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Questions and Answers
What is the role of Coenzyme A in the process described?
What is the role of Coenzyme A in the process described?
What does the lipoamide cofactor primarily accomplish during the enzymatic function?
What does the lipoamide cofactor primarily accomplish during the enzymatic function?
What substance is produced by the Succinyl-CoA synthetase during its reaction?
What substance is produced by the Succinyl-CoA synthetase during its reaction?
What is the final product of the reaction catalyzed by succinate dehydrogenase?
What is the final product of the reaction catalyzed by succinate dehydrogenase?
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How does succinate dehydrogenase connect the citric acid cycle to the electron transport chain?
How does succinate dehydrogenase connect the citric acid cycle to the electron transport chain?
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What type of enzymatic reactions does succinate dehydrogenase perform?
What type of enzymatic reactions does succinate dehydrogenase perform?
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What occurs to the electrons transferred from FADH2 during the reactions described?
What occurs to the electrons transferred from FADH2 during the reactions described?
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What is the primary function of the succinyl group in the context of succinyl-CoA synthetase?
What is the primary function of the succinyl group in the context of succinyl-CoA synthetase?
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What is the starting molecule of the Kreb Cycle?
What is the starting molecule of the Kreb Cycle?
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How many metabolic reactions occur in the Kreb Cycle?
How many metabolic reactions occur in the Kreb Cycle?
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What is the primary function of the Kreb Cycle?
What is the primary function of the Kreb Cycle?
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Which molecule is released as a product during the Kreb Cycle?
Which molecule is released as a product during the Kreb Cycle?
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What happens to the original oxaloacetate at the end of the Kreb Cycle?
What happens to the original oxaloacetate at the end of the Kreb Cycle?
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Which process occurs during the shuffling of carbon atoms in the Kreb Cycle?
Which process occurs during the shuffling of carbon atoms in the Kreb Cycle?
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Which enzyme initiates the Kreb Cycle by combining acetyl group with oxaloacetate?
Which enzyme initiates the Kreb Cycle by combining acetyl group with oxaloacetate?
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What is the result of the eight steps in the Kreb Cycle on the acetyl group?
What is the result of the eight steps in the Kreb Cycle on the acetyl group?
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What molecule is formed from alpha-ketoglutarate during the reaction catalyzed by alpha-ketoglutarate dehydrogenase?
What molecule is formed from alpha-ketoglutarate during the reaction catalyzed by alpha-ketoglutarate dehydrogenase?
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Which cofactor does alpha-ketoglutarate dehydrogenase use that is also utilized by pyruvate dehydrogenase?
Which cofactor does alpha-ketoglutarate dehydrogenase use that is also utilized by pyruvate dehydrogenase?
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What is released during the reaction catalyzed by alpha-ketoglutarate dehydrogenase?
What is released during the reaction catalyzed by alpha-ketoglutarate dehydrogenase?
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Which of the following statements is true about the reaction mechanism of alpha-ketoglutarate dehydrogenase?
Which of the following statements is true about the reaction mechanism of alpha-ketoglutarate dehydrogenase?
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During the reaction of alpha-ketoglutarate dehydrogenase, which component mediates the release of CO2?
During the reaction of alpha-ketoglutarate dehydrogenase, which component mediates the release of CO2?
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What does the remaining succinyl group get transferred to during the reaction catalyzed by alpha-ketoglutarate dehydrogenase?
What does the remaining succinyl group get transferred to during the reaction catalyzed by alpha-ketoglutarate dehydrogenase?
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Which of the following cofactors is not used by alpha-ketoglutarate dehydrogenase?
Which of the following cofactors is not used by alpha-ketoglutarate dehydrogenase?
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How does the mechanism of alpha-ketoglutarate dehydrogenase compare to other dehydrogenases?
How does the mechanism of alpha-ketoglutarate dehydrogenase compare to other dehydrogenases?
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Study Notes
The Krebs Cycle
- The Krebs Cycle, also known as the Citric Acid Cycle or Tricarboxylic Acid Cycle, is a crucial metabolic process.
- It's central to cellular metabolism, playing a vital role in energy production and biosynthesis.
- The cycle completes the breakdown of sugars started in glycolysis.
- It's a key part of producing ATP.
- It's also a hub for amino acid and other molecule synthesis.
- The cycle occurs in the mitochondrial matrix.
Krebs Cycle Overview
- The Krebs Cycle involves 8 metabolic reactions.
- The cycle uses a small molecule, oxaloacetate, as a starting and ending point.
- Acetyl-CoA combines with oxaloacetate to begin the cycle.
- The acetyl group is then broken down in 8 steps.
- Oxaloacetate is regenerated at the end of the cycle.
- Two carbon atoms are released as carbon dioxide in each cycle turn.
- The 8 reactions use enzymes.
Krebs Cycle Reactions (Detailed)
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Reaction 1: Citrate Synthase: Acetyl-CoA combines with oxaloacetate to form citrate. CoASH is released.
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Reaction 2: Aconitase: Citrate is isomerized to isocitrate. (Intermediate cis-aconitate exists).
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Reaction 3: Isocitrate Dehydrogenase: Isocitrate is oxidized and decarboxylated, forming α-ketoglutarate. NADH and CO2 are produced.
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Reaction 4: α-Ketoglutarate Dehydrogenase: α-ketoglutarate is oxidized and decarboxylated, producing succinyl-CoA, NADH, and CO2.
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Reaction 5: Succinyl-CoA Synthetase: Succinyl-CoA is converted to succinate, producing GTP (equivalent to ATP).
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Reaction 6: Succinate Dehydrogenase: Succinate is oxidized to fumarate, producing FADH2. This enzyme is part of the electron transport chain.
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Reaction 7: Fumarase: Fumarate is hydrated to form malate.
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Reaction 8: Malate Dehydrogenase: Malate is oxidized to oxaloacetate, producing NADH.
Energy Yield of the Krebs Cycle
- Per cycle, the process yields 3 NADH/H+, 1 FADH2, and 1 GTP.
- Per glucose molecule (2 cycles), the total yield translates to 6 NADH/H+, 2 FADH2, and 2 GTP.
Regulation of the Krebs Cycle
- The cycle is mainly controlled by three key dehydrogenase enzymes: pyruvate dehydrogenase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase.
- These enzymes are sensitive to energy levels in the cell.
- High levels of NADH, Acetyl-CoA, and ATP inhibit the cycle.
- Low levels of these molecules (e.g., high ADP) activate the cycle.
Beriberi
- A deficiency in vitamin B1 can cause Beriberi.
- This vitamin is essential for the TPP cofactor.
- Without sufficient TPP, the Krebs Cycle enzymes (PDH and α-ketoglutarate DH) function less efficiently, reducing ATP production.
- Low ATP levels lead to various symptoms like weight loss, emotional disturbances, and neurological/muscular issues.
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Description
Explore the intricate details of the Krebs Cycle, a fundamental metabolic process vital for energy production and biosynthesis. This quiz covers key reactions, the role of enzymes, and the regeneration of oxaloacetate. Test your knowledge on the steps involved in this critical cycle.
