Chp. 14 The Citric Acid Cycle
Each round of the citric acid cycle generates _____ NADH, _____ QH2, and ____ GTP/ATP.
-3 -2 -1
What are the products of Pyruvate Dehydrogenase Reaction?
-Acetyl-CoA -CO2 -NADH
Citrate Synthase undergoes a _________ change upon binding Oxaloacetate allowing for binding of _________.
-Conformational -Acetyl-CoA
What other molecules are used to make acetyl-CoA?
-Fatty acids -Ketogonic amino acids -Ketones -Alcohol
What are the Products of the Citric Acid Cycle?
1 ATP 2CO2 3 NADH 1 FADH2 (QH2)
What are the 5 coenzymes of Pyruvate Dehydrogenase?
1. TPP-Vitamin B1 2. NAD+ 3. FAD 4. CoA 5. Lipoic Acid
What are the 5 CoEnzymes used in Pyruvate Dehydrogenase?
1. Thiamine Pyrophosphate (TPP) 2. NAD+ 3. FAD 4. CoA 5. Lipoic Acid
For Every 1 QH2 you get _____ ATP
1.5
For every 1 NADH you get ___ ATP
2.5
Carbons released from the Citric Acid Cycle are released from the Acetyl-CoA in the ________ of the Citric Acid Cycle. Not in the ________.
2nd round 1st round
Flux through the Citirc acid cycle is regulated primarly by feedback inhibition. There are ____ steps that are regulated.
3
How many carbons does Oxaloacetate have?
4
How many coenzyemes does the pyruvate dehydrognease complex have?
5
The pyruvate dehydrognase complex works in ______ steps
5
How many reactions does the Citric Acid Cycle have?
8
Citrate synthase binds which substrate first? A)Oxaloacetate B)Acetyl-CoA
A
How many NADH are oxidized in one turn of the TCA cycle? A)0 B)1 C)2 D)3 E)4
A
The Pasteur effect relates to the observation that the rate of glucose consumption is _____ during anaerobic catabolism. A)Increased B)Decreased
A
Which of the enzymes of the TCA cycle contain a FAD cofactor? A)Succinate dehydrogenase B)Malate dehydrogenase C)Succinyl-CoA synthetase D)α-ketoglutarate dehydrogenase E)Isocitrate dehydrogenase
A
Which of the enzymes of the TCA cycle contain an FAD cofactor? A. succinate dehydrogenase B. malate dehydrogenase C. isocitrate dehydrogenase D. a-ketoglutarate dehydrogenase
A
Which of the following terms describes the TCA cycle as both catabolic and anabolic? A. Anaplerotic B. Amphipathic
A
What are some common activators in the Citric Acid Cycle?
ADP Ca2+
What is the intermediate that forms in the Aconitase reaction?
Aconitate
What molecules inhibit and activate the regulator enzyme, a-Ketoglutarate?
Activate= ADP, Ca2+ Deactivate= ATP, NADH, Succinyl-CoA
What molecules inhibit and activate the regulator enzyme, Isocitrate Dehydrogenase?
Activate= ADP, NAD+ Deactivate= ATP, NADH
Flux through the TCA cycle is regulated at the _____ steps. A. near-equilibrium B. irreversible
B
Mammalian TCA enzymes are located in the: A)Cytosol B)Mitochondrial matrix C)Inner mitochondrial matrix D)Golgi apparatus E)Nucleus
B
The removal of 3 carbon atoms from pyruvate as 3 CO2molecules all involve A)Reductive carboxylations B)Oxidative decarboxylations C)Oxidative dehydrogenations D)Reductive hydrogenations E)None of the above
B
The two carbon atoms that enter the TCA cycle as acetyl-CoA are released as two CO2 molecules in the same round of the cycle. A)True B)False
B
Which of the following is NOT a cofactor in the pyruvate dehydrogenase complex? A)Thiamine pyrophosphate B)Coenzyme Q C)Lipoamide D)FAD
B
Which reaction in the TCA cycle uses a symmetrical molecule as a substrate? A)Step 1 B)Step 2 C)Step 3 D)Step 4 E)Step 5
B
Which reactions in the TCA cycle use a thioester substrate (a substrate with acetyl-CoA attached)? A. Steps 1 and 3 B. Steps 1 and 5 C. Steps 2 and 3
B
Berberi is a disease that results from a lack of the vitamin thiamine, the precursor to thiamine pyrophosphate. What two intermediates accumulate in individuals with Beriberi? A)Oxaloacetate and pyruvate B)Acetyl-CoA and α-ketoglutarate C)Pyruvate and α-ketoglutarate D)All of the above E)None of the above
C
During the oxidation of acetyl-CoA through the TCA cycle, which steps involve oxidative decarboxylations? A. Step 3 B. Step 4 C. Both
C
Which enzyme of the pyruvate dehydrogenase complex is responsible for regenerating an oxidized lipoamide cofactor? A)E1 B)E2 C)E3 D)E4
C
Which of the following cofactors functions as a swinging arm within the pyruvate dehydrogenase complex? A)Thiamine pyrophosphate B)FAD C)Lipoamide D)NAD+
C
Which reaction in the TCA cycle gives electrons to ubiquinone? A. Step 2 B. Step 4 C. Step 6
C
Which reactions in the TCA cycle release CO2? A. Steps 1 and 2 B. Steps 5 and 6 C. Steps 3 and 4
C
How many NADH are produced when one acetyl group is oxidized in the TCA cycle? A)1 B)2 C)3 D)4 E)> 4
C (reaction 3,4,8)
What does an acetyl group consist of?
