Carbohydrate Chemistry Overview
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Questions and Answers

What does the hydrolysis of sucrose by dilute acids or sucrase yield?

  • Glucose and sucrose
  • Galactose and lactose
  • Fructose and galactose
  • Glucose and fructose (correct)

    • Which of the following is a characteristic of lactose?

  • It contains a ẞ-(1,4) galactosidic linkage (correct)
  • It can reduce Fehling and Benedict solutions (correct)
  • It does not have a free aldehyde group
  • It is highly fermentable by yeast

    • Why is lactose considered a perfect sugar for babies?

  • It induces gas formation
  • It is easily fermented in the stomach
  • It is a natural source of galactose (correct)
  • It has a high sweetness level

    • Maltose is formed by which type of linkage between two molecules of glucose?

    <p>α-1,4 glucosidic linkage</p> Signup and view all the answers

    Which property is true for maltose?

    <p>It has a free carbonyl group</p> Signup and view all the answers

    Which monosaccharide is a pentose and classified as an aldose?

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

    What is the main blood sugar that tissues utilize?

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

    Which compound has no asymmetric carbon atom?

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

    Which disaccharide is formed from galactose and glucose?

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

    What are carbohydrates primarily composed of?

    <p>Carbon, hydrogen, and oxygen</p> Signup and view all the answers

    Which of the following is a characteristic of monosaccharides?

    <p>They cannot be further hydrolyzed</p> Signup and view all the answers

    Which of the following statements about ketoses is true?

    <p>They have less asymmetric carbon atoms than aldoses.</p> Signup and view all the answers

    What is the primary storage form of energy in animals?

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

    Which hexose is classified as a keto sugar?

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

    Which type of carbohydrate has a rapid rise in blood sugar levels?

    <p>Simple carbohydrates</p> Signup and view all the answers

    What type of isomers differ in spatial configuration of atoms but have the same molecular formula?

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

    How many optical isomers does a hexose with 4 asymmetric carbon atoms have?

    <p>8</p> Signup and view all the answers

    What is the general formula for many simple carbohydrates?

    <p>[CH2O]n</p> Signup and view all the answers

    Which of the following best describes oligosaccharides?

    <p>Carbohydrates with 3-10 sugar units</p> Signup and view all the answers

    What is a function of carbohydrates in the human body?

    <p>Serving as structural components</p> Signup and view all the answers

    Which monosaccharide corresponds to the classification for 5 carbon atoms?

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

    What distinguishes D isomers from L isomers in sugars?

    <p>L isomers have the OH group on the left side.</p> Signup and view all the answers

    Which statement correctly describes epimerism?

    <p>Epimers differ in configuration around only one carbon atom.</p> Signup and view all the answers

    What is an anomer?

    <p>Isomers that differ around the anomeric carbon after cyclization.</p> Signup and view all the answers

    Which of the following explains mutarotation?

    <p>It is the spontaneous change of the optical rotation angle in sugar solutions.</p> Signup and view all the answers

    What happens in a racemic mixture?

    <p>The activities of its isomers cancel each other out.</p> Signup and view all the answers

    How do monosaccharides behave in water?

    <p>They are all soluble in water.</p> Signup and view all the answers

    What defines an asymmetric carbon atom?

    <p>A carbon atom bonded to four different groups.</p> Signup and view all the answers

    What is the specific rotation of freshly dissolved β-glucose?

    <p>+19 degrees</p> Signup and view all the answers

    What products are formed as a result of alcoholic fermentation?

    <p>Ethyl alcohol and carbon dioxide</p> Signup and view all the answers

    Which of the following is formed by the oxidation of glucose?

    <p>Glucuronic acid</p> Signup and view all the answers

    What is a key characteristic of disaccharides?

    <p>They are glycosides formed by the condensation of two monosaccharides.</p> Signup and view all the answers

    Which of the following statements is true regarding sucrose?

    <p>It is a glycosidic linkage of glucose and fructose.</p> Signup and view all the answers

    What type of sugar is derived from the reduction of sugars?

    <p>Sugar alcohols</p> Signup and view all the answers

    Which type of disaccharide is maltose?

    <p>Reducing sugar</p> Signup and view all the answers

    What happens during the reduction of a carbonyl group?

    <p>It forms a corresponding alcohol.</p> Signup and view all the answers

    Which type of acids are formed from the oxidation of aldo-sugars?

