what exactly happens in the krebs cycle
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The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid cycle (TCA cycle), is a crucial series of chemical reactions that takes place in the mitochondria of cells. It plays a central role in cellular respiration, the process that generates energy.
To understand what exactly happens in the Krebs cycle, let's break it down step by step:
1. Acetyl-CoA Formation: The cycle starts when pyruvate, a byproduct of glycolysis (the initial step of cellular respiration), enters the mitochondria. Pyruvate is converted into Acetyl-CoA by losing carbon dioxide (CO2). This conversion is catalyzed by an enzyme called pyruvate dehydrogenase.
2. Citrate Formation: Acetyl-CoA then combines with a molecule called oxaloacetate to form citrate. This reaction, catalyzed by the enzyme citrate synthase, marks the beginning of the Krebs cycle.
3. Energy Extraction: During the cycle, citrate undergoes a series of chemical reactions, releasing energy in the form of ATP, NADH, and FADH2. These energy-rich molecules act as carriers, storing the energy temporarily for later use in the electron transport chain (the final step of cellular respiration).
4. Carbon Dioxide Release: As these reactions progress, carbons are gradually removed from the citrate molecule, releasing carbon dioxide as waste. This step generates NADH and FADH2, which carry high-energy electrons to the next stage.
5. Regeneration: At the end of the Krebs cycle, oxaloacetate is regenerated to begin the cycle again. The cycle completes when more Acetyl-CoA enters and combines with the regenerated oxaloacetate.
It is important to note that the Krebs cycle occurs twice for each glucose molecule, as two pyruvate molecules are produced during glycolysis. This means that for each round of the Krebs cycle, two ATP, six NADH, and two FADH2 molecules are produced.
Understanding the detailed steps of the Krebs cycle requires a knowledge of biochemistry and enzymology. It is a complex process that efficiently extracts energy from glucose molecules while producing important molecules for subsequent energy production in the electron transport chain.