Textbook Question
Consider the trisaccharide A, B, C shown in Problem 20.23.
a. Identify the hemiacetal and acetal linkages.
Ch.20 Carbohydrates
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 20, Problem 20
During the digestion of starch from potatoes, the enzyme α-amylase catalyzes the hydrolysis of starch into maltose. Subsequently, the enzyme maltase catalyzes the hydrolysis of maltose into two glucose units. Write an equation (in words) for the enzymatic conversion of starch to glucose. Classify each of the carbohydrates in the equation as a disaccharide, monosaccharide, or polysaccharide.
Verified step by step guidance1
Step 1: Understand the enzymatic process. The problem describes two enzymatic reactions: (1) α-amylase catalyzes the breakdown of starch into maltose, and (2) maltase catalyzes the breakdown of maltose into glucose. These reactions involve hydrolysis, where water is used to break chemical bonds.
Step 2: Write the first reaction in words. Starch, a polysaccharide, is hydrolyzed by the enzyme α-amylase to produce maltose, which is a disaccharide. The reaction can be written as: 'Starch + Water → Maltose (catalyzed by α-amylase)'.
Step 3: Write the second reaction in words. Maltose, a disaccharide, is hydrolyzed by the enzyme maltase to produce two glucose molecules, which are monosaccharides. The reaction can be written as: 'Maltose + Water → 2 Glucose (catalyzed by maltase)'.
Step 4: Combine the two reactions into a single overall equation. The enzymatic conversion of starch to glucose can be summarized as: 'Starch + Water → Glucose (via α-amylase and maltase)'.
Step 5: Classify the carbohydrates. Starch is a polysaccharide, maltose is a disaccharide, and glucose is a monosaccharide. This classification is based on the number of sugar units in each molecule: polysaccharides have many, disaccharides have two, and monosaccharides have one.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enzymatic Hydrolysis
Enzymatic hydrolysis is a biochemical process where enzymes catalyze the breakdown of complex molecules into simpler ones by adding water. In the context of starch digestion, α-amylase initiates this process by breaking down starch, a polysaccharide, into maltose, a disaccharide. This reaction is crucial for converting carbohydrates into absorbable sugars.
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Carbohydrate Classification
Carbohydrates are classified into three main categories: monosaccharides, disaccharides, and polysaccharides. Monosaccharides are the simplest form, consisting of single sugar units like glucose. Disaccharides, such as maltose, are formed from two monosaccharides, while polysaccharides, like starch, are long chains of monosaccharide units. Understanding these classifications is essential for analyzing the enzymatic conversion process.
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Enzyme Function
Enzymes are biological catalysts that speed up chemical reactions in living organisms without being consumed in the process. In starch digestion, α-amylase and maltase are specific enzymes that facilitate the conversion of starch to glucose by lowering the activation energy required for the hydrolysis reactions. Their specificity and efficiency are vital for proper digestion and nutrient absorption.
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Related Practice
Textbook Question
Draw the structure of the α and β anomers that result from the reaction of methanol and ribose. Are these compounds acetals or hemiacetals?
Textbook Question
L-Fucose is one of the naturally occurring L monosaccharides. It is present in the short chains of monosaccharides by which blood groups are classified. Compare the structure of L-fucose shown in the margin with the structures of α- and β-D-galactose and answer the following questions.
d. "Fucose” is a common name. Is 6-deoxy-L-galactose a correct name for fucose? Why or why not?
Textbook Question
How would you classify the link between the monosaccharides in cellobiose?
Textbook Question
Consider the trisaccharide A, B, C shown in Problem 20.23.
c. State the numbers of the carbon atoms that form glycosidic linkages between monosaccharide A and monosaccharide B.
Textbook Question
Identify the following as diastereomers, enantiomers, and/or anomers.
(a) β-D-fructose and β-D-fructose
(b) D-galactose and L-galactose
(c) L-allose and D-glucose (both aldohexoses)