upregulation of expression of genes like ABCA1 and stearoyl-CoA desaturase 1 (SCD1) d.recycling and synthesis of new LDLR proteins expressed at the plasma membrane e.upregulation of the rate-limiting enzyme of cholesterol synthesis, HMG-CoA reductase
.binding of LDL-derived cholesterol by sterol cleavage activated protein (SCAP)
What are perilipins? a.major proteins of periwinkles b.apolipoproteins of chylomicrons c.coat proteins of lipid droplets d.cytosolic lipidated proteins e.enzymes with cholesteryl esterase activity
.coat proteins of lipid droplets
The electron-transfer chain generates ATP by: a.creating a proton-motive force. b.substrate-level phosphorylation. c.activating uncoupling protein 1 (UCP1). d.pumping phosphate ions into the intermembrane space. e.adding electrons to ADP to form ATP.
.creating a proton-motive force.
The citrate synthase step of the citric acid cycle: a.is freely reversible under physiological conditions. b.is an example of a Ping-Pong enzyme mechanism. c.does not involve ATP hydrolysis. d.is considered to be both the first and last step of the cycle
.does not involve ATP hydrolysis.
Which enzyme would NOT be expected to contribute electron carriers to oxidative phosphorylation? a.alcohol dehydrogenase b.malate dehydrogenase c.succinate dehydrogenase d.glucose 6-phosphate dehydrogenase e.glyceraldehyde 3-phosphate dehydrogenase
.glucose 6-phosphate dehydrogenase
Where does β oxidation occur? a.in the cytosol b.in the mitochondrial matrix c.in the ER lumen d.on the Golgi apparatus membrane e.at the plasma membrane
.in the mitochondrial matrix
•During oxidative phosphorylation, the proton motive force that is generated by electron transport is used to: • a.create a pore in the inner mitochondrial membrane b.generate the substrates (ADP and Pi) for the ATP synthase c.induce a conformational change in the ATP synthase d.oxidize NADH to NAD+ e.reduce O2 to H2O
.induce a conformational change in the ATP synthase
Which electron carrier or prosthetic group would NOT function after site-directed mutagenesis substituted Pro for Cys in succinate dehydrogenase? a.cytochrome c b.iron-sulfur center c.flavin adenine dinucleotide d.ubiquinone e.FMN
.iron-sulfur center
Which of these dehydrogenase enzymes is NOT found in the mitochondrial matrix? a.malate dehydrogenase b.glutamate dehydrogenase c.acyl-CoA dehydrogenase d.lactate dehydrogenase
.lactate dehydrogenase
Which of these is NOT one the three primary forms in which cholesterol is exported from the liver? a.oxysterols b.bile acids c.biliary cholesterol d.cholesteryl esters
.oxysterols
•Which pair of molecules do both purine nucleotide and histidine synthesis use early in the pathways? a.phosphoribosyl pyrophosphate and ATP b.ribose 5-phosphate and ATP c.GTP and ribulose 5-phosphate d.pyridoxal phosphate and ATP e.NAD(P)H and ATP
.phosphoribosyl pyrophosphate and ATP
What enzyme catalyzes the conversion of adenine to AMP in the salvage pathway? a.adenylate kinase b.adenosine deaminase c.adenosine phosphoribosyltransferase d.ribonucleotide reductase
.ribonucleotide reductase
How many NADH molecules are generated from the complete oxidation of one glucose? a.5 b.7 c.10 d.16 e.32
10
•What is the potential ATP yield from complete oxidation of the coenzyme A derivative of stearic acid (18:0)? a.54 b.96 c.108 d.122 e.244
122
•How much carbon dioxide is produced from the complete aerobic catabolism of one molecule of linoleate via catabolic pathways? a.18 CO2 b.17 CO2 c.16 CO2 d.15 CO2 e.8 CO2
18 CO2 Linoloic acid is C18H32O2. Each carbon atom is ultimately converted to CO2.
Succinate dehydrogenase is dysfunctional in a species of garden slug. While its metabolism is compromised on a number oflevels, it can still undergo oxidative phosphorylation. What is the maximal P/O ratio for these organisms if NADH is used as an electron source? a.1 b.1.5 c.2 d.2.5 e.4
2.5
How many electrons would enter Complex I from complete oxidation of myristic acid, 14:0? a.18 b.40 c.42 d.52 e.54
54 Note: Myristic acid undergoes 6 rounds of β oxidation, producing 7 acetyl-CoA and 6 NADH (1 NADH per round). Each acetyl-CoA yields 3 NADH in the citric acid cycle. 6 NADH + (7 acetyl-CoA×3 NADH/acetyl-CoA) = 27 NADH Each NADH molecule donates 2 electrons to Complex I. 27 NADH×2e−/NADH = 54e−
•How many reducing equivalents are transferred to electron carriers after one turn of the citric acid cycle? a.4 b.6 c.8 d.10 e.16
8
•If the fatty acid 14:1(D7) is completely catabolized to CO2 and H2O, what would be the net yield of ATP? a.90.5 ATP b.92 ATP c.92.5 ATP d.94 ATP e.94.5 ATP
90.5 ATP : Myristic acid (14:0) would afford 92 ATP (=70+15+7). However, myristoleic acid (14:1) affords only 90.5 ATP because one less FADH2 is formed
The citric acid cycle is regulated in a manner similar to glycolysis. Which molecule is an allosteric activator of BOTH of those pathways? a.ATP b.NAD+ c.ADP d.citrate e.NADH
ADP
The pyruvate dehydrogenase (PDH) complex is NOT regulated by: ● a.ADP. b.fatty acids. c.covalent modification. d.acetyl-CoA.
ADP
Which molecule is part of an important mass-action ratio in most cells and is a modulator of the three major ATP-producing pathways? a.ADP b.NAD+ c.AMP d.acetate e.NADH
ADP
•Which compound is NOT required for the oxidative decarboxylation of pyruvate to form acetyl-CoA? a.ATP. b.CoA-SH. c.FAD. d.lipoic acid. e.NAD+.
ATP
Which statement about familial hypercholesterolemia (FH) is false? a.Affected individuals have a mutation in the LDL receptor. b.Affected individuals have very high blood levels of LDL and of the cholesterol it carries. c.Affected individuals are at much greater risk of developing atherosclerosis. d.Affected individuals accumulate cholesterol in lysosomes of liver, brain, and lung.
Affected individuals accumulate cholesterol in lysosomes of liver, brain, and lung.
What is the advantage to having an enzyme complex, as in pyruvate dehydrogenase (PDH) complex? a.Multiple steps can be regulated at one point. b.Products do not need to diffuse to become substrates for the next enzymatic reaction. c.Products cannot be scavenged by other enzymes or pathways. d.Conservation of energy drives the reactions. All of the answers are correct
All of the answers are correct
•Which statement about liver X receptor (LXR) is true? a.LXR is a nuclear transcription factor. b.LXR is activated by binding of oxysterol. c.LXR forms a heterodimer with retinoid X receptor (RXR). d.LXR binds the LXR response element and promotes expression of the ABCA1 gene. All ofthe statements are true
All ofthe statements are true
Which statement regarding regulation of the citric acid cycle is false? a.Ca2+ is involved in citric acid cycle regulation in vertebrate muscle. b.Dysfunction of the citric acid cycle (e.g., due to mutations in enzymes of the cycle) is often associated with different types of cancer c.In addition to regulation of the PDH complex, regulation of the citric acid cycle occurs by regulation of the enzymes that catalyze the strongly exergonic steps. d.As [NADH]/[NAD+] increases, flux through the cycle increases.
As [NADH]/[NAD+] increases, flux through the cycle increases.
Which complex does NOT transport H+ from the mitochondrial matrix to the intermembrane space? a.Complex I b.Complex II c.Complex III d.Complex IV
Complex II
Why is the net production of ATP from palmitate (16:0) oxidation 106 ATP and not 108 ATP? a.Conversion of palmitate to palmitoyl-CoA consumes the equivalent of 2 ATP. b.The overall reaction for conversion of palmitoyl‐CoA to 16 CO2has 106 ATP on the products side of the reaction. c.Each NADH produces about 2.5 ATP, and each FADH2 produces about 1.5 ATP. d.The production of H+ by β oxidation inside a mitochondrion results in the loss of 2 ATP.
