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Questions and Answers
What is the primary product of Acetyl-CoA oxidation in the TCA cycle?
What is the primary product of Acetyl-CoA oxidation in the TCA cycle?
Which of the following compounds is produced from α-ketoglutarate through transamination?
Which of the following compounds is produced from α-ketoglutarate through transamination?
Which coenzyme is NOT utilized by the pyruvate dehydrogenase complex?
Which coenzyme is NOT utilized by the pyruvate dehydrogenase complex?
What inhibits the regulatory enzymes of the TCA cycle?
What inhibits the regulatory enzymes of the TCA cycle?
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Which substance inhibits aconitase in the Krebs cycle?
Which substance inhibits aconitase in the Krebs cycle?
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What is the primary role of the pyruvate dehydrogenase enzyme complex in the metabolic pathway?
What is the primary role of the pyruvate dehydrogenase enzyme complex in the metabolic pathway?
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Which of the following coenzymes is NOT utilized by the pyruvate dehydrogenase complex?
Which of the following coenzymes is NOT utilized by the pyruvate dehydrogenase complex?
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How many ATP molecules are generated from the two NADHH produced during the oxidative decarboxylation of one glucose molecule?
How many ATP molecules are generated from the two NADHH produced during the oxidative decarboxylation of one glucose molecule?
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What is the primary end product of the Krebs' cycle?
What is the primary end product of the Krebs' cycle?
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Which of the following accurately describes the relationship between the Krebs' cycle and the oxidative phosphorylation process?
Which of the following accurately describes the relationship between the Krebs' cycle and the oxidative phosphorylation process?
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What happens to the hydrogen generated by the coenzymes in the Krebs' cycle?
What happens to the hydrogen generated by the coenzymes in the Krebs' cycle?
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Which metabolic substrates can be completely oxidized in the Krebs' cycle?
Which metabolic substrates can be completely oxidized in the Krebs' cycle?
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During the conversion of pyruvate to acetyl-CoA, what is produced alongside acetyl-CoA?
During the conversion of pyruvate to acetyl-CoA, what is produced alongside acetyl-CoA?
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Study Notes
Aerobic Oxidation of Glucose
- Glucose is oxidized aerobically, a process vital for energy production.
- Pyruvate, a product of glycolysis, is further oxidatively decarboxylated to Acetyl-CoA in the mitochondria.
- This conversion is catalyzed by the pyruvate dehydrogenase enzyme complex.
Krebs' Cycle (Citric Acid Cycle, Tricarboxylic Acid Cycle)
- This is a crucial cycle for complete oxidation of Acetyl-CoA, derived from carbohydrates, fats, and amino acids.
- The cycle produces CO2, FADH2, and NADH.
- Hydrogen from the coenzymes (NADH, FADH2) is used in the electron transport chain.
- The Krebs Cycle is a common pathway for oxidation of carbohydrates, lipids, and proteins.
- The cycle's name honors Hans Adolf Krebs, who discovered it in 1937.
Pyruvate Dehydrogenase
- The Pyruvate Dehydrogenase utilizes five coenzymes (TPP, CoASH, Lipoic Acid, FAD, and NAD).
- It's a multi-enzyme complex catalyzing the oxidation of pyruvate to Acetyl-CoA.
- The complete reaction involves the removal of hydrogen and CO2 from pyruvate.
- This multienzyme complex involves 3-step reactions - Decarboxylation - Hydride Transfer - Thioester Formation
- The NADH produced during this process proceeds to the ETC giving 2.5 ATP.
Krebs' Cycle Steps
- Pyruvate is transported into mitochondria.
- Oxidative decarboxylation of pyruvate. - Pyruvate releases hydrogen and CO2 to create Acetyl CoA & NADH
Regulation of Pyruvate Dehydrogenase
- Regulation of Pyruvate Dehydrogenase Complex is controlled by activity of ADP and ATP
- Active form (Dephospho-form) is stimulated by insulin (during Fed state).
- Inactive form (Phospho-form) is stimulated by glucagon & adrenaline (during Fasting state).
- ATP inhibits, while ADP stimulates the key regulatory enzymes in the TCA cycle.
Regulation of TCA Cycle
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Three key regulatory enzymes are:
- Citrate synthase
- Isocitrate dehydrogenase
- α-ketoglutarate dehydrogenase
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Allosteric regulation is a common mechanism that regulates the cycle's speed by controlling the activity of the enzymes.
Importance of Krebs' Cycle
- Crucial for energy production, oxidizing acetyl-CoA to CO2 and H2O.
- Provides substrates (e.g., succinyl CoA) for porphyrin and nonessential amino acid synthesis.
In Vitro Inhibitors of Krebs' Cycle
- Fluoroacetate: Inhibits the aconitase enzyme.
- Arsenate: Inhibits α-ketoglutarate dehydrogenases.
- Malonate: Inhibits succinate dehydrogenase enzyme.
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Description
This quiz covers the aerobic oxidation of glucose and the Krebs cycle, crucial processes in cellular respiration. It explores the conversion of pyruvate to Acetyl-CoA, the enzymatic roles, and the cycle's significance in energy production. Test your knowledge of these metabolic pathways and their importance in biochemistry.
