Textbook Question
Draw the pH–activity profile for an enzyme that has one catalytic group at the active site:
a. the catalytic group is a general-acid catalyst with a pKa = 5.6.
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Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 22 - Catalysis in Organic Reactions and in Enzymatic ReactionsProblem 24
Bruice 8th EditionCh. 22 - Catalysis in Organic Reactions and in Enzymatic ReactionsProblem 24Chapter 23, Problem 24
Draw the mechanism for the hydroxide ion–catalyzed cleavage of fructose-1,6-bisphosphate.
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Identify the structure of fructose-1,6-bisphosphate. It is a six-carbon sugar with phosphate groups attached to the first and sixth carbons. The molecule contains a ketone functional group at the second carbon and hydroxyl groups on the remaining carbons.
Recognize that the reaction is catalyzed by hydroxide ions (OH⁻), which act as a nucleophile. Hydroxide ions will attack the electrophilic carbonyl carbon of the ketone group in fructose-1,6-bisphosphate.
Draw the nucleophilic attack of the hydroxide ion on the carbonyl carbon of the ketone group. This forms a tetrahedral intermediate, where the carbonyl oxygen becomes negatively charged.
Illustrate the breakdown of the tetrahedral intermediate. The negatively charged oxygen reforms the carbonyl group, leading to the cleavage of the C3-C4 bond. This results in the formation of two products: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P).
Show the stabilization of the products. Both DHAP and G3P are stabilized by resonance and the presence of phosphate groups, which help to delocalize the negative charge. Ensure the final structures of the products are clearly drawn with proper stereochemistry and functional groups.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enzyme Catalysis
Enzyme catalysis involves the acceleration of chemical reactions by enzymes, which are biological catalysts. In the context of fructose-1,6-bisphosphate cleavage, enzymes like aldolase facilitate the reaction by lowering the activation energy, allowing the reaction to proceed more efficiently. Understanding how enzymes interact with substrates is crucial for grasping the mechanism of this reaction.
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Nucleophilic Catalysis Concept 1
Mechanism of Hydrolysis
The mechanism of hydrolysis refers to the chemical process where water is used to break down a compound. In the case of fructose-1,6-bisphosphate, hydroxide ions act as nucleophiles, attacking the carbonyl carbon of the phosphate group, leading to the cleavage of the molecule. Familiarity with nucleophilic attack and the role of water in hydrolysis is essential for understanding this reaction.
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0:55Hydrolysis of Nucleosides Concept 1
Phosphate Group Cleavage
Phosphate group cleavage is a critical reaction in biochemistry, where a phosphate group is removed from a molecule, often releasing energy. In the cleavage of fructose-1,6-bisphosphate, the breaking of the phosphate bond is a key step that leads to the formation of two three-carbon molecules. Recognizing the significance of phosphate groups in metabolic pathways is vital for comprehending the overall reaction.
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0:48Hydrolysis of Phosphate Esters Concept 2
Related Practice
Textbook Question
In glycolysis, why must glucose-6-phosphate isomerize to fructose-6-phosphate (Section 22.12 ) before the cleavage reaction with aldolase occurs?
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Textbook Question
Draw the pH–activity profile for an enzyme that has one catalytic group at the active site:
b. the catalytic group is a general-base catalyst with a pKa = 7.2.
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Textbook Question
Aldolase shows no activity if it is incubated with iodoacetic acid before fructose-1,6-bisphosphate is added to the reaction mixture. What causes this loss of activity?
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Textbook Question
Which of the following amino acid side chains can form an imine with a substrate?
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Textbook Question
The pH–activity profile for glucose-6-phosphate isomerase indicates the participation of a group with a pKa = 6.7 as a basic catalyst and a group with a pKa = 9.3 as an acid catalyst. Draw the pH–activity profile and identify the amino acids that participate in the catalysis.
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