Conversion of palmitate to palmitoyl-CoA consumes the equivalent of 2 ATP.
Pyruvate is produced in glycolysis and used by the citric acid cycle in the mitochondrial matrix. How does pyruvate get into the matrix? a.It moves through the membrane by simple diffusion. b.Diffusion is facilitated through a specific uniport. c.It transforms into acetate, which moves through a facilitated transporter. d.A transporter is not needed because pyruvate from glycolysis is already in the matrix. It moves through the malate shuttle system
Diffusion is facilitated through a specific uniport
Which sequence of electron carriers transfers electrons from a fatty acyl-CoA to the mitochondrial respiratory chain? a.ETF → ubiquinone → ETF:ubiquinone oxidoreductase → FADH2 b.FADH2 → ETF → ETF:ubiquinone oxidoreductase → ubiquinone c.ETF → FADH2 → ETF:ubiquinone oxidoreductase → ubiquinone d.FADH2 → ETF:ubiquinone oxidoreductase → ubiquinone → ETF
FADH2 → ETF → ETF:ubiquinone oxidoreductase → ubiquinone
Which compound is NOT a neurotransmitter derived from tyrosine? a.dopamine b.GABA c.norepinephrine d.epinephrine
GABA
Which enzyme in the de novo purine nucleotide biosynthesis pathway produces the first intermediate with a complete purine ring? a.glutamine-PRPP amidotransferase b.AIR carboxylase c.SAICAR synthetase IMP synthase
IMP Synthase
What does apolipoprotein C-II do? a.It activates LCAT on HDL. b.It is a structural component of LDL. c.It is a ligand for the LDL receptor. d.It activates lipoprotein lipase activity on chylomicrons. e.It inhibits lipoprotein lipase activity on chylomicrons.
It activates lipoprotein lipase activity on chylomicrons.
Which statement regarding isocitrate dehydrogenase is false? a.It has a Mn2+ cofactor. b.In eukaryotes, there is an NAD+-dependent form in mitochondria and an NAD+-independent form found in both mitochondria and the cytosol. c.It catalyzes a reversible reaction under physiological conditions. d.It catalyzes an oxidative decarboxylation.
It catalyzes a reversible reaction under physiological conditions.
Which statement is false about Complex III? a.It holds ubiquinone on the matrix side of the inner mitochondrial membrane throughout the redox process. b.Its functional unit consists of two dimers made up of cytochrome b, cytochrome c1, and the Rieske iron-sulfur protein. c.It couples the oxidation of two molecules of reduced ubiquinone (QH2) with the reduction of two molecules of cytochrome c. d.It catalyzes the net movement of two protons from the N side to the P side of the inner mitochondrial membrane.
It holds ubiquinone on the matrix side of the inner mitochondrial membrane throughout the redox process.
The overall reaction to convert palmitoyl-CoA to eight acetyl-CoA: a.It consumes 8 H2O. b.It produces either 7 NADH or 7 FADH2, depending on the organelle. c.It requires 8 rounds of β oxidation. It produces 7 NADH and 7 FADH2
It produces 7 NADH and 7 FADH2
Which statement regarding the proton-motive force is false? a.It is a result of electron flow through the respiratory chain. b.It is used by ATP synthase to synthesize ATP. c.It results from an [H+] gradient across the outer mitochondrial membrane. d.It is both chemical and electrical potential energy.
It results from an [H+] gradient across the outer mitochondrial membrane.
The β oxidation of polyunsaturated fatty acids: a.It uses the same enzymes as β oxidation of saturated fatty acids, with the addition of an isomerase and a reductase. b.It requires an entirely different pathway than that used for saturated fatty acids. c.It requires propionyl-CoA carboxylase. It occursin the cytosol in vertebrates
It uses the same enzymes as β oxidation of saturated fatty acids, with the addition of an isomerase and a reductase.
Which statement regarding the citric acid cycle is false? a.Part of the chemical logic behind it involves the conversion of the relatively unreactive methyl group of acetyl-CoA to a more reactive methylene group. b.The carbon atoms that feed into the cycle as acetyl-CoA do not leave as CO2 during their first turn in the cycle. c.It is found in the mitochondria of eukaryotes. Its role is strictly limited to energy conservation during the catabolism of the acetyl group
Its role is strictly limited to energy conservation during the catabolism of the acetyl group
Why is the formation of mevalonate considered the committed step, and rate-limiting step, in cholesterol synthesis? a.Mevalonate has high phosphoryl transfer potential. b.Mevalonate is highly reactive and unstable. c.Mevalonate's formation requires three phosphoryl transfer reactions. d.Mevalonate is normally low in concentration in cells, making the reverse reaction highly unlikely. e.Mevalonate's formation requires 2 NADPH, and the next three steps each require ATP. ●
Mevalonate's formation requires 2 NADPH, and the next three steps each require ATP.
•In b oxidation, which cofactor is required for the conversion of a b-hydroxyacyl-CoA to a b-keto-acyl-CoA? a.NAD+ b.FAD c.H2O d.CoA-SH e.All of the answers are correct.
NAD+
Which statement is true regarding the reactions of ketone body metabolism? a.The enzymes that catalyze biosynthesis of ketone bodies are found in the cytosol of hepatocytes. b.NADH is produced by catabolism of D-β-hydroxybutyrate. c.Conversion of 2 acetyl-CoA to acetoacetyl-CoA is accompanied by hydrolysis of ATP to AMP and PPi. d.The liver lacks thiolase and therefore cannot use ketone bodies as fuel.
NADH is produced by catabolism of D-β-hydroxybutyrate.
•What is the reducing equivalent necessary for fatty acid synthesis? a.NADH b.FADH2 c.NADPH d.succinate e.None of the answers is correct.
NADPH
•Which additional reactant is required for oxidation of polyunsaturated fatty acids compared with saturated fatty acids? a.biotin b.O2 c.NADPH d.ATP e.FAD
NADPH
Which statement regarding synthesis of deoxyribonucleotides is false? a.They are synthesized (with the exception of dTTP) from ribonucleotides by a mechanism involving a tyrosyl radical. b.dUDP is synthesized from UDP. c.Regulation of the process occurs by binding of effectors to a primary regulation site, as well as to a site that alters the substrate specificity. Purines are acted on by purine ribonucleotide reductase, and pyrimidines are acted on by both purine and pyrimidine ribonucleotide reductases
Purines are acted on by purine ribonucleotide reductase, and pyrimidines are acted on by both purine and pyrimidine ribonucleotide reductases
Why are reactive oxygen species (ROS) generated? a.Molecular oxygen recombines with hydrogen to produce dihydrogen oxide. b.Stray electrons bind to oxygen, creating a free radical oxygen species. c.There are high ADP levels. d.There is a high NAD+/NADH ratio. e.Transfer of a H+ across the inner mitochondrial membrane is uncoupled from ATP synthase.
Stray electrons bind to oxygen, creating a free radical oxygen species.
Which statement regarding the citric acid cycle is false? a.The PDH complex is considered to be an enzyme of the citric acid cycle. b.Succinate dehydrogenase is an integral membrane protein. c.For the complete conversion of glucose to CO2,approximately 32 ATP can be synthesized. d.Succinyl-CoA synthetase and succinic thiokinase are two names for the same enzyme.
The PDH complex is considered to be an enzyme of the citric acid cycle
Which statement is false about the cytochrome electron carriers? a.Cytochromes a, b, and c are distinguished by differences in their light-absorption spectra. b.Soluble cytochrome c associates with the outer surface of the inner membrane through electrostatic interactions. c.The heme of cytochrome c is tightly, but not covalently, bound to its associated protein. Cytochromesaandbare integral proteins of the inner mitochondrial membrane
The heme of cytochrome c is tightly, but not covalently, bound to its associated protein.
