Lecture 20

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Where does the citric acid cycle occur in eukaryotes?

Mitochondrial inner membrane

Plasma membrane

Cytoplasm

Mitochondrial matrix (correct)

Which of the following leads to the production of Acetyl CoA?

Glycolysis

Oxidative phosphorylation

Electron Transport Chain (ETC)

Fatty acid oxidation (correct)

What is the main role of the pyruvate dehydrogenase complex (PDH) in cellular respiration?

Production of ATP

Formation of NAD+

Reduction of Acetyl CoA

Conversion of pyruvate to Acetyl CoA (correct)

In which stage of cellular respiration does the conversion of pyruvate to Acetyl CoA occur?

Stage 1: Production of Acetyl-CoA Signup and view all the answers

Which statement about the respiratory chain in oxidative phosphorylation is correct?

It ultimately reduces O2 to H2O Signup and view all the answers

What drives the production of ATP in oxidative phosphorylation?

Electron flow through the respiratory chain Signup and view all the answers

What is responsible for the reduction of the alkane to alkene in the Electron Transport Chain?

FADH2 Signup and view all the answers

Which enzyme catalyzes the hydration of fumarate to malate?

Fumarase Signup and view all the answers

What type of bond does fumarase always create during the hydration of fumarate to malate?

L-sugars Signup and view all the answers

Which of the following is NOT a reason why intermediates react quickly in the Citrate Synthase and Malate DHase metabolon?

They are protected from cellular degradation pathways Signup and view all the answers

Which of the following statements about the citric acid cycle is NOT true?

It has a net gain of carbon atoms Signup and view all the answers

In which step(s) of the citric acid cycle is energy conserved by electron transfer to FAD or NAD+, forming FADH2 or NADH + H+?

Steps 3, 4, and 6 Signup and view all the answers

Which of the following statements about the reversibility of steps in the citric acid cycle is true?

Steps 1, 3, and 4 are irreversible, while all other steps are reversible Signup and view all the answers

Which of the following statements about the product of step 5 in the citric acid cycle is true?

The product may be either ATP or GTP, depending on the isozyme catalyst Signup and view all the answers

What is the main similarity between the reaction converting α-ketoglutarate to succinyl-CoA and the pyruvate dehydrogenase reaction?

Both reactions result in the generation of NADH. Signup and view all the answers

Which complex is similar in structure and function to the pyruvate dehydrogenase complex?

α-Ketoglutarate dehydrogenase complex Signup and view all the answers

What is a key feature of the oxidative decarboxylation process catalyzed by the α-Ketoglutarate dehydrogenase complex?

Net full oxidation of all carbons of glucose Signup and view all the answers

Which statement accurately describes succinyl-CoA?

It is a higher-energy thioester bond. Signup and view all the answers

What role does product inhibition play in the regulation of the α-Ketoglutarate dehydrogenase complex?

Stops the enzyme activity when enough product is formed Signup and view all the answers

What is the purpose of the oxidative decarboxylation reaction catalyzed by isocitrate dehydrogenase?

To generate NADH and remove a carbon as CO2 from the citric acid cycle Signup and view all the answers

What is the purpose of the aconitase enzyme in the citric acid cycle?

Aconitase catalyzes the conversion of citrate to cis-aconitate, which is then converted to isocitrate Signup and view all the answers

Which statement is true about the carbon atoms lost as CO2 during the oxidative decarboxylation of isocitrate?

The carbon atoms lost as CO2 come from the breakdown of isocitrate, not from the acetyl-CoA or pyruvate Signup and view all the answers

What is the primary function of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

To act as a carrier of both hydrogen and an acetyl group Signup and view all the answers

Which of the following statements accurately describes the role of the lipoyl-lysine residue in the transfer of the acetyl group to coenzyme A?

The lipoyl-lysine residue accepts the acetyl group from TPP and transfers it to dihydrolipoyl transacetylase (E2) Signup and view all the answers

Which of the following statements accurately describes the role of the lipoyl-lysine residue in the oxidation-reduction reactions of the pyruvate dehydrogenase complex?

