8 steps of krebs cycle

what occurs during the preparatory step prior to the TCA cycle?

the conversion of pyruvate into acetyl CoA. the pyruvate will produced leading to 2 pyruvate (1 glucose = 2 pyruvate). the reaction is catalyzed by pyruvate dehydrogenase, producing 2 NADH and releasing CO2

what occurs during step 1 of the TCA cycle?

oxaloacetate reacts with acetyl CoA to form citrate, the reaction being catalyzed by enzyme citrate synthase. it is considered irreversible and a rate limiting step. it is a condensation reaction

what occurs during step 2 of the TCA cycle?

citrate will be catalyzed by enzyme aconitase to form isocitrate, known as a reversible isomerization step.

what occurs during step 3 of the TCA cycle?

isocitrate will be catalyzed by isocitrate dehydrogenase to form α-ketoglutarate, producing 1 NADH and releasing 1 CO2 in the process. it is considered an irreversible and rate-limiting step, and is the primary regulatory step of the Krebs cycle

what occurs during step 4 of the TCA cycle?

α-ketoglutarate is catalyzed by enzyme α-ketoglutarate dehydrogenase to form succinyl-CoA, producing 1 NADH and releasing 1 CO2 in the process. it is an irreversible and rate-limiting step, and is considered an additional regulatory step of the TCA cycle

what occurs during step 5 of the TCA cycle?

succinyl-CoA is catalyzed by succinyl-CoA-synthase to form succinate, producing one GTP or ATP in the process and has substrate level phosphorylation

what occurs during step 6 of the TCA cycle?

succinate is catalyzed by succinate dehydrogenase to form fumarate, producing one FADH2 in the process. it is known as the oxidation step

what occurs during step 7 of the TCA cycle?

fumarate is catalyzed by fumarase to form malate, and it is known as the hydration reaction

what occurs during step 8 of the TCA cycle?

malate is catalyzed by malate dehydrogenase to form oxaloacetate, producing 1 NADH in the process. it is the last step of the cycle, regenerating OAA so it can renter the cycle.

what are the irreversible and rate-limiting steps?

• step 1 (citrate synthase)

• step 3 (isocitrate dehydrogenase)

• step 4 (α-ketoglutarate dehydrogenase)

what are the regulatory enzymes of the TCA cycle?

• isocitrate dehydrogenase (step 3)

• α-ketoglutarate dehydrogenase (step 4)

what is the main regulatory enzyme of the TCA cycle?

isocitrate dehydrogenase (step 3)

what steps is CO2 released?

steps 3 and 4, which are isocitrate dehydrogenase and α-ketoglutarate

what are the energy producing steps?

• step 3, 1 NADH is produced (isocitrate dehydrogenase)

• step 4, 1 NADH is produced (α-ketoglutarate dehydrogenase)

• step 5, 1 GTP is produced (succinyl-CoA-synthase)

• step 6, 1 FADH2 is produced (succinate dehydrogenase)

• step 8, 1 NADH is produced (malate dehydrogenase)

total ATP produced based on 1 cycle is?

3 NADH x 3 = 9 ATP, 1 FADH2 × 2 = 2 ATP, 1 GTP = 1 ATP, 9 + 2 + 1 = 12 ATP