•Using currently accepted P/O ratios, what is the total ATP potential yield from one acetyl-CoA in the citric acid cycle? a.8 b.10 c.24 d.32 e.106
The oxidation of one acetyl-CoA in the citric acid cycle yields three NADH (3×2.5 = 7.5) , one FADH2 (1×1.5), and one GTP/ATP. Therefore: 10
Malonyl-CoA decarboxylase inhibition is an important treatment for ischemic tissues (as in heart attacks). Why? a.The process of β oxidation requires O2 to generate energy, so preventing degradation of malonyl-CoA allows inhibition of fatty acid import into mitochondria. b.Malonyl-CoA decarboxylase generates acetyl-CoA for fatty acid synthesis, which would be inopportune during tissue ischemia. c.Glycolysis should be inhibited during ischemia, and malonyl-CoA activates glycolysis. d.All of the answers are correct. e.None of the answers is correct. ●
The process of β oxidation requires O2 to generate energy, so preventing degradation of malonyl-CoA allows inhibition of fatty acid import into mitochondria.
•Which statement is false regarding the processing of dietary lipids in vertebrates? a.Dietary lipids are emulsified by bile salts in the intestine. b.Triacylglycerols in mixed micelles in the intestine diffuse into cells of the intestinal mucosa. c.Ultimately, dietary lipids are oxidized as fuel by muscle or stored as triacylglycerols in adipose tissue. d.Dietary lipids are packaged in lipoprotein aggregates known as chylomicrons, which are then exported to the lymph system. ●
Triacylglycerols in mixed micelles in the intestine diffuse into cells of the intestinal mucosa.
Which statement regarding mutations in mitochondrial DNA is false? a.Type 1 diabetes is due to dysfunctional β-cell mitochondria resulting from mutations in the mitochondrial tRNA genes. b.Impaired ATP production due to mutations in mitochondrial genes can result in human diseases. c.Mutations in mitochondrial genes accumulate through the life of an organism. d.An individual cell may have mitochondria that are not genetically identical to each other.
Type 1 diabetes is due to dysfunctional β-cell mitochondria resulting from mutations in the mitochondrial tRNA genes.
Cholesterol is NOT converted to: a.bile acids. b.steroid hormones. c.cholesteryl ester. vitamin A
Vitamin A
•The conversion of palmitoyl-CoA (16:0) to myristoyl-CoA (14:0) and 1 mol of acetyl-CoA by the b-oxidation pathway results in the net formation of: a.1 FADH2 and 1 NADH b.1 FADH2 and 1 NADPH c.1 FADH2, 1 NADH, and 1 ATP d.2 FADH2 and 2 NADH e.2 FADH2, 2 NADH, and 1 ATP
a.1 FADH2 and 1 NADH
Which vitamin is a coenzyme to the pyruvate dehydrogenase (PDH) complex? a.pantothenate b.thiamine pyrophosphate c.niacin d.riboflavin e.All of the answers are correct.
a.All of the answers are correct.
Which statement is false about fat oxidation in hibernating bears? a.The energy of fat oxidation allows bears to maintain a body temperature close to normal. b.Amino groups released during fat oxidation can be used to make amino acids. c.Fat oxidation releases water, which replenishes water lost in breathing. d.Degradation of triacylglycerols provides a substrate for gluconeogenesis.
a.Amino groups released during fat oxidation can be used to make amino acids.
Which statement regarding regulation of acetyl-CoA carboxylase is false? a.Phosphorylation activates acetyl-CoA carboxylase. b.Acetyl-CoA carboxylase catalyzes the rate-limiting step of fatty acid biosynthesis. c.Citrate allosterically activates acetyl-CoA carboxylase. d.Active acetyl-CoA carboxylase polymerizes into long filaments.
a.Phosphorylation activates acetyl-CoA carboxylase.
•Which statement regarding the energetics of the citric acid cycle is true? a.The cycle in animal cells directly produces one ATP instead of one GTP. b.All of the energy-producing capacity of the cycle occurs in the first four reactions; the remaining reactions serve to regenerate oxaloacetate. c.Production of FADH2 by the citric acid cycle represents the energic capacity to synthesize about 1.5 ATP. d.Production of 3 NADH by the citric acid cycle represents the energic capacity to synthesize about 2.5 ATP.
a.Production of FADH2 by the citric acid cycle represents the energic capacity to synthesize about 1.5 ATP.
Which statement regarding peroxisomal β oxidation is false? a.Peroxisomal β oxidation occurs in the liver of mammals. b.The acetyl-CoA produced is largely consumed by the peroxisomal citric acid cycle. c.It produces hydrogen peroxide. The reactions aresimilar tothose of mitochondrialβoxidation
a.The acetyl-CoA produced is largely consumed by the peroxisomal citric acid cycle.
Which statement regarding ATP synthase is false? a.The γ subunit is stationary as the αβ dimers rotate around it. b.Protons flow through the a and c subunits. c.When the F1 domain is isolated, it functions as an ATPase. It is considered to haveanFodomain and an F1domain
a.The γ subunit is stationary as the αβ dimers rotate around it.
In hypoxic cells: a.a subunit of Complex IV is replaced with another subunit optimized for activity under hypoxic conditions. b.PDH activity increases. c.flux through glycolysis decreases. levels of reactive oxygen species decline
a.a subunit of Complex IV is replaced with another subunit optimized for activity under hypoxic conditions.
Which molecule is produced in high concentration as a result of both enhanced gluconeogenesis during starvation and in untreated diabetes, which has the same fate under those two conditions? a.acetyl-CoA b.glyceraldehyde 3-phosphate c.succinate d.NADH e.FADH2
a.acetyl-CoA
Which disease linked to human purine catabolism is sometimes treated with a bone marrow transplant? a.adenosine deaminase deficiency b.Lesch-Nyhan syndrome c.gout d.all of the answers are correct.
a.adenosine deaminase deficiency
•Which compound is NOT a direct source of electrons for the respiratory chain? a.cytosolic NADH b.dihydroorotate dehydrogenase c.glycerol 3-phosphate dehydrogenase d.FADH2
a.cytosolic NADH
•What two chemical mechanisms change pyruvate to acetyl-CoA in the pyruvate dehydrogenasecomplex? a.dehydrogenation and oxidation b.decarboxylation and condensation c.condensation and dehydrogenation d.dehydrogenation and decarboxylation e.condensation and oxidation
a.dehydrogenation and decarboxylation
Linoleate is an essential fatty acid in humans because humans cannot: a.desaturate a fatty acid beyond Δ9. b.synthesize a fatty acid longer than 16 carbons. c.desaturate a fatty acid more than once. d.convert stearate to oleate.
a.desaturate a fatty acid beyond Δ9.
What is the cellular location for fatty acid elongation and desaturation in both plant and animal cells? a.endoplasmic reticulum b.cytosol c.mitochondria d.peroxisomes e.glyoxisomes
a.endoplasmic reticulum
Which molecule can be produced rapidly from glycerol in only three steps, allowing an interaction between carbohydrate and lipid metabolism? a.acetyl-CoA b.glucose c.pyruvate d.glyceraldehyde 3-phosphate e.phosphoenolpyruvate
a.glyceraldehyde 3-phosphate
With each rotation of 120°, the γ subunit of FoF1 comes into contact with a different β subunit, forcing that β subunit: a.into the β-empty conformation. b.into the β-ADP conformation. c.into the β-ATP conformation. d.to catalyze the synthesis of ATP.
a.into the β-empty conformation.
For nitrogen to be in a biologically useful form: a.involves incorporation of NH4+ into glutamate and glutamine, followed by donation of nitrogen-containing groups from those amino acids into other biomolecules. b.begins by incorporation of NH4+ into α-ketoglutarate by a transamination reaction. c.occurs in bacteria and plants, primarily by the combined actions of glutamine synthetase and glutamate synthetase, resulting in incorporation of NO3- into α-ketoglutarate. d.occurs by reaction of NO3- and α-ketoglutarate to form glutamate, catalyzed by glutamate dehydrogenase. ●
a.involves incorporation of NH4+ into glutamate and glutamine, followed by donation of nitrogen-containing groups from those amino acids into other biomolecules.
