Citric Acid Cycle

Citric acid cycle enzymes and products

Before the citric acid cycle begins, pyruvate is oxidized to …

acetyl-CoA

The oxidation of pyruvate to acetyl-CoA is catalyzed by …

pyruvate dehydrogenase

Reaction 1: Acetyl-CoA attacks […] to form […]

oxaloacetate; citrate

The formation of citrate is catalyzed by …

citrate synthase

In the formation of citrate, […] is released

coenzyme A

Reaction 2: Citrate is isomerized to …

isocitrate

The isomerization of citrate is catalyzed by …

aconitase

Reaction 3: isocitrate is oxidatively decarboxylated to …

α-ketoglutarate

The oxidation of isocitrate is catalyzed by […] and generates […]

isocitrate dehydrogenase; 1 NADH

Reaction 4: α-Ketoglutarate is oxidatively decarboxylated to …

succinyl-CoA

The oxidation of α-ketoglutarate is catalyzed by …

α-ketoglutarate dehydrogenase

In the oxidation of α-ketoglutarate, […] is added on to α-ketoglutarate

coenzyme A

In the oxidation of α-ketoglutarate, […] is reduced to […]

NAD⁺; NADH and H⁺

Reaction 5: […] is removed from succinyl-CoA to form […]

coenzyme A; succinate

The formation of succinate is catalyzed by …

succinyl-CoA synthase

The formation of succinate additionally produces one molecule of […], which is used to make […]

GTP; ATP

Reaction 6: Succinate is oxidized to …

fumarate

The oxidation of succinate is catalyzed by …

succinate dehydrogenase

In the oxidation of succinate, […] is reduced to […]

FADH; FADH₂

Reaction 7: Fumarate is reversibly hydrated to …

L-malate

The hydration of fumarate is catalyzed by […], a.k.a. […]

fumarase; fumarate hydratase

Reaction 8: Malate is reversibly oxidized to …

oxaloacetate

The oxidation of malate is catalyzed by …

malate dehydrogenase

In the oxidation of malate, (…) is reduced to (…)

NAD⁺; NADH and H⁺

One rotation of the citric acid cycle yields …*

*total amount of energy producing products

3 NADH, 1 FADH₂, and 1 ATP

What are the overall starting materials of the citric acid cycle?

acetyl-CoA + oxaloacetate + 3 NAD⁺ + GDP + P_i + FAD

What are the overall products of the citric acid cycle?

oxaloacetate + 2 CO₂ + FADH₂ + 3 NADH + 3 H⁺ + GTP