Question 1

In linked metabolic pathways, the oxidants in subsequent reactions must

Accepted Answer

A)  result in negative $\Delta$E$\degree$'  values at each reaction step. 
B)  result in positive $\Delta$G$\degree$'  values at each reaction step. 
C)  have progressively lower standard reduction potentials. 
D)  have progressively higher standard reduction potentials. 
A)  result in negative $\Delta$E$\degree$'  values at each reaction step. 
B)  result in positive $\Delta$G$\degree$'  values at each reaction step. 
C)  have progressively lower standard reduction potentials. 
D)  have progressively higher standard reduction potentials.

Question 2

Identify the strongest oxidant in the table below.

Accepted Answer

A)  O2 
B)  oxaloacetate 
C)  pyruvate 
D)  ferredoxin 
A)  O2 
B)  oxaloacetate 
C)  pyruvate 
D)  ferredoxin

Question 3

Explain how arsenic affects the pyruvate dehydrogenase reaction.

Accepted Answer

Arsenite covalently modifies lipoamide c

Question 4

The $\Delta$G$\degree$ '  of the conversion from malate to oxaloacetate in the last reaction of the citrate cycle is very large, indicating this reaction is not thermodynamically favorable. Propose an explanation for how this reaction can proceed in the forward direction despite the very positive $\Delta$G$\degree$'  value.

Accepted Answer

The oxaloacetate concentrations are kept

Question 5

Which enzyme in the citrate cycle is activated by CoA?

Accepted Answer

A)  "pyruvate dehydrogenase" 
B)  "citrate synthase" 
C)  "isocitrate dehydrogenase" 
D)  "$\alpha$-ketoglutarate dehydrogenase" 
A)  "pyruvate dehydrogenase" 
B)  "citrate synthase" 
C)  "isocitrate dehydrogenase" 
D)  "$\alpha$-ketoglutarate dehydrogenase"

Question 6

Identify the E2 subunit in the reaction schematic of the pyruvate dehydrogenase reaction below.

Accepted Answer

A)  pyruvate dehydrogenase 
B)  dihydrolipoyl dehydrogenase 
C)  dihydrolipopyl acetyltransferase 
D)  flavin adenine dinucleotide 
A)  pyruvate dehydrogenase 
B)  dihydrolipoyl dehydrogenase 
C)  dihydrolipopyl acetyltransferase 
D)  flavin adenine dinucleotide

Question 7

Compare the two roles of lipoic acid in the pyruvate dehydrogenase reaction.

Accepted Answer

Lipoic acid provides a reactiv

Question 8

In the following figure, identify and explain the specific pathways (A-F) that are shared with the citrate cycle intermediates.

Accepted Answer

A. Succinyl-CoA and glycine synthesize @#LAT-DLM&

Question 9

The reaction catalyzed by __________is the most endergonic reaction in the citrate cycle.

Accepted Answer

A)  fumarase 
B)  succinate dehydrogenase 
C)  malate dehydrogenase 
D)  aconitase 
A)  fumarase 
B)  succinate dehydrogenase 
C)  malate dehydrogenase 
D)  aconitase

Question 10

A low NADH to NAD+ ratio would activate which enzyme in the citrate cycle?

Accepted Answer

A)  succinyl-CoA synthetase 
B)  fumarase 
C)  citrate synthase 
D)  succinate dehydrogenase 
A)  succinyl-CoA synthetase 
B)  fumarase 
C)  citrate synthase 
D)  succinate dehydrogenase

Question 11

Which citrate cycle metabolite is used as a precursor for heme biosynthesis?

Accepted Answer

A)  "succinyl Co-A" 
B)  "oxaloacetate" 
C)  "$\alpha$-ketoglutarate" 
D)  "malate" 
A)  "succinyl Co-A" 
B)  "oxaloacetate" 
C)  "$\alpha$-ketoglutarate" 
D)  "malate"

Question 12

In the citrate cycle, a high concentration of NADH would result in

Accepted Answer

A)  activation of citrate synthase. 
B)  inhibition of $\alpha$-ketoglutarate dehydrogenase. 
C)  inhibition of fumarase. 
D)  activation of $\alpha$-ketoglutarate dehydrogenase. 
A)  activation of citrate synthase. 
B)  inhibition of $\alpha$-ketoglutarate dehydrogenase. 
C)  inhibition of fumarase. 
D)  activation of $\alpha$-ketoglutarate dehydrogenase.

Question 13

Where do citrate cycle reactions in eukaryotic cells take place?

