Chapter 17
Succinate dehydrogenase
A membrane-bound enzyme of the citric acid cycle that catalyzes an oxidation reaction is ______.
Option D: Pyruvate carboxylase and pyruvate dehydrogenase You got it right
Acetyl-CoA is a regulator for which of the following enzymes? A Option A: Pyruvate carboxylase B Option B: Pyruvate dehydrogenase C Option C: -ketoglutarate dehydrogenase D Option D: Pyruvate carboxylase and pyruvate dehydrogenase E Option E: Pyruvate carboxylase, pyruvate dehydrogenase and -ketoglutarate dehydrogenase
Option A: The amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased. You got it right
An individual with a shortage of B vitamins (which include thiamine and riboflavin) may feel fatigued as a result of decreased pyruvate dehydrogenase activity. Which of the following would be TRUE regarding this shortage? A Option A: The amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased. B Option B: A decrease in the amount of NADH would likely decrease activity of citrate synthase. C Option C: Flux through the citric acid cycle would cease until adequate pyruvate is available. D Option D: none of the above E Option E: all of the above
Option C: Pyruvate carboxylase You got it right
Anapleurotic reactions are essential to the functioning of the citric acid cycle. Which of the following enzymes catalyzes such a reaction? A Option A: Glyceraldehyde-3-phosphate dehydrogenase B Option B: Citrate synthase C Option C: Pyruvate carboxylase D Option D: Malate dehydrogenase
Option C: 15 ATP You got it right
Assume that pyruvate is completely catabolized under aerobic conditions to CO2 and H2O. What is the net yield of ATP that can be expected from this? Assume that re-oxidation of NADH via the electron transport chain yields the equivalent of 3 ATP, and that re-oxidation of FADH2 yields 2 ATP. A Option A: 12 ATP B Option B: 18 ATP C Option C: 15 ATP D Option D: 10 ATP
Option B: Researchers suspect that portions of the reverse cycle may have been responsible for fixing CO2 You got it right
Bioinformatics has identified some enzymes used in the citric acid cycle in primitive bacteria. Once such a cycle utilized many of the citric acid cycle intermediates but occurred in the reverse direction. Researchers suspect which of the following based on this information? Option A: Researchers suspect that the "original" citric acid cycle was used by all species. Option B: Researchers suspect that portions of the reverse cycle may have been responsible for fixing CO2 Option C: Researchers suspect that early methods for converting pyruvate to acetyl CoA did not exist. Option D: Researchers suspect that the current "clockwise" version of the citric acid cycle could be used to help humans feed off CO2. Option E: Researchers suspect that primitive prokaryotic use of the citric acid enzymes were focused on the production of CO2 rather than the use of CO2.
Option A: acetyl-CoA You got it right
Condensation of ____ with oxaloacetate yield citrate. A Option A: acetyl-CoA B Option B: α-ketoglutarate C Option C: isocitrate D Option D: citrophosphate E Option E: oxalosuccinate
Option C: The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell. You got it right
Consider the following reaction which has a ΔG°'≈ +30 kJ/mol. malate + NAD+ → oxaloacetate + NADH + H+ In muscle cells, the reaction proceeds as written. Which of the following explains how the reaction occurs as written despite the positive value for ΔG°'? A Option A: It is thermodynamically favored under standard conditions. B Option B: In the cell, it is kinetically favored, even though it's thermodynamically unfavorable. C Option C: The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell. D Option D: [H+] must be higher in muscle than under standard conditions, thus altering ΔG° to ΔG°'. E Option E: None of the above.
Option B: 12, 14 and 15 You got it right
Consider the reactions of the citric acid cycle in the figure. At which steps are carbon atoms added to or removed from the reactants? A Option A: 12, 13 and 14 B Option B: 12, 14 and 15 C Option C: 12, 15 and 19 D Option D: 12, 14 and 19
Option B: isocitriate You got it right
Considering the reactions within the citric acid cycle, which of the following molecules will be produced from the intermediate pictured below? A Option A: citrate B Option B: isocitriate C Option C: succinate D Option D: succinyl-CoA E Option E: α-ketoglutarate
Option B: hexokinase You got it right
Covalent modification is one way the activity of specific enzymes can be regulated. Which enzyme below is not regulated in this way? A Option A: phosphofructokinase-2 B Option B: hexokinase C Option C: glycogen synthase D Option D: E1 of the pyruvate dehydrogenase complex E Option E: glycogen phosphorylase
Option C: oxalosuccinate You got it right
During the oxidation of isocitrate, _____ is decarboxylated to form α-ketoglutarate. A Option A: hydroxyethyl-TPP B Option B: carboxybiotin C Option C: oxalosuccinate D Option D: succinyl-phosphate E Option E: none of the above
Option C: lysine You got it right
E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a ______ residue on the enzyme? A Option A: tyrosine B Option B: serine C Option C: lysine D Option D: arginine E Option E: cysteine
1.5
For every FADH2 that is generated by the citric acid cycle, approximately _________ ATP are produced from ADP and Pi.
