Why does krebs cycle occur in the mitochondria

Step six is a dehydration process that converts succinate into fumarate. Unlike NADH, this carrier remains attached to the enzyme and transfers the electrons to the electron transport chain directly. This process is made possible by the localization of the enzyme catalyzing this step inside the inner membrane of the mitochondrion. Step 7. Water is added to fumarate during step seven, and malate is produced.

The last step in the citric acid cycle regenerates oxaloacetate by oxidizing malate. Another molecule of NADH is produced. Two carbon atoms come into the citric acid cycle from each acetyl group, representing four out of the six carbons of one glucose molecule. Two carbon dioxide molecules are released on each turn of the cycle; however, these do not necessarily contain the most recently-added carbon atoms.

The two acetyl carbon atoms will eventually be released on later turns of the cycle; thus, all six carbon atoms from the original glucose molecule are eventually incorporated into carbon dioxide.

These carriers will connect with the last portion of aerobic respiration to produce ATP molecules. Several of the intermediate compounds in the citric acid cycle can be used in synthesizing non-essential amino acids; therefore, the cycle is amphibolic both catabolic and anabolic. In order for pyruvate, the product of glycolysis, to enter the next pathway, it must undergo several changes to become acetyl Coenzyme A acetyl CoA.

Acetyl CoA is a molecule that is further converted to oxaloacetate, which enters the citric acid cycle Krebs cycle. The conversion of pyruvate to acetyl CoA is a three-step process. Breakdown of Pyruvate : Each pyruvate molecule loses a carboxylic group in the form of carbon dioxide. A carboxyl group is removed from pyruvate, releasing a molecule of carbon dioxide into the surrounding medium.

Note: carbon dioxide is one carbon attached to two oxygen atoms and is one of the major end products of cellular respiration. The result of this step is a two-carbon hydroxyethyl group bound to the enzyme pyruvate dehydrogenase; the lost carbon dioxide is the first of the six carbons from the original glucose molecule to be removed.

This step proceeds twice for every molecule of glucose metabolized remember: there are two pyruvate molecules produced at the end of glycolysis ; thus, two of the six carbons will have been removed at the end of both of these steps.

Step 3. The enzyme-bound acetyl group is transferred to CoA, producing a molecule of acetyl CoA. This molecule of acetyl CoA is then further converted to be used in the next pathway of metabolism, the citric acid cycle. The citric acid cycle is a key component of the metabolic pathway by which all aerobic organisms generate energy.

The citric acid cycle, shown in —also known as the tricarboxylic acid cycle TCA cycle or the Krebs cycle—is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide. The cycle provides precursors including certain amino acids as well as the reducing agent NADH that is used in numerous biochemical reactions.

Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism; it may have originated abiogenically. The Citric Acid Cycle : The citric acid cycle, or Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide.

This page has been archived and is no longer updated. Cell Energy and Cell Functions. Metabolism in a eukaryotic cell: Glycolysis, the citric acid cycle, and oxidative phosphorylation.

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Remember that there are two acetyl-CoA produced from the two pyruvate molecules end product of glycolysis. During glycolysis glucose is the primary reactant.

Glucose contains six carbons. The process of glycolysis converts one molecule of glucose into two molecules of pyruvate with three carbons each. Pyruvate then undergoes a decarboxylation reaction before entering the Krebs cycle. Each pyruvate loses one carbon to create carbon dioxide during this reaction, with the end product of acetyl-CoA. Acetyl-CoA is, thus, a two-carbon chain. The products can then be turned around to continue fueling the Krebs cycle.

Since the ETC will not function in an anaerobic environment, neither will the Krebs cycle. The reactants will not be replenished, and the cycle will be unable to continue.

Oxygen is not directly involved as a reactant or product of the Krebs cycle. Oxygen is only directly used as an electron receptor in the electron transport chain. All of the other selections are products in the citric acid cyclce. Carbon dioxide CO 2 is produced during carbohydrate conversions in the cycle.

An anabolic reaction is one in which larger molecules are made from combining smaller molecules. Even without knowing the exact mechanics of the reactions given in the answer choices, we know that we are looking for a reaction in which multiple molecules combine to form a single molecule.

Out of the options, there is only one time where a larger molecule is made by the combination of two smaller ones: when acetyl CoA 2 carbons and oxaloacetate 4 carbons come together in order to create citrate 6 carbons. The generation of pyruvate from glucose results in two smaller molecules from one larger molecule; this is a catalysis reaction. The conversion of glucosephosphate to fructosephosphate is an isomerization reaction.

The transition from citrate to ketoglutarate is processed through an intermediate, but is ultimately a catalysis reaction. Fermentation is a catabolic process which does not require oxygen. In contrast, Krebs cycle citric acid cycle and oxidative phosphorylation chemiosmosis and electron transport do use oxygen. Aerobic respiration is much more efficient than anaerobic respiration in producing ATP. If you've found an issue with this question, please let us know.

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Subject optional. Email address: Your name:. Example Question 51 : Cellular Respiration. Where does the citric acid cycle take place in eukaryotic cells? Possible Answers: Golgi body. Correct answer: Mitochondria. Explanation : The citric acid cycle, also known as the Kreb's cycle, occurs within the mitochondria of eukaryotic cells. Report an Error. Possible Answers: inner mitochondrial membrane.