The lipoyl-lysine residue cycles between oxidized (disulfide) and reduced (dithiol) forms, facilitating the transfer of electrons Signup and view all the answers

What is the purpose of the long, flexible arms formed by cofactors like lipoate, biotin, and the combination of β-mercaptoethylamine and pantothenate?

To act as tethers that move intermediates from one active site to the next Signup and view all the answers

How does the lipoyllysyl moiety contribute to the pyruvate dehydrogenase complex?

Participating in the transfer of active aldehyde groups Signup and view all the answers

In the pyruvate decarboxylation process, what is the role of the dihydrolipoyl transacetylase enzyme?

Facilitating the formation of acetyl CoA Signup and view all the answers

What is the significance of the oxidized form of the lipoyl residue in accepting the acetyl group?

Enables the oxidation of the active aldehyde group Signup and view all the answers

How does the lipoyl group act as a carrier during the pyruvate decarboxylation process?

Transfers hydrogen and an acetyl group simultaneously Signup and view all the answers

What is the primary role of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

To accept the acetyl group from the oxidative decarboxylation of pyruvate and transfer it to coenzyme A. Signup and view all the answers

What is the role of FAD in the reoxidation of the lipoamide cofactor in the pyruvate dehydrogenase complex?

FAD acts as an electron acceptor, becoming reduced to FADH2 as the reduced lipoamide is reoxidized. Signup and view all the answers

What is the primary role of the dihydrolipoyl dehydrogenase (E3) enzyme in the pyruvate dehydrogenase complex?

To reoxidize the reduced lipoamide cofactor by transferring electrons to FAD, which is then reoxidized by NAD+. Signup and view all the answers

What is the role of thiamine pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

TPP catalyzes the decarboxylation of pyruvate, forming the acetyl group that is then transferred to the lipoyl-lysine residue. Signup and view all the answers

What is the primary role of the dihydrolipoyl transacetylase (E2) enzyme in the pyruvate dehydrogenase complex?

To transfer the acetyl group from the lipoyl-lysine residue to coenzyme A, forming acetyl-CoA. Signup and view all the answers

In the pyruvate dehydrogenase complex, which enzyme is responsible for the decarboxylation of pyruvate?

Pyruvate dehydrogenase (E1) Signup and view all the answers

What is the role of the lipoyl-lysine residue in the pyruvate dehydrogenase complex?

It transfers the acetyl group from TPP to coenzyme A. Signup and view all the answers

What is the function of dihydrolipoyl dehydrogenase (E3) in the pyruvate dehydrogenase complex?

It oxidizes the reduced lipoyl groups of E2 using NAD+. Signup and view all the answers

What is the role of thiamine pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

It acts as a cofactor for the decarboxylation of pyruvate. Signup and view all the answers

Which enzyme in the pyruvate dehydrogenase complex catalyzes the transfer of the acetyl group from the lipoyl-lysine residue to coenzyme A?

Dihydrolipoyl transacetylase (E2) Signup and view all the answers

What is the primary role of the dihydrolipoyl dehydrogenase (E3) enzyme in the pyruvate dehydrogenase complex?

To reoxidize the reduced lipoamide cofactor using NAD+ as the electron acceptor Signup and view all the answers

What is the primary function of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

To act as a flexible arm that shuttles the acetyl group from the pyruvate dehydrogenase (E1) enzyme to the dihydrolipoyl acetyltransferase (E2) enzyme Signup and view all the answers

What is the role of thiamine pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

To remove a carbon in the form of CO2 and create a 2-carbon acetyl group during the decarboxylation of pyruvate Signup and view all the answers

What is the main similarity between the reaction converting α-ketoglutarate to succinyl-CoA and the pyruvate dehydrogenase reaction?

Both reactions involve the removal of a carboxyl group as CO2 Signup and view all the answers

What is the role of the lipoyl-lysine residue in the transfer of the acetyl group to Coenzyme A?

