Questions and Answers
Which molecule is reduced to form NADH during the Krebs cycle?
What molecule is produced as a result of the decarboxylation of isocitrate?
Which step in the Krebs cycle involves the conversion of fumarate to malate?
What is formed when FAD is reduced during the Krebs cycle?
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In which step of the Krebs cycle is carbon dioxide produced?
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What is the main enzymatic function of fumarase in the Krebs cycle?
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Which enzyme catalyzes the step involving the conversion of α-ketoglutarate to succinyl-CoA?
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What role does CO2 play in the Krebs cycle?
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Which reduction product of the Krebs cycle carries electrons to the electron transport chain?
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During which step does the substrate-level phosphorylation occur in the Krebs cycle?
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Study Notes
Krebs Cycle (Citric Acid Cycle)
- Acetyl CoA enters the cycle, combining with oxaloacetate to form 6C citrate.
- CoA is stripped from Acetyl CoA and recycled during the process.
- Key enzymes, such as citrate synthase, facilitate reactions throughout the cycle.
- NAD+ and FAD are reduced to NADH and FADH2, respectively, during various oxidation steps.
- Completion of the cycle regenerates oxaloacetate, allowing the process to continue.
Electron Transport Chain
- Occurs across the inner mitochondrial membrane, where oxygen acts as the final electron acceptor, producing H2O.
- NADH generated from the Krebs cycle and glycolysis contributes significantly to ATP production.
- Each NADH yields approximately 2.5 ATP; 8 NADH can produce around 20 ATP.
- FADH2 produces about 1.5 ATP; 2 FADH2 yield approximately 3 ATP.
- NADH from glycolysis (cytosolic) cannot enter the mitochondrial matrix directly due to impermeability of the inner mitochondrial membrane.
ATP Generation
- Total ATP produced can vary between 26 to 28 ATP, depending on whether NADH or FADH2 is used for generating ATP through oxidative phosphorylation.
- Substrate-level phosphorylation in the Krebs cycle contributes directly to ATP formation.
Additional Cycle Steps
- Isocitrate undergoes oxidation and decarboxylation, losing CO2 to form α-ketoglutarate.
- The cycle includes crucial steps involving the transfer of hydrogens and the formation of intermediate compounds such as fumarate.
- Each step carefully regulates the conversion and utilization of energy carriers, vital for cellular respiration.
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Description
Test your knowledge on ATP synthesis and substrate-level phosphorylation. This quiz covers key concepts and reactions involving FAD, NADH, and ATP production. Challenge yourself and see how well you understand the biochemical processes involved in energy metabolism.