C--C==O
_______ adds an acetyl group to Oxaloacetate? (Enzyme)
Citrate Synthase
_______ is one of a few enzymes that can synthesize a C--C bond without a metal Ion Cofactor.
Citrate Synthase
What is the purpose of all the reactions that collectively make up the citric acid cycle?
Complete oxidation of carbons in intermediates to CO2 so that reduction reactions can be coupled with CO2 formation, thus forming energy carriers such as NADH and FADH2 for the electron transport chain
During the oxidation of acetyl-CoA through the TCA cycle, which steps involve oxidative decarboxylations? A)Step 3 of TCA B)Step 4 of TCA C)Step 6 of TCA D)A and B E)A, B, and C
D
The regulated enzymes of the TCA cycle include A)Malate dehydrogenase B)Fumarase C)Citrate lyase D)α-ketoglutarate dehydrogenase E)None of the above
D
The regulated enzymes of the TCA cycle include; A. Malate dehydrogenase B. Fumarase C. Citrate lyase D. a-ketoglutarate dehydrogenase
D
The ubiquitous chemistry of acetyl-CoA is centered on its high-energy _____ bond. A)Phosphothioester B)Ester C)Phosphoanhydride D)Thioester E)Phosphoester
D
Which of the following terms describes the TCA cycle as both catabolic and anabolic? A)Cataplerotic B)Amphibole C)Amphipathic D)Anaplerotic
D
Which reaction in the TCA cycle directly generates a high energy phosphodiester bond? A)Step 2 B)Step 3 C)Step 4 D)Step 5 E)Step 6
D
Which reaction(s) in the TCA cycle is (are) regulated by feedback inhibition? A)Step 1 B)Step 3 C)Step 4 D)A and C E)B and C
D
Which reactions in the TCA cycle release CO2? A)Steps 1 and 3 B)Steps 1 and 4 C)Steps 2 and 3 D)Steps 3 and 4 E)Steps 5 and 6
D
Malonate is a competitive inhibitor of succinate dehydrogenase. What TCA intermediates accumulate if malonate is present in a preparation of isolated mitochondria? A)Succinate B)Succinyl-CoA C)α-ketoglutarate D)A and B E)A, B, and C
E
Which TCA cycle intermediate is found at both the beginning and end of the cycle? A)Malate B)α-ketoglutarate C)Isocitrate D)Citrate E)Oxaloacetate
E
Which active site residues participate in the citrate synthase reaction? A)Ser B)His C)Asp D)A and C E)B and C
E
Which of the following can dispose of carbon atoms through the TCA cycle? A)Carbohydrates B)Fatty acids C)Amino acids D)A and C E)All of the above
E
Which reaction in the TCA cycle gives electrons to ubiquinone?A)Step 2 B)Step 3 C)Step 4 D)Step 5 E)Step 6
E
Which reactions in the TCA cycle use a thioester substrate? A)Steps 1 and 3 B)Steps 1 and 4 C)Steps 2 and 3 D)Steps 2 and 4 E)Steps 1 and 5
E
What is a Thioester bond?
High-energy bond formed by a condensation reaction between an acid (acyl) group and a thiol group (-SH);
What enzyme catalyzes the rate-limiting step of the citric acid cycle?
Isocitrate Dehydrogenase
Which is the "swinging arm" cofactor?
