Krebs Cycle Flashcards Preview

MCAT biochemistry > Krebs Cycle > Flashcards

Flashcards in Krebs Cycle Deck (10):
1

what part of the cell does Krebs cycle take place?

in the mitochondrial matrix

2

the final products are

6 NADH
2 FADH2
2 ATP

3

reaction 1: citrate
(citrate synthase)

it is a condensation reaction between acetyl-CoA with oxaloacetate to form citrate
citrate synthase enzyme catalyzes the reaction by joining oxalocacetate with acetyl-CoA and then a water molecule attacks the acetyl lead to release coenzyme A from the complex and H+ is released

4

reaction 2: isocitrate
(aconitase)

it is the formation of isocitrate through the rearrangement of citrate
acontinase enzyme is used to remove a water molecule from citrate to be put on another location to yield isocitrate

5

reaction 3: alpha-ketoglutarate
(isocitrate dehydrogenase)

it is the oxidation of isocitrate into alpha-ketoglutarate
isocitrate dehydrogenase enzyme catalyzes the -OH group and hydrogen on C4 to yield an intermediate (oxalosuccinate) which has a generation of NAD+ to NADH + H+ and then loses a CO2 molecule to yield the alpha-ketoglutarate

6

reaction 4: succinyl-CoA
(alpha-ketoglutarate dehydroenase)

it is the oxidation of alpha-ketoglutarate to form succinyl-CoA
alpha-ketoglutarate dehydrogenase enzyme is used to reduced another NAD+ to NADH, have CO2 removed, and have coenzyme A added to form the 4-carbon compound, succinyl-CoA

7

reaction 5: succinate
(succinyl-CoA synthetase)

it is the conversion of succinyl-CoA to produce succinate
succinyl-CoA synthetase enzyme catalyzes the reaction by removing CoA, which allows for energy release to be used to make GTP from GDP + phosphate (Pi) by substrate-level phosphorylation
*GDP is used to make ATP

8

reaction 6: fumarate
(succinate dehydrogenase)

it is the oxidation of succinate into fumarate
succinate dehydrogenase enzyme is used to catalyze the removal of two hydrogens from succinate and for the reduction of FAD to FADH2

9

reaction 7: malate
(fumarase)

it is the hydration (reversible) of fumarate into L-malate
fumarase enzyme catalyzes this reaction by a rearrangement process from adding hydrogen and oxygen back into the substrate that had been previously removed

10

reaction 8: oxaloacetate
(malate dehydrogenase)

it is the oxidation of malate to produce oxaloacetate
malate dehydrogenase enzyme is used to catalyze the process of making the starting product of krebs cycle and also reduced NAD+ to NADH and H+
the new oxaloacetate is used to renter the cycle?