What are the reactants and products of the Krebs Cycle? The Krebs Cycle, also known as the citric acid cycle or the tricarboxylic acid cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is an essential part of cellular respiration, which is the process by which cells generate energy. The reactants of the Krebs Cycle are acetyl-CoA, which is derived from the breakdown of carbohydrates, fats, and proteins, and oxaloacetate, a four-carbon compound. These reactants combine to form citrate, a six-carbon compound. During the Krebs Cycle, citrate undergoes a series of reactions that result in the production of energy-rich molecules such as ATP, NADH, and FADH2. These molecules carry electrons to the electron transport chain, where they are used to generate ATP through oxidative phosphorylation. In addition to ATP, NADH, and FADH2, the Krebs Cycle also produces carbon dioxide as a waste product. This carbon dioxide is released into the bloodstream and eventually exhaled. Overall, the Krebs Cycle plays a crucial role in the production of ATP, which is the primary source of energy for cells. It is an intricate process that involves the conversion of reactants into products through a series of enzymatic reactions.
The Correct Answer and Explanation is:
The Krebs Cycle (also known as the citric acid cycle or tricarboxylic acid cycle) is a crucial metabolic pathway in cellular respiration. It takes place in the mitochondria of cells and is responsible for generating energy-rich molecules that are used to produce ATP, the primary energy carrier in cells.
Reactants:
- Acetyl-CoA: This molecule is derived from the breakdown of carbohydrates, fats, and proteins. During glycolysis, glucose is broken down into pyruvate, which is then converted into Acetyl-CoA in the mitochondria.
- Oxaloacetate: A four-carbon compound that is regenerated during the cycle. Oxaloacetate combines with acetyl-CoA to form citrate at the beginning of the cycle.
Products:
- Citrate: A six-carbon compound formed when Acetyl-CoA combines with oxaloacetate. This is the first molecule of the cycle.
- NADH: This molecule is a key electron carrier. During the Krebs Cycle, NAD+ is reduced to NADH when it accepts electrons and hydrogen ions.
- FADH2: Another electron carrier, similar to NADH. FAD is reduced to FADH2 in the cycle.
- ATP: A small amount of ATP is directly produced through substrate-level phosphorylation in the Krebs Cycle.
- Carbon Dioxide (CO2): Two molecules of CO2 are produced as waste products during the cycle. These are exhaled by the organism.
Explanation:
The Krebs Cycle begins when acetyl-CoA enters the cycle and combines with oxaloacetate to form citrate, a six-carbon molecule. Through a series of enzyme-catalyzed reactions, citrate undergoes decarboxylation (removal of CO2) and oxidation (loss of electrons). These steps lead to the production of high-energy molecules like NADH and FADH2. Additionally, one molecule of ATP is generated in the process. The cycle continues as oxaloacetate is regenerated, allowing the process to repeat.
The NADH and FADH2 produced in the Krebs Cycle are essential for the subsequent stage of cellular respiration, the electron transport chain, where they are used to produce a large amount of ATP through oxidative phosphorylation. Thus, the Krebs Cycle plays an integral role in energy production and metabolism within the cell.
