Carbohydrate Structural Isomerism
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Questions and Answers

What is the primary difference between aldohexoses and ketohexoses in terms of ring formation?

  • Aldohexoses form open-chain structures, while ketohexoses form ring structures
  • Aldohexoses form 5-membered rings, while ketohexoses form 6-membered rings
  • Aldohexoses form furanose rings, while ketohexoses form pyranose rings
  • Aldohexoses form 6-membered rings, while ketohexoses form 5-membered rings (correct)

    • What is the name of the type of isomerism exhibited by glucose and galactose?

  • Diastereomers
  • Enantiomers
  • Structural isomers
  • Epimers (correct)

    • What is the shape of the 6-membered ring formed by aldohexoses in solution?

  • Planar
  • Pyranose ring
  • Chair formation (correct)
  • Furanose ring

    • What is the term for molecules that have the same structural formula but differ in spatial configuration?

    <p>Stereoisomers</p> Signup and view all the answers

    How many aldoses and ketoses can be identified in hexose sugars?

    <p>8 aldoses and 4 ketoses</p> Signup and view all the answers

    What type of reaction occurs between the –OH group and a C=O in hexose sugars to form rings?

    <p>Hemiacetal formation</p> Signup and view all the answers

    What is common to all monosaccharides except dihydroxyacetone?

    <p>They contain 1 or more asymmetric carbons</p> Signup and view all the answers

    What is the difference between D-glyceraldehyde and L-glyceraldehyde?

    <p>They are mirror images of each other</p> Signup and view all the answers

    What is an epimer?

    <p>An isomer that differs due to the H and OH configuration of carbons 2, 3, or 4</p> Signup and view all the answers

    What is the term for isomers that differ in their spatial configuration but are not mirror images?

    <p>Diastereoisomers</p> Signup and view all the answers

    What is the relationship between D-glucose and D-mannose?

    <p>They are epimers at C-2</p> Signup and view all the answers

    What is the term for the carbon atom that becomes asymmetric during cyclisation?

    <p>Anomeric carbon</p> Signup and view all the answers

    What is the influence of asymmetric carbons or chirality on compounds?

    <p>It increases their optical activity</p> Signup and view all the answers

    What is formed when a sugar molecule undergoes cyclisation?

    <p>A Haworth structure</p> Signup and view all the answers

    What is the classification of carbohydrates based on the number of carbon atoms present in their structures?

    <p>Trioses, Tetroses, Pentoses, Hexoses</p> Signup and view all the answers

    What is the difference between aldoses and ketoses?

    <p>Aldoses have an aldehyde group, while ketoses have a ketone group</p> Signup and view all the answers

    What is the classification of isomers based on their spatial arrangement?

    <p>Structural isomers and Stereo-isomers</p> Signup and view all the answers

    Which of the following is an example of a 4-carbon monosaccharide?

    <p>Erythrose</p> Signup and view all the answers

    What is the characteristic of monosaccharides?

    <p>They are water-soluble white crystalline solids with a sweet taste</p> Signup and view all the answers

    What is the difference between erythrose and erythulose?

    <p>Erythrose is an aldose, while erythulose is a ketose</p> Signup and view all the answers

    What is the term for isomers that have the same number and kinds of atoms, but differ in their structural or spatial configurations?

    <p>Stereo-isomers</p> Signup and view all the answers

    What is the characteristic of monosaccharides in terms of hydrolysis?

    <p>They cannot be hydrolyzed into simpler forms of carbohydrates</p> Signup and view all the answers

    What is the characteristic of monosaccharides that makes them unable to be hydrolyzed into simpler forms of carbohydrates?

    <p>They are already in their simplest form.</p> Signup and view all the answers

    What is the classification of carbohydrates based on the number of carbon atoms present in their structures?

    <p>They are classified into trioses, tetroses, pentoses, hexoses, and heptoses based on the number of carbon atoms present in their structures.</p> Signup and view all the answers

    What is the difference between aldoses and ketoses?

    <p>Aldoses have an aldehyde group, while ketoses have a ketone group.</p> Signup and view all the answers

    What is the term for isomers that have the same number and kinds of atoms, but differ in their structural or spatial configurations?

    <p>They are called structural isomers.</p> Signup and view all the answers

    What type of ring structure do aldohexoses form in solution?

