Week 8
One turn of the citric acid cycle generates - 2 FADH2, 3 ATP, 1 NADH - 1 NAD+, 2FADH2, 1 ATP - 1 GTP, 3 NADH, 1 FADH2 - 1 FAD, 2 ATP, 3 NADH - 1 FADH2, 1GTP, 2 NADH
1 GTP, 3 NADH, 1 FADH2
How many NADH are produced when one acetyl group is oxidized in the citric acid cycle? - 1 - 2 - 3 - 4 - more than 4
3
After passing through the citric acid cycle, one mole of pyruvate will result in the formation of ________ moles of carbon dioxide and ________ mole(s) of ATP (or GTP). - 2; 2 - 2; 1 - 3; 2 - 3; 1
3; 1
How many electrons are transferred from one acetyl group during the citric acid cycle? - 2 - 4 - 6 - 8 - 10
8
Which statement about myosin is not true? - Myosin is a heterohexamer. - Myosin contains two globular heads. - Myosin contains six different polypeptides - Myosin aggregates to form thick filaments - All of the answers above are true of myosin.
All of the answers above are true of myosin.
ATP is consumed by the pyruvate dehydrogenase complex during the synthesis of acetyl CoA. - True - False
False
The activity of dihydrolipoamide acetyltransferase (E2) is inhibited when the concentration of of acetyl CoA is decreased - True - False
False
The immediate electron acceptor for the majority of the oxidative reactions of the citric acid cycle is - ATP - NAD - FAD - coenzyme A
NAD
Which of the following enzymes does not use NAD+ for oxidation? - Alpha-Ketoglutarate Dehydrogenase complex. - IsoCitrate Dehydrogenase. - Succinate Dehydrogenase. - Malate Dehydrogenase. - All of these enzymes use NAD+
Succinate Dehydrogenase.
In muscle cells, the following reaction proceeds as written, i.e., from left to right, despite having ΔG°' ≈ +30 kJ/mol. How can this occur? malate + NAD+ → oxaloacetate + NADH + H+ - It is obviously thermodynamically favored under standard conditions. - In the cell, it is kinetically favored, even though it's thermodynamically unfavored. - The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell. - [H+] must be higher in muscle than under standard conditions, thus altering ΔG°' to ΔG°.
The concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell.
All but one of the enzymes of the citric acid cycle are found in this part of the mitochondrion: - The outer membrane. - The inner membrane. - The mitochondrial matrix. - The intermembrane space. - It is not known where these enzymes are located.
The mitochondrial matrix.
Release of succinate from succinyl-CoA can be coupled to GTP synthesis because: - The amide bond between succinate and CoA has a large−ΔG of hydrolysis. - The thioester bond between succinate and CoA has a large −ΔG of hydrolysis. - The link between succinate and CoA involves an acid anhydride to phosphate. - Coenzyme A is a "high energy" compound, just like GTP. - None of these explains why GTP can be formed during this reaction.
The thioester bond between succinate and CoA has a large −ΔG of hydrolysis
Pyruvate translocase is specific for transporting pyruvate across the inner mitochondrial membrane. - True - False
True
The activity of dihydrolipoamide dehydrogenase (E3) is inhibited by a high NADH/NAD+ ratio. - True - False
True
The citric acid cycle can be viewed as a multi-step catalyst simply because it returns to its original state after each round of reactions. - True - False
True
The pyruvate dehydrogenase complex is composed of three distinct enzymes. - True - False
True
When acetyl-CoA reacts with oxaloacetate to form citrate - a new carbon-carbon bond is formed - an oxidative decarboxylation reaction takes place - a dehydration reaction takes place - a rearrangement takes place
a new carbon-carbon bond is formed
The acetyl group is carried on lipoic acid as - an alcohol. - a thioester. - a phosphoanhydride. - an amide.
a thioester.