2.5
For every NADH that passes its electrons on to the electron transport chain, approximately __________ ATP are produced from ADP and Pi.
False
Gluconeogenesis takes place in the mitochondrion and oxaloacetate must be converted to malate or aspartate for transport out of the cytosol. (T/F)
Option D: At many points, including all of the above.
How is flux throughout the citric acid cycle controlled? A Option A: Primarily by control of citrate synthase. B Option B: Primarily by control of isocitrate dehydrogenase. C Option C: Primarily by control of alpha-ketoglutarate dehydrogenase. D Option D: At many points, including all of the above.
Option C: 3 You got it right
How many NADH are produced when one acetyl group is oxidized in the citric acid cycle? A Option A: 1 B Option B: 2 C Option C: 3 D Option D: 4 E Option E: more than 4
Option D: 8 You got it right
How many electrons are transferred from one acetyl group during the citric acid cycle? A Option A: 2 B Option B: 4 C Option C: 6 D Option D: 8 E Option E: 10
Option B
If acetyl-CoA labeled with 14C, as shown in the figure to the right, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle?
mitochondrion
In eukaryotes, all of the enzymes for the citric acid cycle are located in the _____________
Option B: mitochondrial matrix; cytosol You got it right
In eukaryotes, the citric acid cycle occurs in the _____ and therefore requires that reactants of the citric acid cycle be transported from the _____. A Option A: cytosol; mitochondrial matrix B Option B: mitochondrial matrix; cytosol C Option C: endoplasmic reticulum; mitochondrial matrix D Option D: inner mitochondrial membrane; mitochondrial matrix E Option E: outer mitochondrial membrane; cytosol
Option D: 3 NADH + FADH2 + GTP + 2CO2 + CoA
In the net reaction of the citric acid cycle, what are the products? A Option A: 3 NADH + FAD + GDP + 2CO2 + CoA B Option B: 3 NADH + FAD + GTP + 2CO2 + CoA C Option C: 3 NAD+ + FADH2 + GTP + 2CO2 + acetyl-CoA D Option D: 3 NADH + FADH2 + GTP + 2CO2 + CoA
Option A: 3 NAD+ + FAD + GDP + Pi + acetyl-CoA You got it right
In the net reaction of the citric acid cycle, what are the reactants? A Option A: 3 NAD+ + FAD + GDP + Pi + acetyl-CoA B Option B: 3 NAD+ + FAD + GTP + Pi + acetyl-CoA C Option C: 3 NAD+ + FADH2 + GDP + Pi + acetyl-CoA D Option D: 3 NADH + FAD + GDP + Pi + acetyl-CoA
False
Isocitrate lyase and malate synthase occur in both plants and animals. (T/F)
Glyoxylate
Isocitrate lyase cleaves isocitrate to succinate and __________ in the glyoxylate pathway
Option C: 1 GTP, 3 NADH, 1 FADH2 You got it right
One turn of the citric acid cycle generates A Option A: 2 FADH2, 3 ATP, 1 NADH B Option B: 1 NAD+, 2FADH2, 1 ATP C Option C: 1 GTP, 3 NADH, 1 FADH2 D Option D: 1 FAD, 2 ATP, 3 NADH E Option E: 1 FADH2, 1GTP, 2 NADH
True
Several biosynthetic pathways used citric aid cycle intermediates as starting material for anabolic reactions. (T/F)
Option B: Succinate and fumarate You got it right
Shown below is a list of pairs of compounds. In which pair is the second compound produced by an oxidation of the first compound? A Option A: Pyruvate and phosphoenolpyruvate B Option B: Succinate and fumarate C Option C: Oxaloacetate and malate D Option D: Phosphoenolpyruvate and 2-phosphoglycerate E Option E: 1,3-bisphosphoglycerate and glyceraldehyde-3-phosphate
oxaloacetate
Since ____________is produced in the final step and consumed in the first step, the citric acid cycle acts as a multistep catalyst that can oxidize an unlimited number of acetyl groups.
