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Overview of Citric Acid Cycle
| Content Provider | AK Lectures |
|---|---|
| Description | The citric acid cycle consists of eight steps. Step 1 is the formation of citrate from oxaloacetate and acetyl-CoA by the action of citrate synthase. This step is exergonic and releases about -31.4 kJ/mol of energy. In step 2, the citrate is converted into an isomer molecule called isocitrate by the action of aconitase. This step is endergonic and requires an input of about 6.3 kJ/mol of energy. This conversion helps prepare the molecule for the first decarboxylation step. In step 3, isocitrate undergoes an oxidative decarboxylation reaction in which the enzyme isocitrate dehydrogenase creates alpha-ketoglutarate. This produces an NADH molecule and releases a carbon dioxide. Step 4 is also an oxidative decarboxylation step that is catalyzed by a different enzyme called the alpha-ketolgutarate dehydrogenase complex. This step produces succinyl CoA, generates another NADH molecule and releases a carbon dioxide. In step 5, succinyl CoA synthetase transforms the succinyl CoA into a succinate; in the process, a GDP molecule is transformed into a GTP. In step 6, the succinate is transformed into a fumarate by the action of succinyl dehydrogenase, an enzyme that is bound to the inner mitochondrial membrane. In step 7, fumarate is transformed into the L-isomer of malate via a hydration reaction and by the action of the enzyme fumarase. In the final step of the citric acid cycle, the fumarate is converted into oxaloacete by malate dehydrogenase. This forms yet another NADH molecule. In total, a single acetyl CoA that moves into the citric acid cycle produces three NADH molecules, a single FADH2 molecule and a single GTP. |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Biochemistry succinate L-isomer process GTP malate moves oxaloacete acetyl-CoA forms acid cycle |
| Content Type | Video |
| Educational Role | Teacher Student |
| Educational Use | Self Learning Lecture Reading |
| Resource Type | Video Lecture |
| Education Level | Under Graduate |
| Subject | Biochemistry |
