Welcome to our comprehensive guide to the TCA (Tricarboxylic Acid) cycle, a vital component of cellular respiration and energy production within our cells. In this video, we’ll delve deep into the intricacies of this metabolic pathway, breaking down each step to help you grasp the fascinating journey from Acetyl CoA to ATP. Whether you’re a biology student, science enthusiast, or simply curious about the inner workings of your cells, this tutorial is tailored for you.
Credit – The voice was generated from Eleven Labs AI voice
0:00 – 0:23- Introduction to the TCA Cycle
0:27 – Mitochondria
0:38 – Acetyl CoA
0:51 – Citrate Formation
1:05 – Isocitrate Formation
1:44 – Succinyl CoA
02:05 – Succinate Formation
02:30 – Fumarate Formation
02:46 – Malate Formation
03:01 – Oxaloacetate Formation
03:22 – Recap and Conclusion
About The TCA cycle(Krebs cycle):
The TCA (tricarboxylic acid) cycle, also known as the Krebs cycle or citric acid cycle, is a central metabolic pathway that occurs in the mitochondria of eukaryotic cells. It plays a critical role in the production of ATP (adenosine triphosphate), the primary energy currency of cells. The TCA cycle is a series of biochemical reactions that oxidize acetyl-CoA, derived from various fuel sources, to generate reducing equivalents in the form of NADH and FADH2, which are then used in the electron transport chain to produce ATP. Let’s delve into the details of the TCA/Krebs cycle:
1. Entry of Acetyl-CoA: The TCA cycle begins when a two-carbon compound, acetyl-CoA, is introduced into the cycle. Acetyl-CoA is formed from various sources such as the breakdown of glucose, fatty acids, and amino acids. It combines with a four-carbon compound, oxaloacetate, to form citrate, a six-carbon compound.
2. Citrate Isomerization: Citrate undergoes isomerization to isocitrate through the action of the enzyme aconitase. This step does not produce or consume any ATP or reducing equivalents but rearranges the carbon atoms within the molecule.
3. First NADH Production: Isocitrate is then oxidized by isocitrate dehydrogenase, resulting in the release of carbon dioxide (CO2) and the generation of the first NADH molecule. The product of this reaction is alpha-ketoglutarate.
4. Second Decarboxylation: Alpha-ketoglutarate undergoes another decarboxylation reaction catalyzed by alpha-ketoglutarate dehydrogenase complex, which is similar to the pyruvate dehydrogenase complex in glycolysis. This reaction releases another CO2 molecule and generates a second molecule of NADH. The product is succinyl-CoA.
5. Substrate-Level Phosphorylation: Succinyl-CoA is then converted into succinate by the enzyme succinyl-CoA synthetase. During this step, a molecule of GTP (guanosine triphosphate) is generated by substrate-level phosphorylation. GTP can later be converted into ATP.
6. Third NADH Production: Succinate is oxidized to fumarate by succinate dehydrogenase, an enzyme complex embedded in the inner mitochondrial membrane. This reaction also generates the third molecule of NADH.
7. Hydration of Fumarate: Fumarate is converted into malate through the addition of water, a reaction catalyzed by fumarase.
8. Final NADH Production: Malate is then oxidized to regenerate oxaloacetate by malate dehydrogenase, generating the fourth molecule of NADH in the process.
9. Oxaloacetate Regeneration: The cycle is completed when oxaloacetate is regenerated, and it can combine with another molecule of acetyl-CoA to start the cycle anew.
Overall Impact: Energy Production
The TCA cycle serves two primary purposes:
1) To generate energy-rich molecules: Throughout the cycle, NADH and FADH2 are produced, which carry high-energy electrons to the electron transport chain, where ATP (adenosine triphosphate) is synthesized via oxidative phosphorylation.
2) To provide precursor molecules: The TCA cycle also produces intermediates that can be used in other metabolic pathways for the synthesis of amino acids, fatty acids, and other essential molecules.
The TCA cycle is a crucial part of cellular respiration, and its efficient functioning is essential for the production of the energy currency ATP and the maintenance of various metabolic processes in the cell. Understanding this cycle is fundamental in the fields of biology, biochemistry, and physiology, as it underpins many aspects of life and health.
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