Which 5-carbon intermediate of the citric acid cycle is converted to a 4-carbon molecule with the release of carbon dioxide? - fumarase - a-ketoglutarate - succinate - isocitrate
a-ketoglutarate
Condensation of ____ with oxaloacetate yield citrate. - acetyl-CoA - α-ketoglutarate - isocitrate - citrophosphate - oxalosuccinate
acetyl-CoA
Which of the following condenses with oxaloacetate to form citrate? - acetyl-CoA - cis-aconitate - oxalosuccinate - succinyl-phosphate - carboxybiotin
acetyl-CoA
Which enzyme catalyzes the conversion of citrate to isocitrate? - aldolase - citrate synthase - citrate isomerase - aconitase
aconitase
Which of the following enzymes is not a control point of the citric acid cycle? - citrate synthase - isocitrate dehydrogenase - aconitase - the α-ketoglutarate dehydrogenase complex
aconitase
Each myosin head contains a binding site for _____ and a binding site for _____. - tubulin; GTP - another myosin molecule; ATP - kinesin; GTP - actin; ATP - none of the above
actin; ATP
The step at which acetyl CoA enters the citric acid cycle is classified as a ________ reaction. - condensation - substrate-level phosphorylation - decarboxylation - dehydrogenation
condensation
Which of the following causes pyruvate dehydrogenase kinase to catalyze the phosphorylation and inactivation of E1 in the pyruvate dehydrogenase complex? - elevated concentrations of NADH and ATP - elevated concentrations of NAD+ and ADP - insulin - elevated concentrations of acetyl-CoA - C and D
elevated concentrations of NADH and ATP
Each of the following catalyzed reactions of the citric acid cycle appears to be regulated except - citrate synthase. - fumarase. - isocitrate dehydrogenase. - a-ketoglutarate dehydrogenase complex.
fumarase.
What type of reaction is the conversion of fumarate to malate? - oxidative decarboxylation - hydration - dehydrogenation - condensation
hydration
What makes the reaction catalyzed by citrate synthase highly exergonic? - hydrolysis of thioester - conversion from keto to enol tautomer - hydrolysis of ATP - decarboxylation reaction - hydrolysis of GTP
hydrolysis of thioester
Muscle contraction is triggered - in response to an increase in the cytoplasmic Ca2+ concentration. - in response to a decrease in the cytoplasmic Ca2+ concentration. - in response to an increase in the cytoplasmic cAMP concentration. - in response to a decrease in the cytoplasmic cAMP concentration. - in response to an increase in the cytoplasmic titin concentration.
in response to an increase in the cytoplasmic Ca2+ concentration.
The enzyme pyruvate translocase is located ________. - in the cytosol - in the inner mitochondrial membrane - in the mitochondrial matrix - in the endoplasmic reticulum
in the inner mitochondrial membrane
Which enzymes in the citric acid cycle catalyze oxidative decarboxylation reactions? - isocitrate dehydrogenase and the α-ketoglutarate dehydrogenase complex - aconitase and succinate dehydrogenase - the α-ketoglutarate dehydrogenase complex and succinate thiokinase - fumarase and succinate dehydrogenase
isocitrate dehydrogenase and the α-ketoglutarate dehydrogenase complex
In eukaryotes the enzymes of the citric acid cycle are found in the ________. - cytosol - mitochondria - nucleus - endoplasmic reticulum
mitochondria
Where is succinate dehydrogenase located? - mitochondrial matrix - mitochondrial inner membrane - mitochondrial inter-membrane space - mitochondrial outer membrane - none of the above
mitochondrial inner membrane
What cellular location contains pyruvate dehydrogenase and most of the citric acid cycle enzymes? - outer mitochondrial membrane - mitochondrial inter-membrane space - inner mitochondrial membrane - cytosol - mitochondrial matrix
mitochondrial matrix
In eukaryotes, the citric acid cycle occurs in the _____ and therefore requires that reactants of the citric acid cycle be transported from the _____. - cytosol; mitochondrial matrix - mitochondrial matrix; cytosol - endoplasmic reticulum; mitochondrial matrix - inner mitochondrial membrane; mitochondrial matrix - outer mitochondrial membrane; cytosol
mitochondrial matrix; cytosol
The energy needed to drive muscle contraction comes from ATP hydrolysis that is carried out by - G-actin. - F-actin. - myosin heads. - myosin tails. - tropomyosin.
myosin heads.