    <p>6-membered rings</p> Signup and view all the answers

    What is the characteristic of monosaccharides in terms of their physical properties?

    <p>They are water-soluble, white crystalline solids with a sweet taste.</p> Signup and view all the answers

    How do ketohexoses and aldopentoses differ in ring formation?

    <p>They form 5-membered rings.</p> Signup and view all the answers

    What is the term for molecules that have the same structural formula but differ in spatial configuration?

    <p>Stereoisomers</p> Signup and view all the answers

    What is the significance of erythrose and erythulose as examples of 4-carbon monosaccharides?

    <p>They are examples of aldose and ketose isomers, respectively, with the same number of carbon atoms but different structural configurations.</p> Signup and view all the answers

    What is the classification of isomers based on their spatial arrangement?

    <p>They are classified into optical isomers or stereo-isomers.</p> Signup and view all the answers

    What is the characteristic of monosaccharides in terms of ring structure?

    <p>They form hemiacetals and hemiketals.</p> Signup and view all the answers

    What is the classification of ribose and ribulose?

    <p>5-carbon monosaccharides</p> Signup and view all the answers

    What is the common characteristic of all monosaccharides?

    <p>They are the basic unit of carbohydrates.</p> Signup and view all the answers

    What is the shape of the 6-membered ring formed by aldohexoses in solution?

    <p>Chair formation</p> Signup and view all the answers

    What is the primary function of carbohydrates in living organisms?

    <p>Carbohydrates are essential components of all living organisms, serving as energy sources and structural components.</p> Signup and view all the answers

    What distinguishing feature sets carbohydrates apart from other biomolecules?

    <p>Carbohydrates contain an aldehyde (-CHO) or ketone (-C=O) group with two or more hydroxyl (-OH) groups in their structures.</p> Signup and view all the answers

    How do monosaccharides, disaccharides, oligosaccharides, and polysaccharides differ in terms of their structural composition?

    <p>They differ in the number of monomeric units present, with monosaccharides being the simplest and polysaccharides being the most complex.</p> Signup and view all the answers

    What is the significance of carbohydrates in the human body, and why can't we do away with them?

    <p>Carbohydrates are essential for energy production and provide structural components for cells and tissues, making them indispensable for human health.</p> Signup and view all the answers

    What are some examples of simple and complex carbohydrates?

    <p>Simple carbohydrates include glyceraldehyde, dihydroxyacetone, glucose, and fructose, while complex carbohydrates include polysaccharides like starch and cellulose.</p> Signup and view all the answers

    How do aldoses and ketoses differ in terms of their structural composition?

    <p>Aldoses have an aldehyde (-CHO) group, while ketoses have a ketone (-C=O) group, which affects their reactivity and function in biological systems.</p> Signup and view all the answers

    What is the characteristic that defines monosaccharides, and how do they differ from other types of carbohydrates?

    <p>Monosaccharides are the simplest carbohydrates, consisting of a single sugar molecule, and are characterized by their ability to undergo hydrolysis.</p> Signup and view all the answers

    What is the importance of carbohydrates in maintaining the structure and function of cells and tissues?

    <p>Carbohydrates provide structural components, such as cell walls and connective tissue, and are essential for maintaining cellular function and integrity.</p> Signup and view all the answers

    All monosaccharides are aldoses.

    <p>False</p> Signup and view all the answers

    The classification of carbohydrates is based on the number of carbon atoms present in their structures.

    <p>True</p> Signup and view all the answers

    Aldoses and ketoses are structural isomers of each other.

    <p>True</p> Signup and view all the answers

    Carbohydrates are not essential components of all living organisms.

    <p>False</p> Signup and view all the answers

    Monosaccharides can be hydrolyzed into simpler forms of carbohydrates.

    <p>False</p> Signup and view all the answers

    Carbohydrates are only found in plants.

    <p>False</p> Signup and view all the answers

    Monosaccharides are classified based on the number of carbon atoms present in their structures.

    <p>True</p> Signup and view all the answers

    Aldoses and ketoses have the same structural composition.

    <p>False</p> Signup and view all the answers

    Monosaccharides are soluble in water.

    <p>True</p> Signup and view all the answers

    Ketoses are always 6-carbon monosaccharides.