•Which compound can be synthesized by plants but not by humans? a.linoleate [18:2(D9,12)]. b.palmitate (16:0). c.phosphatidylcholine. d.pyruvate. e.stearate (18:0).
a.linoleate [18:2(D9,12)].
Bacteria deep in a corn field fix nitrogen early in the spring. Once the farmer begins plowing the soil, which process would continue while the others slow or stop? a.nitrification b.denitrification c.fermentation d.nitrogen fixation e.All of these processes would slow or stop.
a.nitrification
The regulation of β oxidation: a.is not glucagon dependent in any cells in humans. b.is not directly linked to intermediates in fatty acid biosynthesis. c.occurs both by transcriptional regulation as well as by regulating transport of fatty acids into mitochondria. does not involve direct regulation of any of the four enzymes ofβoxidation
a.occurs both by transcriptional regulation as well as by regulating transport of fatty acids into mitochondria.
•Purine nucleotide and histidine synthesis both use which pair of molecules early in the pathways? a.phosphoribosyl pyrophosphate and ATP b.ribose 5-phosphate and ATP c.GTP and ribulose 5-phosphate d.pyridoxal phosphate and ATP e.NAD(P)H and ATP
a.phosphoribosyl pyrophosphate and ATP
Histidine biosynthesis in bacteria and plants: a.requires incorporation of two atoms donated by the adenine base of ATP. b.involves conversion of histamine to histidine by histamine deaminase. c.involves formation of the imidazole, followed by its transfer to alanine. requires glutamine but not glutamate as a nitrogen donor
a.requires incorporation of two atoms donated by the adenine base of ATP.
An important theme in Biochemistry is interaction among metabolic pathways. Which pathway would obviously be MOST affected by increased β oxidation of fatty acids? a.glycolysis b.the citric acid cycle c.the glyoxylate pathway d.the pentose phosphate pathway e.gluconeogenesis
a.the citric acid cycle
•The conversion of inosinate to adenylate requires Asp, a nucleoside triphosphate, and it produces fumarate. What other pathway has this same strategy? a.Cys synthesis b.Glu synthesis from Gln c.pentose phosphate, nonoxidative d.the urea cycle e.the Calvin cycle, third stage
a.the urea cycle
Which reaction mechanism has sufficient total energy yield to add coenzyme A to fatty acids but requires two enzymes? a.phosphorylation b.oxidative decarboxylation c.dehydrogenation d.substrate-level phosphorylation e.adenylylation
adenylylation
•The reactions of mitochondrial β oxidation do NOT include: a.a hydratase b.a thiolase c.a dehydrogenase d.an oxidase
an oxidase
•Which statement about triacylglycerol synthesis is correct? a.Humans can store more energy in glycogen than in triacylglycerols. b.Insulin stimulates conversion of dietary carbohydrate into triacylglycerols. c.It is not a hormone-sensitive process. d.Mammals are unable to convert carbohydrates into triacylglycerols. Phosphatidateis not on the pathway of triacylglycerol synthesis
b.Insulin stimulates conversion of dietary carbohydrate into triacylglycerols.
The equation for palmitate synthesis by fatty acid synthase is: Acetyl-CoA + 7 malonyl-CoA + 14 NADPH + 14 H+ ® palmitate + 7 CO2 + 8 CoA + 14 NADP+ + 6 H2O Why are only six waters produced by palmitate synthesis, not seven? a.One water is used to form the initial acetyl-CoA. b.One water is used to liberate palmitate from the synthase. c.One water is permanently bound to the active synthase. d.One water is used for "charging" the synthase. e.The final translocation requires an extra water.
b.One water is used to liberate palmitate from the synthase.
The addition of oligomycin, an inhibitor of ATP synthase, to mitochondria suspended in a buffered medium blocks both ATP synthesis and respiration. What would happen if 2,4-dinitrophenol (DNP) were also added to this suspension? a.Respiration and ATP synthesis would both resume. b.Respiration would resume without ATP synthesis. c.ATP synthesis would resume without respiration. Neither respiration nor ATP synthesis would resume
b.Respiration would resume without ATP synthesis.
Ribonucleotide reductase was altered by site-directed mutagenesis such that Met was added in place of Cys. What effect would this have on the activity of the enzyme? a.The active site would remove the correct hydroxyl group from ribose. b.The active site would be nonfunctional. c.The substrate specificity site would not function. d.There would be no effect on the activity of the enzyme. The enzyme would produce incorrect deoxyribonucleotides due to a lack of regulation
b.The active site would be nonfunctional.
•What is unusual about the structure of glutathione, a tripeptide of glutamate-cysteine-glycine? a.It is a common biological reducing agent. b.The cysteine forms disulfide bonds in the oxidized state. c.The glycine is methylated. d.The glutamate is connected by its g-carboxyl group. e.The sulfhydryl group (reduced form) removes toxic peroxides.
b.The cysteine forms disulfide bonds in the oxidized state.
•Which statement does NOT describe a feature of the eicosanoids? a.They are ultimately derived from dietary linoleate. b.The thromboxanes are all made from α-linolenate, and the leukotrienes are all made from arachidonate. c.PGH2 synthase (which is irreversibly inhibited by aspirin) catalyzes conversion of arachidonate to prostaglandin H2. Some eicosanoids are produced from docosahexaenoic acid
b.The thromboxanes are all made from α-linolenate, and the leukotrienes are all made from arachidonate.
Which statement does NOT describe a function associated with mitochondria? a.In brown adipocytes, electron transport is uncoupled from ATP synthesis. b.They make xenobiotic compounds more soluble for excretion. c.They release cytochrome c in the process of apoptosis. d.They are responsible for the production of steroid hormones by cytochrome P-450 enzymes.
b.They make xenobiotic compounds more soluble for excretion.
Acyl-CoA synthetase adds coenzyme A to acyl chains for the construction of certain phospholipids. Each reaction requires ATP, but AMP + Pi are products. What is the likely reaction mechanism? a.hydrolysis b.adenylylation c.carboxylation d.phosphorylation e.dehydrogenation
b.adenylylation
In cholesterol biosynthesis: a.the activated isoprene units are mevalonate and dimethyallyl pyrophosphate. b.all of the carbons originate in acetyl-CoA. c.squalene is the first fused ring structure formed. the HMG-CoA synthase is the same enzyme found in ketone body synthesis
b.all of the carbons originate in acetyl-CoA.
Which enzyme in the de novo pyrimidine biosynthesis pathway in bacteria is subject to feedback inhibition by CTP? a.carbamoyl phosphate synthetase II b.aspartate transcarbamoylase c.dihydroorotase d.dihydroorate dehydrogenase
b.aspartate transcarbamoylase
What specific lipid is a critical component of the inner mitochondrial membrane, necessary for function of the electron transfer chain? a.phosphatidylglycerol b.cardiolipin c.phosphatidylinositol d.phosphatidylserine e.phosphatidylcholine
b.cardiolipin
•Which enzyme is the major regulatory control point for b oxidation? • a.pyruvate carboxylase b.carnitine acyl transferase I c.acetyl-CoA dehydrogenase d.enoyl-CoA isomerase methylmalonyl-CoA mutase
b.carnitine acyl transferase I
•For nitrogen to be in a biologically useful form: a.denitrification must convert N2 to NH4+. b.diazotrophs must fix atmospheric nitrogen. c.annamox bacteria must convert N2 to NO2-. d.the combined actions of dinitrogenase reductase and dintrogenase must convert N2 to NO3- in an ATP-dependent process.
b.diazotrophs must fix atmospheric nitrogen.
During amino acid synthesis, the delivery of the amino group of the amino acid is usually the last step. From where is it donated? a.methionine b.glutamate c.serine d.cysteine e.aspartate
b.glutamate
Which amino acid is required to convert chorismate to anthranilate in the anthranilate synthase reaction? a.glutamate b.glutamine c.serine d.glycine
b.glutamine
Glyceroneogenesis produces: a.glycerol 3-phosphate from glycerol. b.glycerol 3-phosphate from pyruvate. c.glucose from pyruvate. triacylglycerol from glycerol and fatty acids
b.glycerol 3-phosphate from pyruvate.
