what are the reactants of the krebs cycle?
The Correct Answer and Explanation is:
Correct Answer:
The main reactants of the Krebs cycle are acetyl-CoA, NAD⁺, FAD, ADP (or GDP), and inorganic phosphate (Pi). Additionally, oxaloacetate is required to combine with acetyl-CoA and initiate the cycle.
Explanation:
The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a central part of cellular respiration. This metabolic pathway takes place in the mitochondrial matrix and plays a key role in energy production. The primary purpose of the Krebs cycle is to extract high-energy electrons from carbon fuels to be used in the electron transport chain, where ATP is ultimately produced.
The cycle begins when acetyl-CoA, a two-carbon molecule derived from carbohydrates, fats, or proteins, combines with oxaloacetate, a four-carbon molecule. This combination forms citrate, a six-carbon molecule. Oxaloacetate acts as a starting molecule that is regenerated at the end of the cycle, enabling the cycle to continue as long as acetyl-CoA is available.
During the cycle, several reactions occur that remove carbon atoms in the form of carbon dioxide. These decarboxylation steps are accompanied by the reduction of electron carriers. Three molecules of NAD⁺ are reduced to NADH, and one molecule of FAD is reduced to FADH₂ per turn of the cycle. These reduced coenzymes carry high-energy electrons to the electron transport chain.
In addition to the reduced coenzymes, one molecule of GTP (or sometimes ATP, depending on the cell type) is synthesized through substrate-level phosphorylation. An inorganic phosphate and GDP (or ADP) are required for this step.
Thus, the essential reactants that fuel the Krebs cycle are acetyl-CoA, oxaloacetate, NAD⁺, FAD, GDP (or ADP), and Pi. Without these inputs, the cycle would not operate efficiently, and the cell would not be able to generate the electron carriers necessary for oxidative phosphorylation and ATP production.