Accepted Answer

A)  cytosol 
B)  mitochondrial matrix 
C)  endoplasmic reticulum 
D)  nucleus 
A)  cytosol 
B)  mitochondrial matrix 
C)  endoplasmic reticulum 
D)  nucleus

Question 14

Predict what happens to citrate in a cell when ATP and NADH concentrations are high.

Accepted Answer

The citrate cycle is inhibited under the

Question 15

Explain why riboflavin is critical to the citrate cycle.

Accepted Answer

Riboflavin is the precursor to flavin ad

Question 16

An in vitro study shows that $\alpha$-ketoglutarate dehydrogenase is inhibited in the citrate cycle. What is a possible explanation for this inhibition?

Accepted Answer

A)  high levels of ATP 
B)  low levels of Ca2+ 
C)  low levels of NADH 
D)  high levels of ADP 
A)  high levels of ATP 
B)  low levels of Ca2+ 
C)  low levels of NADH 
D)  high levels of ADP

Question 17

Briefly describe the eight reactions from the citrate cycle, including the identity of the organic reactions and the energetic products.

Accepted Answer

In the first reaction, oxaloacetate unde

Question 18

Classify the reaction that occurs at step 4 in the reaction schematic of the pyruvate dehydrogenase reaction below.

Accepted Answer

A)  isomerization 
B)  addition 
C)  oxidation reduction 
D)  decarboxylation 
A)  isomerization 
B)  addition 
C)  oxidation reduction 
D)  decarboxylation

Question 19

Which enzyme requires CoASH to produce acetyl-CoA?

Accepted Answer

A)  "pyruvate dehydrogenase" 
B)  "citrate synthase" 
C)  "isocitrate dehydrogenase" 
D)  "$\alpha$-ketoglutarate dehydrogenase" 
A)  "pyruvate dehydrogenase" 
B)  "citrate synthase" 
C)  "isocitrate dehydrogenase" 
D)  "$\alpha$-ketoglutarate dehydrogenase"

Question 20

Which citrate cycle intermediate is also used in gluconeogenesis?

Accepted Answer

A)  "oxaloacetate" 
B)  "$\alpha$-ketoglutarate" 
C)  "fumarate" 
D)  "succinate" 
A)  "oxaloacetate" 
B)  "$\alpha$-ketoglutarate" 
C)  "fumarate" 
D)  "succinate"

Exam 10: The Citrate Cycle

In linked metabolic pathways, the oxidants in subsequent reactions must

Identify the strongest oxidant in the table below.

Explain how arsenic affects the pyruvate dehydrogenase reaction.

Which enzyme in the citrate cycle is activated by CoA?

Identify the E2 subunit in the reaction schematic of the pyruvate dehydrogenase reaction below.

Compare the two roles of lipoic acid in the pyruvate dehydrogenase reaction.

In the following figure, identify and explain the specific pathways (A-F) that are shared with the citrate cycle intermediates.

The reaction catalyzed by __________is the most endergonic reaction in the citrate cycle.

A low NADH to NAD+ ratio would activate which enzyme in the citrate cycle?

Which citrate cycle metabolite is used as a precursor for heme biosynthesis?

In the citrate cycle, a high concentration of NADH would result in

Where do citrate cycle reactions in eukaryotic cells take place?

Predict what happens to citrate in a cell when ATP and NADH concentrations are high.

Explain why riboflavin is critical to the citrate cycle.

An in vitro study shows that α\alphaα -ketoglutarate dehydrogenase is inhibited in the citrate cycle. What is a possible explanation for this inhibition?

Briefly describe the eight reactions from the citrate cycle, including the identity of the organic reactions and the energetic products.

Classify the reaction that occurs at step 4 in the reaction schematic of the pyruvate dehydrogenase reaction below.

Which enzyme requires CoASH to produce acetyl-CoA?

Which citrate cycle intermediate is also used in gluconeogenesis?

Principles of Biochemistry

Physical Biochemistry: Energy Conversion, Water, and Membranes

Nucleic Acid Structure and Function

Protein Structure

Methods in Protein Biochemistry

Protein Function

Enzyme Mechanisms

Cell Signaling Systems

Glycolysis: a Paradigm of Metabolic Regulation

Oxidative Phosphorylation

Photosynthesis

Carbohydrate Structure and Function

Carbohydrate Metabolism

Lipid Structure and Function

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Metabolic Integration

DNA Replication, Repair, and Recombination

RNA Synthesis, Processing, and Gene Silencing

Protein Synthesis, Posttranslational Modification, and Transport

Gene Regulation

Filters

A low NADH to NAD⁺ratio would activate which enzyme in the citrate cycle?

An in vitro study shows that $\alpha$ -ketoglutarate dehydrogenase is inhibited in the citrate cycle. What is a possible explanation for this inhibition?