The lipoyl-lysine residue acts as a flexible arm that shuttles the acetyl group from the pyruvate dehydrogenase (E1) enzyme to the dihydrolipoyl acetyltransferase (E2) enzyme Signup and view all the answers

What is the primary role of the dihydrolipoamide acetyltransferase (E2) enzyme in the pyruvate dehydrogenase complex?

To transfer the acetyl group from the lipoyl-lysine residue to coenzyme A Signup and view all the answers

How does the lipoyl-lysine residue contribute to the function of the pyruvate dehydrogenase complex?

The lipoyl-lysine residue serves as a flexible arm that shuttles the acetyl group between the enzymes in the complex Signup and view all the answers

What is the primary role of the pyruvate dehydrogenase complex (PDC) in cellular respiration?

Conversion of pyruvate to acetyl-CoA Signup and view all the answers

Which of the following statements accurately describes the regulation of the pyruvate dehydrogenase complex (PDC)?

PDH phosphatase stimulates the complex by removing the phosphate group Signup and view all the answers

What is the primary role of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

To transfer the acetyl group from pyruvate to coenzyme A Signup and view all the answers

Which enzyme in the pyruvate dehydrogenase complex catalyzes the transfer of the acetyl group from the lipoyl-lysine residue to coenzyme A?

Dihydrolipoyl transacetylase (E2) Signup and view all the answers

What is the primary function of the dihydrolipoyl dehydrogenase (E3) enzyme in the pyruvate dehydrogenase complex?

To reoxidize the lipoamide cofactor using FAD Signup and view all the answers

Which of the following statements accurately describes the role of the lipoyl-lysine residue in the transfer of the acetyl group to coenzyme A?

The lipoyl-lysine residue first transfers the acetyl group to dihydrolipoyl transacetylase (E2), which then transfers it to coenzyme A Signup and view all the answers

How is the pyruvate dehydrogenase complex regulated?

Through phosphorylation by PDH kinase Signup and view all the answers

Pyruvate is converted into which compound by the pyruvate dehydrogenase complex, as stated in the text?

Acetyl CoA Signup and view all the answers

What role does PDH kinase play in relation to the pyruvate dehydrogenase complex based on the text?

Inhibiting the complex by phosphorylation Signup and view all the answers

What molecules are generated for each cycle involving two pyruvate molecules in the pyruvate dehydrogenase complex?

2 CO2, 2 acetyl coa, 2 FADH2, and 2 NADH Signup and view all the answers

What is the role of pyruvate dehydrogenase kinase in the regulation of the pyruvate dehydrogenase complex?

Inhibits enzyme activity Signup and view all the answers

Which molecules can influence the activity of the pyruvate dehydrogenase complex, other than ATP and NADH?

Calcium ions and insulin Signup and view all the answers

Lecture 20

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Questions and Answers

Where does the citric acid cycle occur in eukaryotes?

Which of the following leads to the production of Acetyl CoA?

What is the main role of the pyruvate dehydrogenase complex (PDH) in cellular respiration?

In which stage of cellular respiration does the conversion of pyruvate to Acetyl CoA occur?

Which statement about the respiratory chain in oxidative phosphorylation is correct?

What drives the production of ATP in oxidative phosphorylation?

What is responsible for the reduction of the alkane to alkene in the Electron Transport Chain?

Which enzyme catalyzes the hydration of fumarate to malate?

What type of bond does fumarase always create during the hydration of fumarate to malate?

Which of the following is NOT a reason why intermediates react quickly in the Citrate Synthase and Malate DHase metabolon?

Which of the following statements about the citric acid cycle is NOT true?

In which step(s) of the citric acid cycle is energy conserved by electron transfer to FAD or NAD+, forming FADH2 or NADH + H+?

Which of the following statements about the reversibility of steps in the citric acid cycle is true?

Which of the following statements about the product of step 5 in the citric acid cycle is true?

What is the main similarity between the reaction converting α-ketoglutarate to succinyl-CoA and the pyruvate dehydrogenase reaction?

Which complex is similar in structure and function to the pyruvate dehydrogenase complex?

What is a key feature of the oxidative decarboxylation process catalyzed by the α-Ketoglutarate dehydrogenase complex?