•Which molecule is required as an intermediate, not a cofactor of prosthetic group, by some of the pathways for amino acid and nucleotide synthesis? a.pyridoxal phosphate b.phosphoribosyl pyrophosphate c.cyanocobalamin d.lipoate e.nicotinamide
b.phosphoribosyl pyrophosphate
The aromatic amino acids are: a.derived from acetyl-CoA. b.synthesized in bacteria in a pathway common to all three up to the production of the intermediate chorismate. c.synthesized by first making phenylalanine and then deriving tyrosine and tryptophan from phenylalanine. d.synthesized in humans by a pathway beginning with the reaction of indole with serine. ●
b.synthesized in bacteria in a pathway common to all three up to the production of the intermediate chorismate.
What is the primary allosteric inhibitor of amino acid synthesis pathways? a.ADP b.the end product amino acid c.citrate d.NH4+ e.ATP
b.the end product amino acid
•Which list CORRECTLY ranks the polarity, from most polar to least polar, for the listed substances? a.cholesteryl-ester > bile salts > cholesterol. b.cholesterol > bile salts > cholesteryl-esters. c.bile salts > cholesteryl-esters > cholesterol. d.cholesteryl-esters > cholesterol > bile salts. bile salts > cholesterol > cholesteryl-esters
bile salts > cholesterol > cholesteryl-esters
What is the final product of FAS I systems? a.12:0 b.14:0 c.16:0 d.18:0 e.20:0
c.16:0
•How many molecules of water are produced by the electron-transport chain during the complete aerobic oxidation of one molecule of pyruvate? a.3 H2O b.4 H2O c.5 H2O d.8 H2O e.10 H2O
c.5 H2O
•Phospholipids are constructed from 1,2-diacylglycerol and a polar head group using two similar strategies. What molecule provides the phosphate group for many of these phospholipids? a.ATP b.acyl phosphates c.CTP d.phosphatidic acid e.glycerol 3-phosphate
c.CTP
Which statement is true about heteroplasmic cells (and tissues) in which some of the mitochondria have a gene mutation? a.All of the cells (and tissues) will have the mutant phenotype. b.All of the cells (and tissues) will have the wild-type phenotype. c.Cells (and tissues) containing mostly wild-type mitochondria will have the wild-type phenotype. d.Cells (and tissues) containing mostly wild-type mitochondria will have the mutant phenotype.
c.Cells (and tissues) containing mostly wild-type mitochondria will have the wild-type phenotype.
Which electron-carrier complex in the respiratory chain oxidizes ubiquinone? a.Complex I b.Complex II c.Complex III d.Complex IV
c.Complex III
•Cytochrome P-450 gets its name from what characteristic? a.It is a protein that is 450 amino acids long. b.It fluoresces at 450 nm. c.It absorbs light at 450 nm. d.It has a reduction potential of -450 mV. e.It contains a 450 Dalton prosthetic.
c.It absorbs light at 450 nm
Which statement regarding heme is false? a.Glycine is a major precursor for heme biosynthesis. b.Heme is degraded to compounds that are excreted in feces and urine. c.The nonenzymatic insertion of the iron atom into protoporphyrin is a result of the high binding affinity of protoporphyrin for iron atoms. d.Heme degradation results in production of CO.
c.The nonenzymatic insertion of the iron atom into protoporphyrin is a result of the high binding affinity of protoporphyrin for iron atoms.
•Which enzymes are required to form GTP from ATP? a.adenylate kinase and a nucleoside monophosphate kinase b.adenylate kinase and nucleoside diphosphate kinase c.a nucleoside monophosphate kinase and nucleoside diphosphate kinase d.adenylate kinase, a nucleoside monophosphate kinase, and nucleoside diphosphate kinase
c.a nucleoside monophosphate kinase and nucleoside diphosphate kinase
How do biological systems overcome the high activation barrier of nitrogen fixation? a.by increasing the temperature of the system b.by increasing the partial pressure of N2 c.by binding and hydrolyzing ATP d.by oxidizing NADH to NAD+
c.by binding and hydrolyzing ATP
In the exogenous lipid transport pathway: a.HDL transports cholesterol from intestine to liver. b.VLDL transports lipids from liver to tissues. c.chylomicrons transport lipids from intestine to tissues. d.LDL is taken up by macrophages.
c.chylomicrons transport lipids from intestine to tissues.
Identify the four-step sequence that facilitates fatty acid synthesis. a.carboxylation, oxidation, hydration, oxidation b.condensation, oxidation, dehydration, oxidation c.condensation, reduction, dehydration, reduction d.carboxylation, reduction, hydration, reduction
c.condensation, reduction, dehydration, reduction
Which factor is NOT associated with regulation of glutamine synthetase? a.cumulative feedback regulation b.allosteric inhibition by histidine c.covalent activation by adenylylation d.allosteric inhibition by CTP
c.covalent activation by adenylylation
The human mitochondrial genome: a.is less susceptible to DNA damage than is nuclear DNA. b.is a linear chromosome of 16,569 base pairs. c.encodes 37 genes, 13 of which code for polypeptide chains. d.is inherited in two copies per mitochondrion, one of paternal lineage and the other of maternal lineage.
c.encodes 37 genes, 13 of which code for polypeptide chains.
Which B vitamin is required to synthesize thymidylate (dTMP) from uridylate (dUMP)? a.thiamine (vitamin B1) b.pyridoxine (vitamin B6) c.folic acid (vitamin B9) d.cobalamin (vitamin B12)
c.folic acid (vitamin B9)
Mitochondria produce a lot of acetate due to fatty acid oxidation and other pathways. Acetate is required for fatty acid synthesis in the cytosol. What transporter does NOT function in the acetate shuttle to move both acetate and the reducing equivalents of NADH across the mitochondrial membranes? a.pyruvate b.malate-α-ketoglutarate c.glutamate-aspartate d.citrate all of these operate in the acetate shuttle
c.glutamate-aspartate
The β subunits of ATP synthase: a.have three distinct isozymes. b.are each associated with a δ subunit. c.have three distinct conformations. will act as an ATPase if protons flow through theFodomain into the mitochondrion
c.have three distinct conformations.
What gas does nitrogen fixation by the dinitrogenasecomplex produce? a.oxygen b.carbon dioxide c.hydrogen d.nitrogen e.carbon monoxide
c.hydrogen
The common general mechanism for regulation of amino acid biosynthesis: a.involves feedforward activation by accumulating precursors. b.involves covalent regulation of the first committed step of each pathway. c.involves feedback inhibition by the end product of the pathway. d.allows for little coordination between the pathways, resulting in the need for the liver to constantly monitor and adjust amino acid composition of the blood.
c.involves feedback inhibition by the end product of the pathway.
Formation of sulfide from environmental sulfates needed for Cys synthesis requires 4 NADPH in a mechanism MOST similar to: a.the pentose phosphate pathway, oxidative. b.the Calvin cycle, first stage. c.nitrogen fixation. d.the glycolate pathway. e.photosystem I, noncyclic pathway.
c.nitrogen fixation.
Regulation of cholesterol biosynthesis: a.involves transcriptional regulation but not covalent regulation. b.is sensitive to insulin but not glucagon. c.occurs in the short term primarily by regulating HMG-CoA reductase. d.involves changes in the rate of biosynthesis of critical enzymes, but not changes in the rate of proteolysis of those enzymes. ●
c.occurs in the short term primarily by regulating HMG-CoA reductase.
