Citric Acid Cycle Flashcards
How many reactions are there in the CA cycle?
8
List the reactions of the CA cycle in order
1) Acetyl CoA –> Citrate (6)
2) Citrate –> isocitrate (6)
3) isocitrate –> a-ketoglutarate (5)
4) a-ketoglutarate –> succinyl CoA (4)
5) succinyl CoA –> Succinate (4)
6) succinate –> fumarate (4)
7) fumarate –> malate (4)
8) malate –> oxaloacetate (4)
name the enzyme that catalyses each step of the CA cycle
1) Citrate synthase
2) aconitase
3) isocitrate dehydrogenase
4) a-ketoglutarate dehydrogenase
5) succinyl CoA synthetase
6) succinate dehydrogenase
7) fumarase
8) malate dehydrogenase
Which steps of the CA cycle produce NADH, FADH2, GTP and/or CO2?
NADH = steps 3, 4, and 8 FADH2 = step 6 CO2 = steps 3 and 4 GTP = step 5
Which enzyme has an analogous structure and sequence of reactions to Pyruvate dehydrogenase?
a-ketoglutarate dehydrogenase
a-ketoglutarate + CoA + NAD+ —> Succinyl CoA + CO2 + NADH
What is the maximum number of ATP molecules that can produced by the oxidative phosphorylation of one glucose molecule?
38
Which enzymes are the key regulatory steps for CA cycle?
a-ketoglutarate dehydrogenase
isocitrate dehydrogenase
How is a-ketoglutarate dehydrogenase regulated?
Allosteric regulation:
- binding of ATP, Succinyl CoA, NADH = inhibits
- binding of calcium = activates
How is isocitrate dehydrogenase regulated?
Allosteric regulation:
- binding of ATP and NADH = inhibits
- binding of ADP = activates
What are the biosynthetic intermediates of the citric acid cycle?
Oxaloacetate = aspartate = other amino acids, purines, pyrimidines
Citrate = fatty acids, sterols
a-ketoglutarate = glutamate = other amino acids, purines
Succinyl CoA = porphyrins, haem, chlorophyll
Which enzyme of the citric acid cycle is also part of the respiratory chain?
Succinate dehydrogenase
- produces FADH2 which is used to reduce ubiquinone in the membrane pool