Which statement accurately describes succinyl-CoA?

What role does product inhibition play in the regulation of the α-Ketoglutarate dehydrogenase complex?

What is the purpose of the oxidative decarboxylation reaction catalyzed by isocitrate dehydrogenase?

What is the purpose of the aconitase enzyme in the citric acid cycle?

Which statement is true about the carbon atoms lost as CO2 during the oxidative decarboxylation of isocitrate?

What is the primary function of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

Which of the following statements accurately describes the role of the lipoyl-lysine residue in the transfer of the acetyl group to coenzyme A?

Which of the following statements accurately describes the role of the lipoyl-lysine residue in the oxidation-reduction reactions of the pyruvate dehydrogenase complex?

What is the purpose of the long, flexible arms formed by cofactors like lipoate, biotin, and the combination of β-mercaptoethylamine and pantothenate?

How does the lipoyllysyl moiety contribute to the pyruvate dehydrogenase complex?

In the pyruvate decarboxylation process, what is the role of the dihydrolipoyl transacetylase enzyme?

What is the significance of the oxidized form of the lipoyl residue in accepting the acetyl group?

How does the lipoyl group act as a carrier during the pyruvate decarboxylation process?

What is the primary role of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

What is the role of FAD in the reoxidation of the lipoamide cofactor in the pyruvate dehydrogenase complex?

What is the primary role of the dihydrolipoyl dehydrogenase (E3) enzyme in the pyruvate dehydrogenase complex?

What is the role of thiamine pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

What is the primary role of the dihydrolipoyl transacetylase (E2) enzyme in the pyruvate dehydrogenase complex?

In the pyruvate dehydrogenase complex, which enzyme is responsible for the decarboxylation of pyruvate?

What is the role of the lipoyl-lysine residue in the pyruvate dehydrogenase complex?

What is the function of dihydrolipoyl dehydrogenase (E3) in the pyruvate dehydrogenase complex?

What is the role of thiamine pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

Which enzyme in the pyruvate dehydrogenase complex catalyzes the transfer of the acetyl group from the lipoyl-lysine residue to coenzyme A?

What is the primary role of the dihydrolipoyl dehydrogenase (E3) enzyme in the pyruvate dehydrogenase complex?

What is the primary function of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

What is the role of thiamine pyrophosphate (TPP) in the pyruvate dehydrogenase complex?

What is the main similarity between the reaction converting α-ketoglutarate to succinyl-CoA and the pyruvate dehydrogenase reaction?

What is the role of the lipoyl-lysine residue in the transfer of the acetyl group to Coenzyme A?

What is the primary role of the dihydrolipoamide acetyltransferase (E2) enzyme in the pyruvate dehydrogenase complex?

How does the lipoyl-lysine residue contribute to the function of the pyruvate dehydrogenase complex?

What is the primary role of the pyruvate dehydrogenase complex (PDC) in cellular respiration?

Which of the following statements accurately describes the regulation of the pyruvate dehydrogenase complex (PDC)?

What is the primary role of the lipoyl-lysine residue in the pyruvate dehydrogenase complex (PDC)?

Which enzyme in the pyruvate dehydrogenase complex catalyzes the transfer of the acetyl group from the lipoyl-lysine residue to coenzyme A?

What is the primary function of the dihydrolipoyl dehydrogenase (E3) enzyme in the pyruvate dehydrogenase complex?

Which of the following statements accurately describes the role of the lipoyl-lysine residue in the transfer of the acetyl group to coenzyme A?

How is the pyruvate dehydrogenase complex regulated?

Pyruvate is converted into which compound by the pyruvate dehydrogenase complex, as stated in the text?

What role does PDH kinase play in relation to the pyruvate dehydrogenase complex based on the text?

What molecules are generated for each cycle involving two pyruvate molecules in the pyruvate dehydrogenase complex?

What is the role of pyruvate dehydrogenase kinase in the regulation of the pyruvate dehydrogenase complex?

Which molecules can influence the activity of the pyruvate dehydrogenase complex, other than ATP and NADH?

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