Textbook Question
Glucose 6-phosphate is in a pivotal position in metabolism. Depending on conditions, glucose 6-phosphate follows one of several pathways. Under what conditions do the following occur?
d. Glycogenesis
Ch.22 Carbohydrate Metabolism
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 22, Problem 25c
Outline the conditions that direct pyruvate toward the following:
c. Conversion to lactate
In what tissues or organisms is each pathway present?
Verified step by step guidance1
Understand the context: Pyruvate is a key intermediate in cellular metabolism, and its fate depends on the availability of oxygen and the energy needs of the cell. Conversion to lactate occurs under anaerobic conditions (low oxygen levels).
Explain the biochemical pathway: Under anaerobic conditions, pyruvate is reduced to lactate by the enzyme lactate dehydrogenase. This process regenerates NAD⁺ from NADH, which is essential for glycolysis to continue producing ATP in the absence of oxygen.
Identify the conditions: The conversion of pyruvate to lactate typically occurs in tissues or organisms experiencing low oxygen availability, such as during intense exercise in human muscle cells or in certain microorganisms like lactic acid bacteria.
Discuss the role of lactate: In human muscle cells, lactate can accumulate during strenuous activity, leading to temporary muscle fatigue. However, lactate can later be transported to the liver, where it is converted back to glucose via the Cori cycle.
Summarize the tissues and organisms: The conversion of pyruvate to lactate is prominent in human muscle cells under anaerobic conditions and in microorganisms like lactic acid bacteria, which use this pathway for energy production in oxygen-deprived environments.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Pyruvate Metabolism
Pyruvate is a key intermediate in cellular metabolism, primarily produced from glycolysis. Its fate depends on the cellular environment, including oxygen availability. Under aerobic conditions, pyruvate enters the mitochondria for further oxidation, while under anaerobic conditions, it can be converted to lactate in a process called lactic acid fermentation.
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Pyruvate Oxidation Concept 1
Lactate Fermentation
Lactate fermentation is an anaerobic process where pyruvate is reduced to lactate by the enzyme lactate dehydrogenase. This process regenerates NAD+, allowing glycolysis to continue producing ATP in the absence of oxygen. It is particularly important in muscle cells during intense exercise and in certain microorganisms, such as lactic acid bacteria.
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Tissue and Organism Specificity
Different tissues and organisms utilize pyruvate differently based on their metabolic needs and oxygen availability. For instance, human muscle cells convert pyruvate to lactate during strenuous activity, while liver cells primarily convert it to glucose via gluconeogenesis. In contrast, some anaerobic bacteria rely exclusively on lactate fermentation for energy production.
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Related Practice
Textbook Question
Fatty acids from stored triacylglycerols (fat) are not available for gluconeogenesis. Speculate why we do not have the enzymes to directly convert fatty acids into glucose. Plants (especially seeds) do have enzymes to convert fatty acids into carbohydrates. Why are they so lucky?
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?
Textbook Question
Glucose 6-phosphate is in a pivotal position in metabolism. Depending on conditions, glucose 6-phosphate follows one of several pathways. Under what conditions do the following occur?
b. Hydrolysis to free glucose
Textbook Question
Name the molecules used for gluconeogenesis. What are the sources of these molecules? Under what conditions would gluconeogenesis occur?
Textbook Question
Outline the conditions that direct pyruvate toward the following:
d. Glucose synthesis (gluconeogenesis)
In what tissues or organisms is each pathway present?