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Questions and Answers
Which of the following correctly identifies the process that produces ATP and involves oxidative phosphorylation?
Which of the following correctly identifies the process that produces ATP and involves oxidative phosphorylation?
What is the final product regenerated in the Krebs cycle that allows it to continue operating?
What is the final product regenerated in the Krebs cycle that allows it to continue operating?
Which of the following compounds is not directly produced during the Krebs cycle?
Which of the following compounds is not directly produced during the Krebs cycle?
In metabolic pathways, which term describes the process that builds larger molecules from smaller units?
In metabolic pathways, which term describes the process that builds larger molecules from smaller units?
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Which metabolic process occurs when oxygen is absent and results in a net gain of 2 ATP?
Which metabolic process occurs when oxygen is absent and results in a net gain of 2 ATP?
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Which B vitamin functions as NAD+ and NADH in metabolic pathways?
Which B vitamin functions as NAD+ and NADH in metabolic pathways?
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What role does Riboflavin play in energy metabolism?
What role does Riboflavin play in energy metabolism?
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Which B vitamin is essential for the synthesis of acetyl CoA?
Which B vitamin is essential for the synthesis of acetyl CoA?
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Which B vitamin is represented by TPP in metabolic processes?
Which B vitamin is represented by TPP in metabolic processes?
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Without which B vitamin would the human body struggle to utilize fats, carbohydrates, and proteins?
Without which B vitamin would the human body struggle to utilize fats, carbohydrates, and proteins?
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What does the coenzyme form of Pantothenic acid participate in during metabolism?
What does the coenzyme form of Pantothenic acid participate in during metabolism?
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Which of the following is NOT a function associated with B vitamins in metabolism?
Which of the following is NOT a function associated with B vitamins in metabolism?
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Which of the following pairs a B vitamin with its respective coenzyme form?
Which of the following pairs a B vitamin with its respective coenzyme form?
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What is the primary role of Complex I in the electron transport chain?
What is the primary role of Complex I in the electron transport chain?
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Which subunits are integral components of Complex I?
Which subunits are integral components of Complex I?
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What occurs during the first electron transfer step in Complex I?
What occurs during the first electron transfer step in Complex I?
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Which of the following statements about Complex II is true?
Which of the following statements about Complex II is true?
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What do coenzyme Q and cytochrome c function as in the electron transport chain?
What do coenzyme Q and cytochrome c function as in the electron transport chain?
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Which complex is responsible for the final step of electron transfer in the electron transport chain?
Which complex is responsible for the final step of electron transfer in the electron transport chain?
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What is the end product when NADH is oxidized in Complex I?
What is the end product when NADH is oxidized in Complex I?
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In terms of composition, what is Complex V primarily known for?
In terms of composition, what is Complex V primarily known for?
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What does the breaking of the thioester bond in succinyl CoA release?
What does the breaking of the thioester bond in succinyl CoA release?
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Which enzyme catalyzes the oxidation of succinate in the citric acid cycle?
Which enzyme catalyzes the oxidation of succinate in the citric acid cycle?
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What type of reaction is involved in Step 6 of the citric acid cycle?
What type of reaction is involved in Step 6 of the citric acid cycle?
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What product is formed when FAD is reduced in the oxidation of succinate?
What product is formed when FAD is reduced in the oxidation of succinate?
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Which compound is regenerated from the oxidation of L-malate?
Which compound is regenerated from the oxidation of L-malate?
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What is the role of NAD+ in Step 8 of the citric acid cycle?
What is the role of NAD+ in Step 8 of the citric acid cycle?
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What does the electron transport chain ultimately produce from molecular oxygen?
What does the electron transport chain ultimately produce from molecular oxygen?
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In the electron transport chain, what happens to electrons as they pass through the chain?
In the electron transport chain, what happens to electrons as they pass through the chain?
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What is the primary 'fuel' for the citric acid cycle?
What is the primary 'fuel' for the citric acid cycle?
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Which oxidizing agent is used when a carbon–carbon double bond is formed during the cycle?
Which oxidizing agent is used when a carbon–carbon double bond is formed during the cycle?