    <p>False</p> Signup and view all the answers

    Carbohydrates are not important for the structure and function of cells and tissues.

    <p>False</p> Signup and view all the answers

    Carbohydrates are not essential for human life.

    <p>False</p> Signup and view all the answers

    Glucose is an example of a disaccharide.

    <p>False</p> Signup and view all the answers

    Carbohydrates can be classified as simple and complex carbohydrates.

    <p>True</p> Signup and view all the answers

    Carbohydrates are not essential for the human body and can be eliminated from the diet.

    <p>False</p> Signup and view all the answers

    All carbohydrates have a similar structure.

    <p>False</p> Signup and view all the answers

    All monosaccharides contain 1 or more asymmetric carbons.

    <p>False</p> Signup and view all the answers

    D-Glucose and D-mannose are epimers at C-2 and C-4.

    <p>False</p> Signup and view all the answers

    Anomers are a type of diastereoisomer.

    <p>True</p> Signup and view all the answers

    The presence of asymmetric carbons influences the optical activity of compounds.

    <p>True</p> Signup and view all the answers

    D-Galactose and D-mannose are epimers.

    <p>False</p> Signup and view all the answers

    The C-1 in a ring structure can become the asymmetric centre of the ring.

    <p>True</p> Signup and view all the answers

    Epimers are a type of enantiomer.

    <p>False</p> Signup and view all the answers

    Stereoisomers have the same structural formula but differ in spatial configuration.

    <p>True</p> Signup and view all the answers

    Study Notes

    Monosaccharides

    • Monosaccharides are the basic unit of carbohydrates, water-soluble white crystalline solids with a sweet taste.
    • They cannot be hydrolyzed into a simpler form of carbohydrates as they are already in simplest form.
    • Examples include glucose, fructose, galactose, ribose (in RNA), and Deoxyribose (in DNA).

    Classification of Monosaccharides

    • Based on the number of carbon atoms present in their structures:
      • Trioses: 3-carbon monosaccharides
      • Tetroses: 4-carbon monosaccharides
      • Pentoses: 5-carbon monosaccharides (e.g., ribose and ribulose, xylose and xylulose)
      • Hexoses: 6-carbon monosaccharides
      • Heptoses: 7-carbon monosaccharides

    Structural Isomerism

    • Aldose and ketose sugars are structural isomers, having the same number and kinds of atoms, but different structural or spatial configurations.
    • Examples include erythrose (aldose) and erythulose (ketose), which are 4-carbon monosaccharides.

    Ring Structure

    • Glucose and fructose do not exist in open-chain structures, but cyclize into rings, forming hemiacetals and hemiketals.
    • Hexoses form when the second to last –OH group reacts with a C=O.
    • Aldohexoses form 6-membered rings, and ketohexoses and aldopentoses form 5-membered rings.

    Haworth Structures

    • The 6-membered ring is not planar but rather exists in the chair formation.
    • Haworth structures show the ring structure of sugars.

    Stereoisomers

    • Stereoisomers are molecules with the same structural formula but with different spatial configuration.
    • Types of stereoisomers:
      • Enantiomers: have four different atoms or groups of atoms attached.
      • Epimers: isomers that differ due to the H and OH configuration of carbons 2 or 3 or 4.
      • Diastereoisomers: have a different spatial configuration, but are not enantiomers or epimers.
      • Anomers: have an additional asymmetric carbon added after cyclization.

    Optical Isomerism

    • The presence of asymmetric carbons or chirality influences the optical activity of compounds.
    • Examples include aldose and ketose sugars, which have different optical activity due to the presence of asymmetric carbons.

    Carbohydrates

    • Carbohydrates are essential components of all living organisms, including humans, plants, animals, bacteria, and viruses.
    • They contain an aldehyde (-CHO) or ketone (-C=O) group with two or more hydroxyl (-OH) groups in their structures.

    Monosaccharides

    • Monosaccharides are the basic units of carbohydrates.
    • They are water-soluble white crystalline solids with a sweet taste.
    • Examples include glucose, fructose, galactose, ribose (in RNA), and deoxyribose (in DNA).
    • They cannot be hydrolyzed into a simpler form of carbohydrates as they are already in their simplest form.