Lipoamide
What coenzyme does step 2 use of Pyruvate Dehydrogenase?
Lipoic Acid
What part of the cell are mammalian Citric Acid Cycle enzymes located?
Mitochondrial Matrix
What is the Pyruvate Dehydrogenase Complex?
Pyruvate + CoA + NAD+ yields Acetyl-CoA + CO2 + NADH
What is the name of the reaction that converts Pyruvate to Acetyl-CoA?
Pyruvate Dehydrogenase reaction
What is anaplerotic reactions
Reactions that help replenish intermediates in the tricarboxylic acid cycle when their reserves are depleted.
Which step is this in? E2 is restored
Step 4 of Pyruvate Dehydrogenase
Which enzyme is located in the Inner Mitochondrial Matrix?
Succinate Dehydrogenase
What coenzyme is used in step 1 of Pyruvate Dehydrogenase?
TPP
Vitamin B1 is also known as
Thiamine
Succinate Dehydrogenase generates _______.
Ubiquinol
Which of the following answers complete the sentence correctly? Succinate dehydrogenase... a. is an integral membrane protein unlike the other enzymes of the citric acid cycle. b. contains FAD and NAD+ cofactors like pyruvate dehydrogenase. c. is a copper-sulfur protein d. carries out an oxidative decarboxylation like isocitrate dehydrogenase.
a
What molecules inhibit and activate the regulator enzyme, Citrate Synthase?
activate= none Deactivate= ATP, NADH, Succinyl-CoA, Citrate
During exercise, some pyruvate can be converted to _________ to boost the activity of the citric acid cycle.
alpha-ketoglutarate
What is the Pasteur effect?
ask Dr. Anderson
The Citric Acid Cycle is an ______ generating cycle.
energy
What does a lipoamide consist of?
lipoic acid Lysine
Where does conversion of pyruvate to acetyl-CoA occur in the cell?
mitochondrial matrix
In the Citric acid Cycle, we start with _______ as the starting substrate
oxaloacetate
The Citric acid cycle intermediates are all ______ of other molecules.
precursors
Decarboxylation of pyruvate occurs in which step of Pyruvate Dehydrogenase?
step 1
Which step of the Citrate Synthase Mechanism is this? (Step 1 of Citric Acid Cycle) Oxaloacetate and then acetyl-CoA bind to the enzyme.
step 1
Which steps are regulated in the Citric Acid Cycle?
step 1 step 3 step 4
Which step is this in? E1 decarboxylates pyruvate; CO2 is released
step 1 of Pyruvate Dehydrogenase
Regulation occurs at 3 irreversible steps:
step 1- Citrate Synthase Step 3 Isocentrate Dehydrogenase Step 4- alpha-Ketoglutarate
What are the 3 irreversible steps?
step 1- Citrate Synthase Step 3 Isocentrate Dehydrogenase Step 4- alpha-Ketoglutarate
Which step of the Citrate Synthase Mechanism is this? (Step 1 of Citric Acid Cycle) Asp 375, a base removes a proton from the acetyl group to produce an enolate, which is stabilized by a hydrogen bond to His 274.
step 2
Which step is this in? A leftover hydroxyethyl group is transferred to E2
step 2 of Pyruvate Dehydrogenase
Which step in the Citric Acid Cycle is the first CO2 released?
step 3
Which step of the Citrate Synthase Mechanism is this? (Step 1 of Citric Acid Cycle) The enolate attacks oxaloacetate to produce a citryl-CoA intermediate
step 3
Which step is this in? An acetyl group is transferred to CoA
step 3 of Pyruvate Dehydrogenase
Which step in the Citric Acid Cycle is the second CO2 released?
step 4
Which step of the Citrate Synthase Mechanism is this? (Step 1 of Citric Acid Cycle) Hydrolysis releases CoA and citrate
step 4
Which step is this in? E3 uses a disulfide bond and an FAD cofactor
step 4 of Pyruvate Dehydrogenase
Which step is this in? Lopoamide is oxidized by E3's disulfide
step 4 of Pyruvate Dehydrogenase
Which step is this in? E3 is restored and NADH is produced
step 5 of Pyruvate Dehydrogenase
Which step is this in? Electrons move from FADH2 to NAD+ to form NADH and H+
step 5 of Pyruvate Dehydrogenase
Which step is this in? Electrons move to FAD to form FADH2
step 5 of Pyruvate Dehydrogenase
Can citrate and Pyruvate cross the mitochondrial membrane? How?
yes, via specific transport proteins
