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Ch.18 Metabolic Pathways and ATP Production
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 14th Edition
Timberlake14th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9781292472249Not the one you use?Change textbook
All textbooksTimberlake 14th EditionCh.18 Metabolic Pathways and ATP ProductionProblem 30
Chapter 18, Problem 30

What coenzymes are needed for the oxidation of pyruvate to acetyl CoA?

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Understand the context: Pyruvate oxidation is a key step in cellular respiration where pyruvate is converted into acetyl CoA, which then enters the citric acid cycle. This process occurs in the mitochondria and requires specific coenzymes to facilitate the reaction.
Identify the enzyme complex involved: The enzyme responsible for this reaction is the pyruvate dehydrogenase complex (PDC), which catalyzes the oxidative decarboxylation of pyruvate.
List the coenzymes required: The pyruvate dehydrogenase complex requires several coenzymes to function. These include: (1) Thiamine pyrophosphate (TPP), (2) Lipoic acid (lipoamide), (3) Coenzyme A (CoA), (4) Flavin adenine dinucleotide (FAD), and (5) Nicotinamide adenine dinucleotide (NAD⁺).
Explain the role of each coenzyme: (1) TPP helps in the decarboxylation of pyruvate. (2) Lipoic acid acts as a carrier of acyl groups and electrons. (3) CoA accepts the acetyl group to form acetyl CoA. (4) FAD is involved in electron transfer within the enzyme complex. (5) NAD⁺ accepts electrons to form NADH, which is used in further energy production.
Summarize the reaction: Pyruvate is oxidized to acetyl CoA with the help of the pyruvate dehydrogenase complex and the coenzymes TPP, lipoic acid, CoA, FAD, and NAD⁺. This reaction also produces NADH and releases CO₂ as a byproduct.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Pyruvate Oxidation

Pyruvate oxidation is a crucial metabolic process that occurs in the mitochondria, where pyruvate, derived from glycolysis, is converted into acetyl CoA. This reaction is catalyzed by the pyruvate dehydrogenase complex and is essential for linking glycolysis to the citric acid cycle, allowing for further energy production.

Coenzymes in Metabolism

Coenzymes are organic molecules that assist enzymes in catalyzing biochemical reactions. In the context of pyruvate oxidation, key coenzymes include NAD+ and Coenzyme A (CoA). NAD+ is reduced to NADH during the process, while CoA is essential for forming acetyl CoA, which enters the citric acid cycle.
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NAD+ and Coenzyme A

NAD+ (Nicotinamide adenine dinucleotide) acts as an electron carrier, accepting electrons during the oxidation of pyruvate, which is vital for energy production. Coenzyme A (CoA) is a carrier of acyl groups and is crucial for the formation of acetyl CoA from pyruvate, enabling its entry into the citric acid cycle for further energy extraction.
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Related Practice
Textbook Question

How many ATP or NADH are produced (or required) in each of the following steps in glycolysis?

c. phosphoenolpyruvate to pyruvate

Textbook Question

How does the formation of lactate permit glycolysis to continue under anaerobic conditions?

Textbook Question

How is ATP used in the initial steps of glycolysis?

Textbook Question

How many ATP or NADH are produced (or required) in each of the following steps in glycolysis?

a. glucose to glucose-6-phosphate

Textbook Question

What are the products from one turn of the citric acid cycle?

Textbook Question

Identify the reaction(s) of the citric acid cycle that involve(s)

a. oxidation and decarboxylation