A deficiency in thiamine causes the disease beriberi. Which might you expect to have a higher than normal blood concentration in an individual with this condition? - isocitrate - pyruvate - oxaloacetate - acetyl CoA
pyruvate
Which of the following inhibit(s) pyruvate dehydrogenase kinase? - pyruvate - NADH - acetyl-CoA - All of these
pyruvate
The reaction catalyzed by _____ requires an enzyme bound flavin coenzyme. - isocitrate dehydrogenase - α-ketoglutarate dehydrogenase - succinyl-CoA synthetase - succinate dehydrogenase - malate dehydrogenase
succinate dehydrogenase
Which of the following enzymes contains an FAD prosthetic group? - succinate dehydrogenase - isocitrate dehydrogenase - α-ketoglutarate dehydrogenase - malate dehydrogenase - pyruvate dehydrogenase
succinate dehydrogenase
Which of the following enzymes uses coenzyme FAD as the electron acceptor? - isocitrate dehydrogenase - succinate dehydrogenase - aconitase - malate dehydrogenase
succinate dehydrogenase
Which reaction below produces GTP in the citric acid cycle? - isocitrate to α-ketoglutarate - α-ketoglutarate to succinyl CoA - succinyl CoA to succinate - fumarate to malate - malate to oxaloacetate
succinyl CoA to succinate
Pyruvate translocase is a/an ________ protein that transports ________. - antiport; pyruvate and H+ in opposite directions - uniport; only pyruvate - symport; pyruvate and H+ in the same direction - antiport; pyruvate and CO2 in opposite directions
symport; pyruvate and H+ in the same direction
The succinate dehydrogenase complex catalyzes - the formation of a single hydrogen bond in the oxidation of succinate to fumarate. - the formation of a double bond in the oxidation of succinate to fumarate. - Both the formation of a single hydrogen bond in the oxidation of succinate to fumarate and the formation of a double bond in the oxidation of succinate to fumarate - None of these
the formation of a double bond in the oxidation of succinate to fumarate.
In which cellular location do the majority of the reactions of the citric acid cycle take place? - the cytosol. - the mitochondrial matrix. - the endoplasmic reticulum. - lysosomes.
the mitochondrial matrix.
The arrangement of subunits in the PDH(pyruvate dehydrogenase) complex ensures that ________. - ATP is formed - the product of one enzyme is delivered to the next in turn - the dihydrolipoamide arm can react with NAD+ - acetyl CoA enters into the series of reactions
the product of one enzyme is delivered to the next in turn
A control point outside the citric acid cycle is the reaction catalyzed by - the pyruvate dehydrogenase complex. - citrate synthetase. - isocitrate dehydrogenase. - the α-ketoglutarate dehydrogenase complex.
the pyruvate dehydrogenase complex.
The repeating functional unit in a myofibril is called - the A band. - the I band. - the sarcomere. - the H zone. - the M disk.
the sarcomere.
Which of the following coenzymes is required by E1 of the pyruvate dehydrogenase complex for catalytic activity? - thiamine pyrophosphate - lipoamide - coenzyme A - NAD+ - FAD
thiamine pyrophosphate
The order of prosthetic groups as they act in the three proteins of the PDH(pyruvate dehydrogenase) complex is: - FAD thiamine pyrophosphate NAD+ - FAD thiamine pyrophosphate dihydrolipoamide - thiamine pyrophosphate dihydrolipoamide FAD - NAD+ FAD dihydrolipoamide
thiamine pyrophosphate dihydrolipoamide FAD
In a muscle cell, what is the name for the bundles of myosin tails? - cytoskeleton - thick filaments - intermediate filaments - thin filaments - none of the above
thick filaments