2
The citric acid cycle oxidizes the acetyl group of acetyl-CoA to ___________molecules of CO2.
Malonate
The compound ______ is a structural analog and competitive inhibitor of the enzyme succinate dehydrogenase.
Option B: malate synthase You got it right
The enzyme ______ is part of the glyoxylate cycle that occurs in plants, bacteria, and fungi.
Aconitase
The enzyme ______ is unique because it contains an iron sulfur cluster but does not participate in a redox reaction.
Option C: pyruvate decarboxylase You got it right
The figure below represents an intermediate in the reaction catalyzed by which of the following enzymes? A Option A: enolase B Option B: aldolase C Option C: pyruvate decarboxylase You got it right D Option D: glyceraldehyde-3-phosphate dehydrogenase E Option E: lactate dehydrogenase
Option D: Its reactions bypass the decarboxylation steps of the citric acid cycle. You got it right
The glyoxylate cycle in germinating seeds is a pathway that has some similarity to the citric acid cycle, but it uses the carbon-based products from the catabolism of fatty acids as the precursors for gluconeogensis. How can the glyoxylate cycle accomplish this? A Option A: It produces an excess of citrate, which is exported out of the mitochondria. B Option B: Its reactions take place partly in the matrix of the mitochondria and partly in the cytosol. C Option C: It uses only the catabolic products of saturated fatty acids with an even number of carbon atoms. D Option D: Its reactions bypass the decarboxylation steps of the citric acid cycle. E Option E: It prevents the formation of malate, which can form oxaloacetate.
Option C :converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized. You got it right
The isomerization of citrate to isocitrate A Option A :is the reaction of the citric acid cycle that occurs spontaneously without enzymatic catalysis. B Option B :protects cells from the toxic effects of arsenite ion. C Option C :converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized. D Option D :is one major regulatory step for the citric acid cycle because it functions as a rate limiting step.
True
The most crucial regulators of the citric acid cycle are its substrates, acetyl-CoA and oxaloacetate, and its product, NADH. (T/F)
Malate
The name of a citric acid cycle intermediate that is derived from the Latin word for "apple" is ______.
Option A: A. The ADP/ATP ratio is high. You got it right
The rate of the citric acid cycle would be INCREASED under which of the following conditions? A Option A: A. The ADP/ATP ratio is high. B Option B: B. The ADP/ATP ratio is low. C Option C: C. The NAD+/NADH ratio is low. D Option D: D. The concentration of oxaloacetate is low. E Option E: B and C.
Option D: succinate dehydrogenase You got it right
The reaction catalyzed by _____ requires an enzyme bound flavin coenzyme. A Option A: isocitrate dehydrogenase B Option B: α-ketoglutarate dehydrogenase C Option C: succinyl-CoA synthetase D Option D: succinate dehydrogenase E Option E: malate dehydrogenase
True
The thiamine pyrophosphate (TPP) cofactor is bound to E1 and decarboxylates pyruvate, yielding a hydroxyethyl TPP carbanion.
Option D: Malate dehydrogenase
Under standard state conditions, which enzyme of the citric acid cycle has the largest positive ∆G0'? A Option A: Citrate synthase B Option B: Aconitase C Option C: Isocitrate dehydrogenase D Option D: Malate dehydrogenase
Option C: When the NADH/NAD+ ratio is high. You got it right
Under which of the following conditions is the entry of acetyl-CoA into the citric acid cycle DECREASED? A Option A: When the ADP/ATP ratio is high. B Option B: When ADP levels are elevated. C Option C: When the NADH/NAD+ ratio is high. D Option D: When NADH is rapidly oxidized via the electron transport system. E Option E: When NAD+ levels are elevated.