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During one turn of the citric acid cycle, how many molecules of CO2 are released?
During one turn of the citric acid cycle, how many molecules of CO2 are released?
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How many times does the citric acid cycle operate for each molecule of glucose?
How many times does the citric acid cycle operate for each molecule of glucose?
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What is the major role of NADH and FADH2 produced in the citric acid cycle?
What is the major role of NADH and FADH2 produced in the citric acid cycle?
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What occurs during the redox reactions of the citric acid cycle?
What occurs during the redox reactions of the citric acid cycle?
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Which statement is true regarding the carbon atoms entering and leaving the citric acid cycle?
Which statement is true regarding the carbon atoms entering and leaving the citric acid cycle?
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What would happen if NAD+ and FAD were not available during the cycle?
What would happen if NAD+ and FAD were not available during the cycle?
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Study Notes
Electron Transport Chain
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The electron transport chain (ETC) is a sequence of biochemical reactions where electrons from NADH and FADH2 are transferred to various intermediate carriers before reacting with molecular oxygen to form water.
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NADH and FADH2 are oxidized in this process.
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The energy from the electrons is used to pump protons across the mitochondrial membrane, creating a proton gradient that is used to drive ATP synthesis.
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Four protein complexes, tightly bound to the membrane, participate in the ETC:
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Complex I (NADH–coenzyme Q reductase): This complex transfers electrons from NADH to coenzyme Q (CoQ), also known as ubiquinone.
- Complex I contains more than 40 subunits, including FMN (flavin mononucleotide) and iron-sulfur proteins.
- Complex II (Succinate–coenzyme Q reductase): This complex transfers electrons from succinate to CoQ.
- Complex III (Coenzyme Q–cytochrome c reductase): This complex transfers electrons from CoQ to cytochrome c.
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Complex IV (Cytochrome c oxidase): This complex transfers electrons from cytochrome c to molecular oxygen, forming water.
- Complex IV is a heme and copper containing complex.
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Complex I (NADH–coenzyme Q reductase): This complex transfers electrons from NADH to coenzyme Q (CoQ), also known as ubiquinone.
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Two mobile electron carriers, CoQ and cytochrome c, shuttle electrons between the complexes.
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The citric acid cycle provides NADH as a source of electrons for the ETC.
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Vitamins are crucial for the ETC and citric acid cycle.
- Niacin: Contributes to NAD+/NADH.
- Riboflavin: Contributes to FAD, FADH2, and FMN.
- Thiamin: Contributes to TPP (thiamin pyrophosphate).
- Pantothenic acid: Contributes to CoA (coenzyme A).
Citric Acid Cycle
- The citric acid cycle, also known as the Krebs cycle, is a series of reactions that oxidize acetyl-CoA to carbon dioxide, generating reducing equivalents (NADH and FADH2) that are used in the ETC.
- The citric acid cycle takes place in the mitochondria.
- Acetyl-CoA, derived from the breakdown of carbohydrates, fats, and proteins, is the fuel for the cycle.
- The cycle consists of eight steps:
- Step 1: Acetyl-CoA combines with oxaloacetate to form citrate.
- Step 2: Citrate is converted to isocitrate.
- Step 3: Isocitrate is oxidized and decarboxylated to α-ketoglutarate, producing NADH and carbon dioxide.
- Step 4: α-Ketoglutarate is oxidized and decarboxylated to succinyl-CoA, producing NADH and carbon dioxide.
- Step 5: Succinyl-CoA is converted to succinate, producing GTP (guanosine triphosphate), which is subsequently converted to ATP.
- Step 6: Succinate is oxidized to fumarate, producing FADH2.
- Step 7: Fumarate is hydrated to malate.
- Step 8: Malate is oxidized to oxaloacetate, producing NADH, regenerating oxaloacetate to continue the cycle.
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Description
Explore the intricacies of the electron transport chain, where electrons from NADH and FADH2 are utilized to create a proton gradient in mitochondria. Learn about the four main protein complexes involved in this vital biochemical process and their roles in ATP synthesis. Test your knowledge on this essential part of cellular respiration.