•Which of these is NOT a stage in the synthesis of triacylglycerols? a.reaction of two fatty acyl-CoAs with glycerol 3-phosphate to form phosphatidic acid b.removal of a phosphate to form diacylglycerol c.phosphorylation of a monoacylglycerol to form lysophosphatidic acid d.reaction with a third fatty acyl-CoA to form a triacylglycerol
c.phosphorylation of a monoacylglycerol to form lysophosphatidic acid
Which factor is NOT associated with biosynthesis of palmitate (16:0)? a.consumption of a total of 8 acetyl-CoA b.production of 14 NADP+ c.production of 8 H2O d.hydrolysis of 7 ATP
c.production of 8 H2O
The chemiosmotic model: a.is supported by the observation that, when isolated mitochondria have an artificial electrochemical gradient (higher pH in the matrix) imposed on them, electrons spontaneously flow through the respiratory chain. b.requires an intact outer mitochondrial membrane. c.requires that mitochondrial ATP synthesis and electron flow through the respiratory chain be obligately coupled. is supported by the observation that isolated mitochondria that are actively respiring cause the pH of the solution they are in to increase
c.requires that mitochondrial ATP synthesis and electron flow through the respiratory chain be obligately coupled.
•Nucleotide degradation: a.is the same pathway for all nucleotides. b.results in purine bases being converted to urea in humans. c.results in production of a citric acid cycle intermediate for thymine. d.has no known associated disease states.
c.results in production of a citric acid cycle intermediate for thymine.
Why is the malate-aspartate shuttle necessary for oxidative phosphorylation in the liver? a.to bring malate into the mitochondrial matrix b.to bring aspartate out of the mitochondrial matrix c.to bring the reducing equivalents of NADH into the mitochondrial matrix d.to convert oxaloacetate into malate e.to convert glutamate into α-ketoglutarate
c.to bring the reducing equivalents of NADH into the mitochondrial matrix
Fatty acid synthase I of mammals: a.is a single polypeptide chain in its fully functional form. b.consists of two polypeptide chains: one with three enzymatic activities, the other with four enzymatic activities. c.uses malonyl-CoA to add two-carbon units to a growing fatty acyl chain. d.is a homodimer complexed with an additional polypeptide chain known as acyl carrier protein.
c.uses malonyl-CoA to add two-carbon units to a growing fatty acyl chain
The glyoxylate cycle is remarkably similar to the citric acid cycle but differs in several important ways. Which important molecule is conserved by the glyoxylate cycle but NOT the citric acid cycle? a.acetyl-CoA b.malate c.citrate d.carbon dioxide e.NADH
carbon dioxide
Which subcellular compartment has the highest ratio of [NADPH]/[NADP+] in photosynthetic plant cells? a.mitochondria b.chloroplasts c.endoplasmic reticulum d.cytosol
chloroplasts
•Which lipoprotein is the largest and least dense? a.chylomicron b.VLDL c.LDL d.HDL
chylomicron
Which compound is NOT an electron carrier involved in the respiratory chain? a.NADH b.iron-sulfur proteins c.cytochromes d.coenzyme A
coenzyme A
Which answer choice is NOT a major source of fatty acid fuels in vertebrates? a.conversion in the liver of excess dietary amino acids to fats b.conversion in the liver of excess dietary carbohydrates to fats c.fats stored in adipocytes d.fatty acids in the diet
conversion in the liver of excess dietary amino acids to fats
A derivative of a common medication was developed, and it appears to decrease the concentration of prostaglandins while decreasing pain and fever associated with certain illnesses. What enzyme is likely inhibited by this drug? a. cyclooxygenase 1 b. thromboxane synthase c. lipoxygenase d. cyclooxygenase 2 e. β-ketoacyl-ACP synthase
d. cyclooxygenase 2
•The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _____ mol of NADH, _____ mol of FADH2, and ____ mol of ATP (or GTP) • a.2; 2; 2 b.3; 1; 1 c.3; 2; 0 d.4; 1; 1 e.4; 2; 1 ●
d.4; 1; 1
Which statement regarding uncoupling protein 1 (UCP1) is false? a.It is found in brown adipose tissue. b.It forms proton-conducting pores in the inner mitochondrial membrane. c.It provides a path for protons to return to the matrix without passing through the FoF1 complex. d.It allows for ATP generation in addition to heat formation.
d.It allows for ATP generation in addition to heat formation.
Which statement about isopentenyl pyrophosphate is false? a.It is an intermediate in cholesterol biosynthesis. b.It is the activated precursor of vitamins A, E, and K. c.It is the activated precursor of ubiquinone and plastoquinone. d.It is the activated precursor of sphingomyelin.
d.It is the activated precursor of sphingomyelin.
Which cofactor does the synthesis of serine from 3-phospho-glycerate require? a.ATP b.NAD(P)H c.folate d.NAD+
d.NAD+
Which product from oxidation of fatty acids CANNOT feed into the citric acid cycle? a.acetyl-CoA b.succinyl-CoA c.succinate d.NADP+ e.FAD
d.NADP+
What enzymatic step is considered to be the rate-limiting step of fatty acid biosynthesis? a.fatty acid synthase b.thiolase c.malonyl-CoA decarboxylase d.acetyl-CoA carboxylase e.fatty acid elongase
d.acetyl-CoA carboxylase
Glutathione: a.stimulates the production of toxic peroxides. b.is derived from cysteine and glycine. c.is a tripeptide in which the amino acid residues are linked by peptide bonds. d.acts as a redox buffer. ●
d.acts as a redox buffer.
What is the advantage of fatty acid synthase (FAS) being a complex? a.no diffusion of products/substrates between reactions, increasing efficiency b.conservation of energy c.no release of growing hydrophobic product/substrate to the aqueous environment d.all of the answers are correct. none of the answers is correct
d.all of the answers are correct
Where is the acetyl-CoA added to fatty acid synthase (FAS) incorporated into the growing fatty acid? a.at the end attached to FAS b.carbons 3 and 4 at the free end c.carbons 3 and 4 at the end attached to FAS d.at the free end e.It is not incorporated into the growing fatty acid.
d.at the free end
•What specific lipid is a critical component of the inner mitochondrial membrane, necessary for function of the electron transport chain? a.plasmalogen b.diacylglycerol c.lactosylceramide d.cardiolipin e.phosphatidylinositol
d.cardiolipin
The generation of which amino acid requires the formation of 3′-phosphoadenosine 5′-phosphosulfate (PAPS)? a.methionine b.glutamate c.serine d.cysteine e.threonine
d.cysteine
•Which enzyme would NOT be expected to contribute electron carriers to oxidative phosphorylation? a.alcohol dehydrogenase b.malate dehydrogenase c.succinate dehydrogenase d.glucose 6-phosphate dehydrogenase e.glyceraldehyde 3-phosphate dehydrogenase
d.glucose 6-phosphate dehydrogenase
Which order of electron carriers is CORRECT for both fatty acid desaturation and oxidative phosphorylation, a relatively common biochemical strategy? a.flavin, nicotinamide, heme b.pyruvate, flavin, iron c.ferridoxin, flavodoxin, cytochrome d.nicotinamide, flavin, iron e.flavin, iron-sulfur center, heme
d.nicotinamide, flavin, iron
•Which molecule is an a-keto acid? a.oxaloacetate. b.citrate. c. a-ketoglutarate. d.oxaloacetate and a-ketoglutarate. e.citrate and a-ketoglutarate.
d.oxaloacetate and a-ketoglutarate.