True
Various dicarboxylates (a-ketoglutarate, succinate, and malate) and a tricarboxylate (citrate) are rapidly oxidized by muscle tissue during respiration. (T/F)
Option C: Aspartate and pyruvate You got it right
What compounds are produced when oxaloacetate undergoes transamination with alanine? A Option A: Glutamate and pyruvate B Option B: Glutamate and alpha-ketoglutarate C Option C: Aspartate and pyruvate D Option D: Aspartate and alpha-ketoglutarate
False
When glucose is converted to lactate or ethanol, a relatively oxidized product leaves the cell. (T/F)
Option B: CoA You got it right
Which cofactor of pyruvate dehydrogenase contains a sulfhydryl group? A Option A: Thiamine pyrophosphate (TPP) B Option B: CoA C Option C: NAD+ D Option D: FAD
Option B: Succinate dehydrogenase You got it right
Which enzyme of the citric acid cycle is strongly inhibited by malonate? A Option A: Succinyl-CoA synthetase B Option B: Succinate dehydrogenase C Option C: Fumarase D Option D: Citrate synthase
Option D: Malate dehydrogenase
Which enzyme of the citric acid cycle is very similar structurally and mechanistically to lactate dehydrogenase and alcohol dehydrogenase? A Option A: α-Ketoglutarate dehydrogenase B Option B: Succinate dehydrogenase C Option C: NAD+ -dependent isocitrate dehydrogenase D Option D: Malate dehydrogenase
Option C: histidine You got it right
Which of the following amino acid residues facilitates the transfer of a phosphate group in the reaction producing succinate and GTP? A Option A: aspartate B Option B: glutamate C Option C: histidine D Option D: lysine E Option E: serine
Option C: ii, iv and v You got it right
Which of the following are involved in the equation that best describes the oxidative decarboxylation of pyruvate? i. ATP ii. HS-CoA iii. H20 iv. NAD+v. CO2 vi. Oxaloacetate A Option A: i, ii, iv and vi B Option B: iii, iv and v C Option C: ii, iv and v D Option D: i, v and vi E Option E: ii and v
Option C: 2, 4 and 5 You got it right
Which of the following are involved in the equation that best describes the oxidative decarboxylation of α-ketoglutarate? 1) ATP 2) HS-CoA 3) H2O 4) NAD+ 5) CO2 6) Succinate A Option A: 1, 2, 4 and 6 B Option B: 1, 5 and 6 C Option C: 2, 4 and 5 D Option D: 2 and 5 E Option E: 3, 4 and 5
Option D :It allows recovery of energy from several metabolic fuels that are broken down to acetyl-CoA.
Which of the following best describes the importance of the citric acid cycle as a central pathway of metabolism? A Option A :It allows recovery of energy from carbohydrates only. B Option B :It allows recovery of energy from fatty acids only. C Option C :It allows recovery of energy from amino acids only. D Option D :It allows recovery of energy from several metabolic fuels that are broken down to acetyl-CoA.
Option A: The product always has the R configuration. You got it right
Which of the following can be said about the isocitrate product of aconitase? A Option A: The product always has the R configuration. B Option B: The product always has the S configuration. C Option C: The product is not chiral. D Option D: The product can exist in either the R or S configuration in eukaryotes. E Option E: If the product is in the R configuration it has by passed the cis-aconitate intermediate.
