Textbook Question
Outline the conditions that direct pyruvate toward the following:
b. Conversion to ethanol and CO2
In what tissues or organisms is each pathway present?
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22. Carbohydrate Metabolism
Anaerobic Respiration
2:19 minutesProblem 77
Textbook Question
Why is it important for the cell that the NADH produced when pyruvate is converted to lactate be converted back to NAD+?
Verified step by step guidance1
Understand the context: During anaerobic conditions (low oxygen), cells rely on glycolysis to produce ATP. Glycolysis requires NAD⁺ as a coenzyme to accept electrons during the oxidation of glucose to pyruvate.
Recognize the issue: If NAD⁺ is not regenerated, glycolysis will stop because there will be no NAD⁺ available to accept electrons, halting ATP production and leading to energy depletion in the cell.
Explain the role of lactate formation: When pyruvate is converted to lactate by the enzyme lactate dehydrogenase, NADH is oxidized back to NAD⁺. This reaction ensures a continuous supply of NAD⁺ for glycolysis to proceed.
Connect to cellular survival: The regeneration of NAD⁺ is critical for maintaining ATP production under anaerobic conditions, which is especially important for cells like muscle cells during intense exercise or for cells in low-oxygen environments.
Summarize the importance: The conversion of NADH to NAD⁺ during lactate formation is a key step in sustaining energy production and preventing metabolic shutdown in the absence of oxygen.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
NADH and NAD⁺ Role in Metabolism
NADH and NAD⁺ are crucial coenzymes in cellular metabolism, particularly in redox reactions. NADH acts as a reducing agent, donating electrons during metabolic processes, while NAD⁺ serves as an oxidizing agent, accepting electrons. The interconversion between these two forms is vital for maintaining the balance of redox reactions in the cell.
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Lactate Fermentation
Lactate fermentation is an anaerobic process where pyruvate is converted to lactate, allowing glycolysis to continue in the absence of oxygen. This process regenerates NAD⁺ from NADH, which is essential for glycolysis to produce ATP. Without this regeneration, glycolysis would halt, leading to a lack of energy production in the cell.
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Cellular Energy Production
Cellular energy production primarily occurs through glycolysis, the Krebs cycle, and oxidative phosphorylation. In anaerobic conditions, the conversion of pyruvate to lactate ensures that glycolysis can continue by replenishing NAD⁺. This is critical for cells, especially muscle cells during intense exercise, to sustain ATP production when oxygen is limited.
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