Citric Acid Cycle Flashcards
Where does the TCA cycle occur?
Mitochondrial matrix
Which of the compounds below are the products of the oxidation of acetyl CoA in the citric acid cycle?
A. Oxaloacetate and NAD
B. GTP and Acetyl CoA
C. NADH, FADH2 and CO2
D. Water, CO2 and ATP
C
How many high-energy phosphates (ATP) can be obtained from the over-all reaction:
Isocitrate — > —– > —— > Fumarate + 2CO2 + 2 H2O
A. 7
B. 8
C. 9
D. 10
C
Which is true of TCA cycle?
a. It produces reducing equivalents for\ETC
b. Has anabolic and catabolic phases
c. It is the final common pathway for the metabolism of glucose, fatty acid and amino acids
d. All of the above
D
Before pyruvate can enter the TCA, it must be converted to acetyl acid. Which enzyme catalyzes this reaction?
Pyruvate dehydrogenase
Pyruvate dehydrogenase required five coenzymes. Which are they?
TPP, FAD, CoA, NAD, lipoate
Which molecules undergo condensation to form citrate?
Oxaloacetate and acetyl CoA
Which enzyme catalyzes the formation of citrate?
Citrate synthase
Which enzyme catalzes the conversion of isocitrate to α-ketoglutarate?
Isocitrate dehydrogenase
Which enzyme catalyzes conversion of α -ketoglutarate to succinyl-CoA?
α -ketoglutarate dehydrogenase
Which enzymes of the TCA produce carbon dioxide?
Isocitrate dehydrogenase and α -ketoglutarate dehydrogenase
Which enzymes need NAD+ as electron acceptor?
Isocitrate dehydrogenase, α -ketoglutarate dehydrogenase and L-malate dehydrogenase
Which enzyme of the TCA closely resembles the PDH complex in both structure and function?
α -ketoglutarate dehydrogenase
Which cofactors does α -ketoglutarate dehydrogenase require?
NAD, FAD, TPP, lipoate, CoA
PDH complex and α -ketoglutarate dehydrogenase complex are each made up of how many enzymes?
3
Which enzyme catalyzes the conversion of succinyl-CoA to succinate?
Succinyl-CoA synthetase/ succinic thiokinase
Which enzyme catalyzes the conversion of succinate to fumarate?
Succinate dehydrogenase
Which enzyme of the TCA produces GTP /ATP?
Succinyl-CoA synthetase/ succinic thiokinase
Which enzyme of the TCA produces FADH2?
Succinate dehydrogenase
Which enzyme catalyzes the hydration of fumarate to malate?
Fumarase
Which enzyme catalyzes the dehydration of malate to oxaloacetate?
L-malate dehydrogenase
What are the products of TCA?
3 NADH, 1 FADH2, 2CO2, 1 ATP (GTP)
Oxaloacetate has an extremely low concentration in the cell. T/F
T
Citric acid cycle is an amphibolic pathway. What does it mean?
The citric acid cycle serves both catabolic and anabolic processes
When the citric acid cycle is deficient in oxaloacetate or any other intermediates, how does the cell produce these intermediates?
Pyruvate is carboxylated to oxaloacetate
Pyruvate carboxylase is inactive without which positive allosteric modulator?
Acetyl-CoA
PEP is activated by F 1,6-BP. T/F
T
Biotin is a specialized carrier of one-carbon groups in their most oxidized form; CO2. T/F
T
Succinyl-CoA inhibits which TCA enzymes?
α -ketoglutarate dehydrogenase and citrate synthase
Citrate is an allosteric inhibitor of which glycolytic enzyme?
PFK-1