Option A :Elevated concentrations of NADH and ATP You got it right Option D :Elevated concentrations of acetyl-CoA
Which of the following causes pyruvate dehydrogenase kinase to catalyze the phosphorylation and inactivation of E1 in the pyruvate dehydrogenase complex? A Option A :Elevated concentrations of NADH and ATP You got it right B Option B :Elevated concentrations of NAD+ and ADP C Option C :Insulin D Option D :Elevated concentrations of acetyl-CoA
Option E: oxaloacetate
Which of the following citric acid cycle intermediates can be converted to aspartate via transamination? A Option A: citrate B Option B: α-ketoglutarate C Option C: succinate D Option D: fumarate E Option E: oxaloacetate
Option E: NAD+
Which of the following coenzymes is required by the pyruvate dehydrogenase complex for reoxidation of E3? A Option A: thiamine pyrophosphate B Option B: pyridoxal phosphate C Option C: coenzyme A D Option D: FAD E Option E: NAD+
Option B: i), iii), and v) You got it right
Which of the following compounds are used in a substrate-level phosphorylation reaction? i) 1,3-bisphosphoglycerate ii) glucose-6-phosphate iii) phosphoenolpyruvate iv) 3-phosphoglycerate v) succinyl-CoA A Option A: i) and iii) B Option B: i), iii), and v) C Option C: ii) and iv) D Option D: ii), iv), and v)
Option A: The reaction catalyzed by isocitrate dehydrogenase. You got it right
Which of the following enzymatic reactions is favorable both under physiological conditions and under standard conditions? A Option A: The reaction catalyzed by isocitrate dehydrogenase. B Option B: The reaction catalyzed by malate dehydrogenase. C Option C: The reaction catalyzed by succinate dehydrogenase. D Option D: all of the above E Option E: none of the above
Option B: i and iv You got it right
Which of the following enzymes catalyze oxidation reactions in the citric acid cycle? i. Succinate dehydrogenase. ii. Pyruvate dehydrogenase. iii. Glycerol-3-phosphate dehydrogenase. iv. α-Ketoglutarate dehydrogenase. A Option A: i, ii, and iv B Option B: i and iv You got it right C Option C: i, iii, and iv D Option D: All of the listed enzymes
Option B: Succinyl-CoA synthetase You got it right
Which of the following enzymes catalyzes a reaction with the pictured compound as an intermediate? A Option A: α-ketoglutarate dehydrogenase B Option B: Succinyl-CoA synthetase C Option C: Succinate dehydrogenase D Option D: Fumarase E Option E: Malate dehydrogenase
Option A: Succinate dehydrogenase. You got it right
Which of the following enzymes does not catalyze a regulated reaction? A Option A: Succinate dehydrogenase. B Option B: α-Ketoglutarate dehydrogenase. C Option C: Isocitrate dehydrogenase. D Option D: Pyruvate kinase. E Option E: Pyruvate carboxylase.
Option B :Isocitrate dehydrogenase You got it right
Which of the following enzymes of the citric acid cycle is inhibited by ATP? A Option A :Citrate synthase B Option B :Isocitrate dehydrogenase C Option C :α-ketoglutarate dehydrogenase D Option D :Succinyl-CoA synthetase
Option E: The proximity of the catalytic enzymes in the cluster slows down the overall rate.
Which of the following is FALSE with respect to the pyruvate dehydrogenase complex? A Option A: It is located in the mitochondrial matrix. B Option B: It is activated by Ca2+ ions. C Option C: It is inhibited by high levels of ATP and NADH. D Option D: It is a multienzyme complex. E Option E: The proximity of the catalytic enzymes in the cluster slows down the overall rate.
Option B: I, II, III You got it right
Which of the following is TRUE regarding the discovery of the citric acid cycle? I. One of the first discoveries was the involvement of coenzyme A in the production of GTP. II. Krebs had knowledge of the sequence of reactions before he was able to demonstrate the link of the cycle to glucose metabolism. III. The cycle is named after the product of its first reaction, citrate. IV. Krebs demonstrated the involvement of the citric acid cycle in oxidation of amino acid and fatty acids. A Option A: I, II, III, IV B Option B: I, II, III C Option C: II, III D Option D: III, IV E Option E: II, IV
Option E: cis-aconitate
Which of the following is an intermediate between citrate and isocitrate in the citric acid cycle? A Option A: succinyl-CoA B Option B: citryl-CoA C Option C: oxalosuccinate D Option D: succinyl-phosphate E Option E: cis-aconitate
Option C
Which of the following is oxidized by a multienzyme complex that requires five different coenzymes?
Option C: II only You got it right
Which of the following is(are) TRUE concerning the metabolic reaction shown below? Pyruvate + NAD+ + CoA-SH Acetyl-CoA + NADH + H+ + CO2 I. The enzyme that catalyzes this reaction contains a pyridoxal phosphate prosthetic group. II. This reaction is an oxidative decarboxylation. III. The enzyme that catalyzes this metabolic conversion is activated by high concentrations of ATP A Option A: I, II, III B Option B: II, III C Option C: II only D Option D: III only E Option E: I, II
Option C: 2-Phosphoglycerate You got it right
Which of the following molecules is not a high-energy molecule? A Option A: NADPH B Option B: Succinyl-CoA C Option C: 2-Phosphoglycerate D Option D: NADPH and 2-phosphoglycerate E Option E: Succinyl-CoA and 2-phosphoglycerate
Option D: mammals You got it right
Which of the following organisms does not utilize the glyxolate cycle? A Option A: trees B Option B: bacteria C Option C: fungi D Option D: mammals E Option E: All of the above utilize the glyxolate cycle when necessary.