Which factor is NOT associated with acetyl-CoA carboxylase? a.production of malonyl-CoA b.biotin cofactor c.catalysis of an irreversible reaction d.production of oxaloacetate
d.production of oxaloacetate
Both adenylylation and uridylylation play uncharacteristic roles in the formation of Gln from Glu. What are those roles? a.transfer of phosphoryl groups, forming a key reactive intermediate b.production of additional energy from inorganic pyrophosphatase acting on PPi c.regulation of Glu and Gln transport across the mitochondrial membrane d.regulation of glutamine synthetase activity e.transfer of the required second nitrogen-containing group
d.regulation of glutamine synthetase activity
What is the major energy barrier for ATP synthase? a.binding of ADP to the enzyme b.binding of Pi to the enzyme c.formation of ATP d.release of ATP from the enzyme
d.release of ATP from the enzyme
Which factor does NOT contribute to formation of atherosclerotic plaques? a.high levels of LDL in the blood b.conversion of macrophages to foam cells c.scar tissue from damaged smooth muscle tissue d.reverse cholesterol transport
d.reverse cholesterol transport
Which factor is NOT considered to be a metabolic precursor for amino acid biosynthesis? a.3-phosphoglycerate b.pyruvate c.ribose 5-phosphate d.succinate
d.succinate
•What is the primary metabolic source of the reducing power required for fatty acid synthesis and desaturation? a.the glycerol 3-phosphate shuttle b.glycolysis c.the citric acid cycle d.the pentose phosphate pathway e.the acetate shuttle system
d.the pentose phosphate pathway
•Which two chemical mechanisms change pyruvate to acetyl-CoA in the pyruvate dehydrogenase complex? a.dehydrogenation and oxidation b.decarboxylation and condensation c.condensation and dehydrogenation d.dehydrogenation and decarboxylation e.condensation and oxidation
dehydrogenation and decarboxylation
Shuttles are used to transport reducing equivalents and molecules, which themselves have no specific transporter, through the inner mitochondrial membrane. Which molecule CANNOT move through the membrane directly? a. pyruvate b. malate c. glutamate d. α-ketoglutarate e. oxaloacetate
e. oxaloacetate
How is oxidative phosphorylation inhibited during anaerobic conditions? a.A lack of terminal electron acceptor blocks the electron-transfer chain. b.ADP levels decrease. c.A buildup of glycolytic products (pyruvic acid, lactic acid) lowers pH. d.Inhibitory protein IF1 becomes functionally dimeric under acidic conditions and binds the ATP synthase inhibiting it. e.All of the answers are correct.
e.All of the answers are correct.
•Which compound is an intermediate of the b oxidation of fatty acids? a.CH3—(CH2)20—CO—COOH b.CH3—CH2—CO—CH2—CO—OPO32- c.CH3—CH2—CO—CH2—OH d.CH3—CH2—CO—CO—S—CoA e.CH3—CO—CH2—CO—S—CoA
e.CH3—CO—CH2—CO—S—CoA
How is production of reactive oxygen species (ROS) controlled? a.through increased ADP content in the matrix b.through an increase in the NAD+/NADH ratio c.with expression of superoxide dismutase d.with expression of glutathione peroxidase e.all answers are correct. ●
e.all answers are correct.
Which compound is derived from amino acids? a.spermidine b.dopamine c.serotonin d.histamine e.all of the answers are correct.
e.all of the answers are correct.
Why does β oxidation occur in the mitochondrial matrix? a.to allow coordinated regulation with fatty acid synthesis b.to coordinate production of acetyl-CoA with the introduction into the citric acid cycle c.to compartmentalize d.because necessary oxidative enzymes are present e.all of the answers are correct.
e.all of the answers are correct.
The release of carbon dioxide from the complete oxidation of pyruvate can pose problems for cells. Which molecule can easily be formed from carbon dioxide that can serve as a one-carbon donor and double as a biological buffer? a.biotin b.acetate c.glyceraldehyde 3-phosphate d.glycine e.bicarbonate
e.bicarbonate
Which strategy is NOT common in amino acid synthesis? a.one-carbon transfer reactions b.phosphorylation followed by reduction c.aminotransferase activity late in the pathway d.unusual use of either NADH or NADPH for these anabolic pathways e.carboxylase activity early in the pathway
e.carboxylase activity early in the pathway
•Which strategy is NOT common in amino acid synthesis? a.one-carbon transfer reactions b.phosphorylation followed by reduction c.aminotransferase activity late in the pathway d.unusual use of either NADH or NADPH for these anabolic pathways e.carboxylase activity early in the pathway
e.carboxylase activity early in the pathway
Which process is NOT a fate or role of cellular diacylglycerol? a.synthesis of glycerophospholipids b.synthesis of triglycerides c.functions as a second messenger d.synthesis of phosphatidic acid e.functions as an allosteric regulator of lipid metabolism
e.functions as an allosteric regulator of lipid metabolism
•Which process is not a fate or role of cellular diacylglycerol? a.synthesis of glycerophospholipids b.synthesis of triglycerides c.function as a second messenger d.synthesis of phosphatidic acid e.functions as an allosteric regulator of lipid metabolism
e.functions as an allosteric regulator of lipid metabolism
Where is the carboxyl group added to acetyl-CoA to make malonyl-CoA incorporated into the palmitic acid by FAS? a.at the end attached to FAS b.carbons 3, 6, 9, 12 and 15 from the free end c.carbons 1, 4, 7, 10 and 13 from the free end d.at the free end e.it is not incorporated into the growing fatty acid.
e.it is not incorporated into the growing fatty acid.
•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.citrate to isocitrate. b.fumarate to malate. c.malate to oxaloacetate. d.succinate to fumarate. e.succinyl-CoA to succinate.
e.succinyl-CoA to succinate.
•During fatty acid synthesis, malonyl-CoA becomes covalently attached to acyl-carrier protein via? a.ester-bond formation to a serine. b.thioester-bond formation to a cysteine. c.amide-bond formation to a lysine. d.ether-bond formation to a serine. e.thioester-bond formation to a prosthetic group.
e.thioester-bond formation to a prosthetic group.
•Carnitine is: a.a 15-carbon fatty acid b.an essential cofactor for the citric acid cycle c.essential for intracellular transport of long fatty acids d.one of the amino acids commonly found in protein e.present only in carnivorous animals
essential for intracellular transport of long fatty acids
Starvation and uncontrolled diabetes mellitus can both result in: a.ketosis, implying that the body of a person with uncontrolled diabetes mellitus is acting metabolically as though it is starving. b.ketosis, implying that ketoacidosis is a result of uncontrolled diabetes mellitus but not starvation. c.ketosis, implying that high levels of ketone bodies in the blood must be well-tolerated. d.ketosis, though neither case is due to overproduction of ketone bodies by the liver, but rather because cells are impaired in uptake of ketone bodies.
etosis, implying that the body of a person with uncontrolled diabetes mellitus is acting metabolically as though it is starving.
Coenzyme A: a.forms thioester acyl groups. b.has lipoic acid as one of its components. c.forms esters with relatively small standard free energies of hydrolysis. d.can have pyruvate linked to it through an ester linkage.
forms thioester acyl groups.
•How many of cytochrome c need to be re-oxidized for every oxygen molecule (O2) converted to water? • a.one b.two c.three d.four e.eight
four
Which factor would stimulate movement of fatty acids to muscle and the liver when blood glucose levels fall? a.insulin b.glucagon c.an increase in protein kinase C in activity d.an increase in phospholipase C activity e.an increase in citric acid cycle activity in adipose
glucagon
From which amino acid is proline derived? a.glutamate b.histidine c.glycine d.aspartate e.It is not derived from an amino acid. It is derived from 5-phosphoribosyl-1-pyrophosphate (PRPP).
glutamate
•Of what is d-aminolevulinate an essential intermediate? a.histadine b.glutamate c.trytophan d.tyrosine e.heme
heme
Which ion, atom, or molecule constitutes one reducing equivalent? a.proton (H+) b.hydrogen atom (H+ + e−) c.hydride ion (:H−) d.NADH
hydrogen atom (H+ + e−)
Xanthine oxidase converts: a.adenosine to inosine. b.inosine to hypoxanthine. c.guanine to xanthine. hypoxanthine to uric acid
hypoxanthine to uric acid
•Targeting of nucleotide metabolism by chemotherapeutic agents: a.in some cases, works by mechanism-based enzyme inactivation. b.involves interfering with folate metabolism by fluorouracil. c.is based on inhibition of the degradation pathways, resulting in accumulation of toxic metabolites in the targeted cells. d.involves inhibiting thymidylate synthase by methotrexate. ●
in some cases, works by mechanism-based enzyme inactivation.
