Textbook Question
Three metabolites that can result from the breakdown of the carbon skeleton of amino acids are ketone bodies, acetyl-CoA, and glucose. Briefly describe how each of these metabolites can be produced from amino acid catabolism.
Ch.25 Protein and Amino Acid 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 25, Problem 3
What is the structure of the α-keto acid formed by transamination of the amino acid phenylalanine (Phe)?
Verified step by step guidance1
Understand the process of transamination: Transamination is a biochemical reaction where an amino group (-NH₂) from an amino acid is transferred to an α-keto acid, resulting in the formation of a new amino acid and a new α-keto acid. In this case, we are focusing on the α-keto acid formed when phenylalanine undergoes transamination.
Identify the structure of phenylalanine: Phenylalanine (Phe) is an amino acid with the structure C₆H₅-CH₂-CH(NH₂)-COOH. It contains a benzyl side chain (C₆H₅-CH₂) attached to the α-carbon, which is also bonded to an amino group (-NH₂) and a carboxylic acid group (-COOH).
Determine the α-keto acid product: During transamination, the amino group (-NH₂) on the α-carbon of phenylalanine is replaced by a keto group (=O). This results in the formation of an α-keto acid. The general structure of the α-keto acid is C₆H₅-CH₂-CO-COOH.
Write the structure of the α-keto acid: The α-keto acid formed from phenylalanine is phenylpyruvic acid. Its structure is C₆H₅-CH₂-CO-COOH, where the benzyl group (C₆H₅-CH₂) remains unchanged, and the α-carbon now has a keto group (=O) instead of the amino group.
Verify the reaction: Confirm that the transamination reaction conserves the carbon skeleton of phenylalanine while replacing the amino group with a keto group. This ensures the correct α-keto acid, phenylpyruvic acid, is identified as the product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Transamination
Transamination is a biochemical process that involves the transfer of an amino group from an amino acid to a keto acid. This reaction is crucial in amino acid metabolism, allowing the synthesis of new amino acids and the conversion of amino acids into intermediates for energy production. In the case of phenylalanine, transamination will yield a corresponding α-keto acid, which is essential for understanding its metabolic fate.
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α-Keto Acid
An α-keto acid is a type of organic compound that contains a keto group (C=O) adjacent to a carboxylic acid group (–COOH). These compounds play a significant role in metabolism, particularly in the Krebs cycle and amino acid catabolism. The α-keto acid formed from phenylalanine through transamination is crucial for understanding its structural and functional implications in metabolic pathways.
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Phenylalanine Structure
Phenylalanine is an essential amino acid characterized by its aromatic side chain, which consists of a phenyl group attached to an α-carbon. Its structure is vital for understanding how it participates in transamination reactions. By referring to Table 18.3, one can visualize the specific arrangement of atoms in phenylalanine, which directly influences the structure of the resulting α-keto acid after the transamination process.
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Related Practice
Textbook Question
Unlike most amino acids, branched-chain amino acids are broken down in tissues other than the liver. Using Table 18.3, identify the three amino acids with branched-chain R groups. For any one of these amino acids, write the equation for its transamination.
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Textbook Question
Fumarate from step 3 of the urea cycle may be recycled into aspartate for use in step 2 of the cycle. The sequence of reactions for this process is
a.
b.
c.
Classify each reaction as one of the following:
1. Oxidation
2. Reduction
3. Transamination
4. Elimination
5. Addition
Textbook Question
Serotonin is a monoamine neurotransmitter. It is formed in the body from the amino acid tryptophan. What class of enzyme catalyzes each of the two steps that convert tryptophan to serotonin?
Textbook Question
Decide whether each of the following statements is true or false. If false, explain why.
a. The amino acid pool is found mainly in the liver.