Option D: I, III You got it right
Which of the following represents a point of regulation for the citric acid cycle?I. pyruvate dehydrogenase complexII. aconitaseIII. isocitrate dehydrogenaseIV. fumarase A Option A: I, II, III, IV B Option B: I, II, IV C Option C: II, III D Option D: I, III E Option E: I, IV
Option C: NADH is an allosteric activator of pyruvate dehydrogenase. You got it right
Which of the following statements about NADH is FALSE? A Option A: NAD+ is converted to NADH by α-ketoglutarate dehydrogenase. B Option B: NAD+ is converted to NADH by isocitrate dehydrogenase. C Option C: NADH is an allosteric activator of pyruvate dehydrogenase. D Option D: The oxidation of one molecule of NADH by the electron transport chain forms one molecule of water.
Option B: One of the products of this reaction is a molecule containing a thioester bond. You got it right
Which of the following statements about the oxidative decarboxylation of pyruvate is TRUE? A Option A: It only occurs under anaerobic conditions. B Option B: One of the products of this reaction is a molecule containing a thioester bond. C Option C: The reaction is so important to aerobic catabolism that the enzyme catalyzing it is activated under all cellular conditions. D Option D: The process occurs in the cytosol.
Option B: Lipoamide passes electrons through FADH2, which almost instantly passes them to NAD thus forming NADH. You got it right
Which of the following statements correctly and most accurately describes the function of FAD in the pyruvate dehydrogenase enzyme complex? A Option A: NADH passes electrons to FAD to form FADH2. B Option B: Lipoamide passes electrons through FADH2, which almost instantly passes them to NAD thus forming NADH. C Option C: FADH2 donates electrons to lipoamide thus regenerating FAD. D Option D: Lipoamide oxidizes NADH to NAD by passing electrons to FAD. E Option E: NAD accepts electrons directly from lipoamide, which has gained them via oxidation of FADH2
Option C: Succinyl-CoA synthetase captures the energy of a thioester bond and stores it in a phosphoester bond. You got it right
Which of the following statements is FALSE? A Option A: Isocitrate dehydrogenase catalyzes an oxidative decarboxylation reaction. B Option B: Succinyl-CoA synthetase and α-ketoglutarate dehydrogenase catalyze energy-capture steps in the citric acid cycle. C Option C: Succinyl-CoA synthetase captures the energy of a thioester bond and stores it in a phosphoester bond. D Option D: α-Ketoglutarate dehydrogenase and pyruvate dehydrogenase catalyze oxidative decarboxylations.
Option C: C. Acetyl-CoA activates pyruvate carboxylase. You got it right
Which of the following statements is/are TRUE regarding acetyl-CoA? A Option A: A. Acetyl-CoA activates pyruvate dehydrogenase. B Option B: B. Acetyl-CoA is considered a "high-energy" molecule because of its phosphoester bond. C Option C: C. Acetyl-CoA activates pyruvate carboxylase. D Option D: D. Acetyl-CoA activates α-ketoglutarate dehydrogenase. E Option E: Both A and D.
Option D: the reaction catalyzed by α-ketoglutarate dehydrogenase. You got it right
Which of the following steps of the citric acid cycle conserves the energy of a high energy thioester bond? A Option A: the reaction catalyzed by succinate dehydrogenase. B Option B: the reaction that produces oxaloacetate. C Option C: the condensation reaction that produces citrate. D Option D: the reaction catalyzed by α-ketoglutarate dehydrogenase. E Option E: the conversion of citrate to isocitrate.
Option D
Which of the following structures represents a molecule that is added to succinate to form CoA and malate?
