Textbook Question
What is the major purpose of the pentose phosphate pathway? What cofactor (coenzyme) is used?
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 36
What three products are formed from pyruvate under aerobic, anaerobic, and fermentation conditions?
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Under aerobic conditions, pyruvate is transported into the mitochondria where it undergoes oxidative decarboxylation by the enzyme pyruvate dehydrogenase. This process converts pyruvate into acetyl-CoA, releasing one molecule of CO₂ and reducing NAD⁺ to NADH.
Under anaerobic conditions in animal cells, pyruvate is reduced to lactate in the cytoplasm by the enzyme lactate dehydrogenase. This process regenerates NAD⁺ from NADH, allowing glycolysis to continue in the absence of oxygen.
Under fermentation conditions in yeast and some microorganisms, pyruvate is converted into ethanol and CO₂. This occurs in two steps: first, pyruvate is decarboxylated to acetaldehyde by the enzyme pyruvate decarboxylase, releasing CO₂. Then, acetaldehyde is reduced to ethanol by alcohol dehydrogenase, regenerating NAD⁺.
Each of these pathways serves a specific purpose: aerobic respiration maximizes ATP production, anaerobic respiration allows glycolysis to continue in low oxygen conditions, and fermentation enables energy production in microorganisms under anaerobic conditions.
To summarize, the three products formed from pyruvate are: acetyl-CoA (aerobic), lactate (anaerobic), and ethanol + CO₂ (fermentation).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Pyruvate
Pyruvate is a key intermediate in cellular metabolism, produced from glucose during glycolysis. It serves as a crucial junction point for various metabolic pathways, determining the fate of glucose-derived energy depending on the availability of oxygen.
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Pyruvate Oxidation Concept 2
Aerobic Respiration
Aerobic respiration is a metabolic process that occurs in the presence of oxygen, where pyruvate is converted into acetyl-CoA and enters the citric acid cycle. This process generates a significant amount of ATP, carbon dioxide, and water as byproducts, making it highly efficient for energy production.
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Anaerobic Respiration and Fermentation
Anaerobic respiration and fermentation occur in the absence of oxygen. In anaerobic respiration, pyruvate can be converted into substances like lactic acid or ethanol, depending on the organism. Fermentation is a specific type of anaerobic process that allows for ATP production without the electron transport chain, resulting in products like ethanol in yeast or lactic acid in muscle cells.
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Related Practice
Textbook Question
The pathway that converts glucose to acetyl-CoA is often referred to as an “aerobic oxidation pathway.”
(b) Thinking back to Chapter 20, where does molecular oxygen enter the picture?
Textbook Question
What are the products of digestion of proteins, triacylglycerols, maltose, sucrose, lactose, and starch?
Textbook Question
What are the major monosaccharide products produced by digestion of carbohydrates?
Textbook Question
Which cells, liver, muscle, or brain, use the following pathways?
a. Glycolysis
Textbook Question
Which cells, liver, muscle, or brain, use the following pathways?
b. Gluconeogenesis