The power of the citric acid cycle is partly in the ability to shuttle intermediates out for the synthesis of important groups of molecules. What group of molecules is produced from citrate? a.lipids and sterols b.nucleic acids (purines) c.a number of amino acids d.glucose and a few amino acids e.porphyrin rings for various molecules such as heme
lipids and sterols
The simultaneous activation of β oxidation and fatty acid synthesis in the same cells is a futile cycle. No biological work is accomplished. Which molecule prevents this futile cycle by preventing fatty acid transport through a membrane? a.acetyl-CoA b.malonyl-CoA c.palmitoyl-CoA d.ADP e.methylmalonyl-CoA
malonyl-CoA
Which factor is NOT associated with β oxidation of fatty acids with an odd number of carbons? a.malonyl-CoA as in intermediate b.a rare example in humans of an enzyme that requires a vitamin B12-derived cofactor c.repeated cycles of β oxidation until a three-carbon fragment remains d.a citric acid cycle intermediate as the end product
malonyl-CoA as in intermediate
The second cycle of the fatty acid synthesis cycle begins with the condensation of: a.acetyl-CoA with an acetyl group bound to ACP. b.acetyl-CoA with a butyryl group bound to ACP. c.malonyl-CoA with an acetyl group bound to ACP. malonyl-CoA with a butyryl group bound to ACP
malonyl-CoA with a butyryl group bound to ACP
Metabolons are: a.multienzyme complexes that ensure efficient passage of the product of one enzyme to the next enzyme in the pathway. b.products of one metabolic pathway that act as allosteric regulators of another pathway. c.metabolic intermediates in a pathway that act as allosteric regulators of that pathway. d.individual functional units of regulation for a metabolic pathway or cycle.
multienzyme complexes that ensure efficient passage of the product of one enzyme to the next enzyme in the pathway.
•Anaplerotic reactions: • a.produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates. b.produce biotin needed by pyruvate carboxylase. c.recycle pantothenate used to make CoA. d.produce pyruvate and citrate to maintain constant levels of citric acid cycle intermediates. All of the answers are correct
produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates.
•What is the extra product resulting from the b oxidation of a saturated fatty acid with 19 carbons as compared to that of a fatty acid with 18 carbons? a.acetoacetyl-CoA b.succinyl-CoA c.acetyl-CoA d.malonyl-CoA e.propionyl-CoA
propionyl-CoA
HDL particles are the densest lipoprotein because they contain the highest fraction of: a.phospholipids. b.cholesterol. c.proteins. d.triacylglycerols.
proteins
Acetone resulting from ketone body production is: a.removed from the body by exhalation. b.used as fuel in tissues other than the liver. c.not a ketone body. d.produced by nonenzymatically and enzymatically by decarboxylation of D‐β‐hydroxybutyrate.
removed from the body by exhalation.
Anaplerotic reactions: a.are also known as cataplerotic reactions. b.are defined as those that have oxaloacetate as a product. c.never involve ATP hydrolysis. replenish all citric acid cycle intermediates
replenish all citric acid cycle intermediates
•Synthesis of purine nucleotides does NOT directly involve: a.salvage pathways. b.serine. c.aspartate. folates
serine
In adipose tissue: a.stimulation by insulin results in release of fatty acids for other tissues in the body to use as fuel. b.some triacylglycerol synthesis occurs, even during starvation. c.pyruvate is converted to glycerol, which is then used for triacylglycerol synthesis. d.glucocorticoids increase expression of PEP carboxykinase, ultimately stimulating triacylglycerol synthesis. ●
some triacylglycerol synthesis occurs, even during starvation.
The term amphibolic means: a.something that is both catabolic and anabolic. b.nothing; it is a made-up word. c.thermodynamic coupling of catabolic pathways to drive anabolic pathways. d.containing both polar and nonpolar functional groups.
something that is both catabolic and anabolic
Which enzyme does NOT catalyze an anaplerotic reaction? a.pyruvate carboxylase b.PEP carboxykinase c.succinate carboxykinase d.PEP carboxylase e.malic enzyme
succinate carboxykinase
Which enzyme of the citric acid cycle is capable of a substrate-level phosphorylation? a.citrate synthase b.aconitase c.succinate dehydrogenase d.isocitrate dehydrogenase e.succinyl-CoA synthetase
succinyl-CoA synthetase
The carefully controlled regulation of glutamine synthetase is due, in part, to at least eight allosteric inhibitors. What term BEST describes the kinetics of inhibition? a.additive b.competitive c.Michaelis-Menten d.mechanism-based e.synergistic
synergistic
Membrane sphingolipids are: a.synthesized by reacting the head group with sphingosine and then attaching a fatty acyl-CoA in an amide linkage. b.dietarily essential. c.synthesized in the cytosol. d.synthesized by first reacting palmitoyl-CoA with serine.
synthesized by first reacting palmitoyl-CoA with serine
The antidiabetic drugs rosiglitazone (Avandia) and pioglitazone (Actos) decrease: a.the rate of triacylglycerol synthesis in adipose tissue. b.the release of free fatty acid from adipose tissue into the blood. c.expression of PEP carboxykinase in adipose tissue. d.sensitivity to insulin.
the release of free fatty acid from adipose tissue into the blood.
The conversion of inosinate to adenylate requires Asp, a nucleoside triphosphate, and it produces fumarate. What other pathway has this same strategy? a.Cys synthesis b.Glu synthesis from Gln c.pentose phosphate, nonoxidative d.the urea cycle e.the Calvin cycle, third stage
the urea cycle
How many acetyl-CoA molecules does it take to synthesize one molecule of mevalonate? a.one b.two c.three d.four
three
•The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the: a.carboxyl and methylene carbons of oxaloacetate. b.carboxyl group of acetate and a carboxyl group of oxaloacetate. c.carboxyl group of acetate and the keto group of oxaloacetate. d.two carbon atoms of acetate. e.two carboxyl groups derived from oxaloacetate.
two carboxyl groups derived from oxaloacetate
•δ-Aminolevulinate is an essential intermediate in the synthesis of: a.histidine. b.glutamate. c.tryptophan. d.tyrosine. heme
tyrosine
•How do fatty acids get into the mitochondrial matrix? a.spontaneously b.via the malate shuttle c.via carnitine palmitoyl transferase d.via palmitoyl-CoA transferase e.via the citrate shuttle
via carnitine palmitoyl transferase
How do large fatty acids get into the mitochondrial matrix? a.spontaneously b.via the malate shuttle c.via carnitine palmitoyltransferase d.via palmitoyl-CoA transferase e.via the citrate shuttle
via carnitine palmitoyltransferase
Which two other enzyme complexes have an E1—E2—E3structure similar to that of the pyruvate dehydrogenase (PDH) complex? a. α-ketoglutarate dehydrogenase and branched-chain α-keto acid dehydrogenase b.α-ketoglutarate dehydrogenase and lactate dehydrogenase c.branched-chain α-keto acid dehydrogenase and lactate dehydrogenase d.pyruvate carboxylase and pyruvate decarboxylase
α-ketoglutarate dehydrogenase and branched-chain α-keto acid dehydrogenase
•Calculate the free-energy change for the creation of an electrochemical gradient by a proton pump if the pH of the matrix is 0.75 units more alkaline than that of the intermembrane space, the transmembrane difference in electrical potential is 0.20 V, and the temperature is 37 °C. a.−24 kJ/mol b.−15 kJ/mol c.15 kJ/mol d.24 kJ/mol
•Note: ∆G = 2.3RT ∆pH + ZF ∆ψ = 2.3(0.008315 kJ/mol • K)(310 K)(0.75) + (+1)(96.5 kJ/V • mol)(0.20 V) = 19.3 kJ/mol + 4.45 kJ/mol = 24 kJ/mol
Calculate the standard free-energy change for the transfer of two electrons from FADH2 through the respiratory chain to molecular oxygen (E′° for FAD/FADH2 is 0.050 V in succinate dehydrogenase and E′° for O2/H2O is 0.816 V). a.−220 kJ/mol b.−150 kJ/mol c.150 kJ/mol d.220 kJ/mol
∆E′° = E′° (electron acceptor) − E′° (electron donor) = 0.816 V − 0.050 V = 0.766 V ∆G′° = −nF ∆E′° = −2(96.5 kJ/V • mol)(0.766 V) = −150 kJ/mol -150kJ/mol