Option C: lipoamide You got it right
Which of the following uses inherent length and flexibility to facilitate transfer of an acetyl group? A Option A: FAD B Option B: NAD+ C Option C: lipoamide D Option D: thiamine pyrophosphate E Option E: coenzyme A
Option D: I, II You got it right
Which of the following utilizes intermediates of the citric acid cycle? I. gluconeogenesis II. amino acid biosynthesis III. fatty acid oxidation IV. glycolysis Option A: I only Option B: II only Option C: I, II, III Option D: I, II Option E: I, IV
Option D: I, III, IV You got it right
Which of the following would decrease activity of the citric acid cycle overall? I. high concentration of NADH II. high concentration of Ca2+ III. high concentration of ATP IV. high concentration of citrate A Option A: I only B Option B: I, II, III, IV C Option C: I, III D Option D: I, III, IV E Option E: I, IV
Option C: succinyl CoA succinate You got it right
Which reaction below produces GTP in the citric acid cycle? A Option A: isocitrate -ketoglutarate B Option B: -ketoglutarate succinyl CoA C Option C: succinyl CoA succinate D Option D: fumarate malate E Option E: malate oxaloacetate
Option B: α-ketoglutarate to succinyl-CoA. You got it right
Which reaction of the citric acid cycle is most similar to the reaction catalyzed by the pyruvate dehydrogenase complex? A Option A: citrate to isocitrate. B Option B: α-ketoglutarate to succinyl-CoA. C Option C: succinyl-CoA to succinate. D Option D: fumarate to malate. E Option E: malate to oxaloacetate.
Option B: succinyl-CoA to succinate You got it right
Which reaction of the citric acid cycle produces a nucleoside triphosphate? A Option A: citrate to isocitrate B Option B: succinyl-CoA to succinate C Option C: succinate to fumarate D Option D: fumarate to malate E Option E: malate to oxaloacetate
Option B: 7 You got it right
Which reaction or reactions in the scheme of glycolysis and the citric acid cycle attached at the back of this exam will NOT proceed in the absence of inorganic phosphate ions? Option A: 1 and 3 Option B: 7 You got it right Option C: 8 and 11 Option D: 12 and 16
Option D: Succinate to oxaloacetate
Which segment of the citric acid cycle is used in the glyoxylate pathway? A Option A: Oxaloacetate to isocitrate B Option B: Citrate to Succinyl-CoA C Option C: Succinate to malate D Option D: Succinate to oxaloacetate
Option A: 1, 2 and 3 You got it right
Which three of the following are possible sources for acetyl-CoA that enters the citric acid cycle? 1) oxidative decarboxylation of pyruvate 2) β oxidation of fatty acids 3) catabolism of certain amino acids 4) citrate 5) carboxylation of pyruvate A Option A: 1, 2 and 3 B Option B: 1, 2 and 5 C Option C: 1, 2 and 4 D Option D: 2, 3 and 4 E Option E: 1, 4 and 5
Option C: Because it produces reduced electron carriers, which are re-oxidized by transferring their electrons ultimately to oxygen. You got it right
Why is the citric acid cycle considered to be part of aerobic metabolism even though oxygen does not explicitly appear in any reaction? A Option A: Because it takes place in the mitochondrion. B Option B: Because it contains oxidation reactions. C Option C: Because it produces reduced electron carriers, which are re-oxidized by transferring their electrons ultimately to oxygen. D Option D: Because NADH and FADH2 produce lots of ATP when re-oxidized. E Option E: Because it produces carbon dioxide.
Carbon Dioxide
_____ and pyruvate can be combined in an ATP dependent reaction that regenerates one of the key intermediates in the citric acid cycle.
Succinyl CoA synthetase
_____ catalyzes a substrate-level phosphorylation reaction within the citric acid cycle.
isocitrate
______ is the first compound that is oxidized in the citric acid cycle.
Oxaloacetate
______ is used in the first reaction of the citric acid cycle and regenerated upon completion of one turn of the citric acid cycle.
Cataplerotic
_______ reactions drain the citric acid cycle of intermediates.
Citrate
_________ synthase is an enzyme of the citric acid cycle that is inhibited by NADH.
Amino Acid
____________- biosynthesis uses alpha-ketoglutarate and oxaloacetate as starting materials.
Plants
____________- possess enzymes that mediate the net conversion of acetyl-CoA to oxaloacetate, which can be used for gluconeogenesis
alpha-ketoglutarate dehydrogenase
_______________ produces the second CO2 and NADH of the citric acid cycle.
True
α-Ketoglutarate dehydrogenase is a multienzyme complex containing alpha-ketoglutarate dehydrogenase (E1), dihydrolipoyl transsuccinylase (E2), and dihydrolipoyl dehydrogenase (E3). (T/F)
