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

Timberlake 14th Edition

Ch.18 Metabolic Pathways and ATP Production

Problem 33

Chapter 18, Problem 33

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

Verified step by step guidance

Understand the context: Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, producing ATP and NADH. Under anaerobic conditions (absence of oxygen), the electron transport chain cannot regenerate NAD⁺ from NADH, which is essential for glycolysis to continue.

Recognize the role of lactate formation: In anaerobic conditions, cells convert pyruvate into lactate through the enzyme lactate dehydrogenase. This reaction is crucial because it regenerates NAD⁺ from NADH.

Write the chemical reaction: The conversion can be represented as:

pyruvate + {NADH}_{2 ⟶ lactate + NAD}

⁺. This ensures a continuous supply of NAD⁺ for glycolysis.

Explain the importance of NAD⁺: NAD⁺ is a coenzyme required for the oxidation of glyceraldehyde-3-phosphate in glycolysis. Without sufficient NAD⁺, glycolysis would halt, and the cell would be unable to produce ATP under anaerobic conditions.

Summarize the process: The formation of lactate allows cells to maintain ATP production through glycolysis by regenerating NAD⁺, even when oxygen is not available to support aerobic respiration.

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Key Concepts

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

Glycolysis

Glycolysis is a metabolic pathway that converts glucose into pyruvate, producing a small amount of ATP and NADH in the process. It occurs in the cytoplasm and can function under both aerobic and anaerobic conditions. Understanding glycolysis is essential for grasping how energy is generated in cells, especially when oxygen is limited.

Anaerobic Conditions

Anaerobic conditions refer to environments where oxygen is scarce or absent. In such conditions, cells must rely on alternative metabolic pathways to generate energy. This is crucial for organisms that live in low-oxygen environments and for muscle cells during intense exercise, where oxygen supply may not meet demand.

Lactate Formation

Lactate formation occurs when pyruvate, the end product of glycolysis, is converted into lactate by the enzyme lactate dehydrogenase. This process regenerates NAD+, which is necessary for glycolysis to continue under anaerobic conditions. By converting pyruvate to lactate, cells can sustain ATP production even when oxygen is not available.