    Classification of Monosaccharides

    • Classified based on the number of carbon atoms in their structures:
      • Trioses: 3-carbon monosaccharides
      • Tetroses: 4-carbon monosaccharides
      • Pentoses: 5-carbon monosaccharides
      • Hexoses: 6-carbon monosaccharides
      • Heptoses: 7-carbon monosaccharides

    Isomerism in Monosaccharides

    • Ketoses are isomers of aldoses, with the same number and kinds of atoms but different structural or spatial configurations.
    • Isomers of carbohydrates can be classified into two classes:
      • Structural isomers
      • Optical isomers (stereo-isomers)

    Structural Isomerism

    • Commonly seen differences are on carbons 1 and 2, with no variation in spatial arrangement.
    • Examples include erythrose (aldose) and erythulose (ketose), which are 4-carbon monosaccharides.

    Ring Structure of Carbohydrates

    • In solution, glucose and fructose do not exist in open-chain structures, but rather cyclize into rings, forming hemiacetals and hemiketals.
    • Hexoses form when the second to last –OH group reacts with a C=O.
    • Aldohexoses form 6-membered rings, and ketohexoses and aldopentoses form 5-membered rings.

    Haworth Structures

    • Haworth showed that glucose and fructose cyclize into rings, forming hemiacetals and hemiketals.
    • The 6-membered ring is not planar, but rather exists in the chair formation.

    Stereoisomerism

    • Same structural formula but with different spatial configuration.
    • Enantiomers – four different atoms or groups of atoms are attached.

    Assessment Details

    • Practical Assess: Practicals 1 to 8 (10%)
    • Make-up Assessment Dates: To be announced
    • Practical report Submissions (15%)
    • Tutorial Quiz Submissions (5%)
    • Main Exam (3 hours): Date to be advised
    • Supplementary Exam (3 hours): Date to be advised

    Introduction to Carbohydrates

    • Carbohydrates are essential components of all living organisms
    • Carbohydrates contain an aldehyde (-CHO) or ketone (-C=O) group with two or more hydroxyl (-OH) groups in their structures
    • Examples include: Glyceraldehyde, Dihydroxyacetone, Glucose, Fructose

    Classification of Carbohydrates

    • General classification: monosaccharides, disaccharides, oligosaccharides, polysaccharides, based on the number of monomeric units present

    Monosaccharides

    • Monosaccharides are the basic unit of carbohydrates
    • They are water-soluble white crystalline solids with a sweet taste
    • Examples include: glucose, fructose, galactose, ribose (in RNA), Deoxyribose (in DNA)
    • They cannot be hydrolyzed into a simpler form of carbohydrates as they are already in simplest form

    Classification of Monosaccharides

    • Trioses: 3-carbon monosaccharides
    • Tetroses: 4-carbon monosaccharides
    • Pentoses: 5-carbon monosaccharides
    • Hexoses: 6-carbon monosaccharides
    • Heptoses: 7-carbon monosaccharides

    Isomerism in Monosaccharides

    • Ketoses are isomers of aldoses, i.e. same number and kinds of atoms, but different structural or spatial configurations
    • Isomers of carbohydrates are classified into two different classes:
      • Structural isomers
      • Optical isomers or stereo-isomers

    Enantiomers: D and L Configurations

    • D (dextro) and L (levo) of glyceraldehyde contain a single asymmetric carbon – and are mirror images
    • Enantiomers have the same structural formula but with different spatial configuration

    Epimers

    • Epimers – isomers that differ due to the H and OH configuration of carbons 2 or 3 or 4
    • Examples include: D-glucose and D-mannose are epimers at C-2, and D-glucose and D-galactose are epimers at C-4

    Diastereoisomers

    • D-Glucose and D-mannose are epimers at C-2, and D-glucose and D-galactose are epimers at C-4
    • Note: there is no epimeric relationship between D-galactose and D-mannose, their differences are at more than 1 carbon (i.e. 2 and 4); hence they are diastereoisomers – (neither epimers, nor enantiomers)

    Anomers

    • Anomers - Following cyclisation, there is an additional asymmetric carbon added
    • The C-1 in a ring structure can become the asymmetric centre of the ring, resulting in the alpha- and beta-configurations of the sugar

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