    <p>Aldonic or Aldaric acids</p> Signup and view all the answers

    Study Notes

    Carbohydrate Chemistry

    • Carbohydrates are polyhydroxyaldehydes or ketones
    • They are classified into monosaccharides, oligosaccharides, and polysaccharides
    • They are held together by glycosidic bonds
    • They provide energy and serve as structural components

    Carbohydrate Properties

    • Chemically, carbohydrates contain carbon, hydrogen, and oxygen
    • The general formula is [CH₂O]n (mostly hydrate of carbon as the ratio of hydrogen to oxygen 2:1) where n is the number of carbon atoms, typically 3 to 8
    • Carbohydrates are found in grains, vegetables, fruits, milk, and other dairy products
    • The term "sugar" is used for carbohydrates that are soluble in water and sweet to taste
    • Some carbohydrates are not digestible
    • Carbohydrates are a primary energy source (4 kcal/g)
    • Storage forms include glycogen in animals and starch in plants
    • Structural components include glycosaminoglycans and cellulose

    Classification of Carbohydrates

    • Monosaccharides: one sugar unit
    • Disaccharides: two sugar units
    • Oligosaccharides: 3-10 sugar units
    • Polysaccharides: more than 10 sugar units

    Monosaccharides

    • Cannot be further hydrolyzed
    • Contain one sugar unit
    • Building blocks of all carbohydrates
    • Classified according to the number of carbon atoms: Trioses, Tetroses, Pentoses, Hexoses, Heptoses, Nanoses
    • Further classified by functional groups: Aldoses (aldehyde group) and Ketoses (ketone group)
    • Examples: Glucose, Fructose, Galactose, Ribose, etc.

    Monosaccharides: Types

    • Aldoses:

      • Glyceraldehyde
      • Erythrose
      • Ribose
      • Xylose
      • Arabinose
      • Glucose
      • Galactose
      • Mannose

    • Ketoses:

      • Dihydroxyacetone
      • Erythrulose
      • Ribulose
      • Xylulose
      • Fructose

    Biochemical and Biological Importance of Some Hexoses

    • Glucose: Sugar of grape; main blood sugar; principle sugar used by tissues
    • Fructose: Found in fruits, honey; sugar of fetal blood; principle sugar of semen
    • Galactose: Found in combination with glucose in milk sugar (Lactose); present in tissues as galactolipid and glycoprotein

    Isomers

    • Compounds with the same molecular formula but different structures
    • Constitutional isomers: Differ in functional group arrangement
    • Stereoisomers: Differ in spatial arrangement of atoms
      • Diastereomers: Non-mirror image isomers
        • Epimers: Differ in configuration around only one carbon atom (excluding the carbonyl carbon)
        • Anomers: Differ in configuration around the carbonyl carbon after cyclization
      • Enantiomers: Mirror image isomers
        • Optical isomers: Different spatial arrangements affect the rotation of polarized light

    Optical Isomerism

    • D isomers: OH group on the right side of the penultimate carbon (majority of sugars in humans)
    • L isomers: OH group on the left side of the penultimate carbon

    Diastereomers of Monosaccharides

    • C2-Epimer of Glucose: Mannose
    • C4-Epimer of Glucose: Galactose

    Cyclic Structure of Monosaccharides

    • Monosaccharides in solution exist primarily as cyclic structures
    • Cyclization creates a new asymmetric carbon atom (anomeric carbon)
    • Glucose forms a six-membered ring; Fructose forms a five-membered ring

    Mutarotation

    • Spontaneous change in the specific rotation of freshly prepared sugar solutions
    • Results from interconversion of α and β anomers
    • Equilibrium mixture typically has a specific rotation of +52.5° for glucose

    Chemical Properties of Monosaccharides

    • Reactions with concentrated acids (e.g., H₂SO₄), used for general carbohydrate tests
    • Esterification: Formation of esters, important example is phosphorylation (e.g., glucose-6-phosphate)
    • Oxidation: Oxidation of the last primary alcoholic group gives uronic acids (e.g., glucuronic acid).
    • Reduction: Reduction produces corresponding alcohols (e.g., sorbitol).
    • Reducing properties: Reduction of Fehling or Benedict reagent (used to detect glucose in urine)

    Disaccharides

    • Formed by condensation of two monosaccharides
    • Crystalline, water-soluble, and sweet
    • Classified by presence/absence of free reducing groups (aldehyde or ketone)
    • Examples: Sucrose, Lactose, and Maltose

    Sucrose

    • Cane/beet sugar
    • Formed by condensation of a-D-glucose and β-D-fructose
    • Does not contain free reducing groups
    • Does not reduce Fehling or Benedict solutions
    • Does not undergo mutarotation

    Lactose

    • Milk sugar
    • Formed by condensation of β-D-galactose and a-D-glucose
    • Contains free aldehyde group (from glucose) and reduces Fehling/Benedict reagents
    • Non-fermentable by yeast

    Maltose

    • Formed by condensation of two a-D-glucose units
    • Contains free aldehyde group (from glucose) and reduces Fehling/Benedict reagents

    Isomaltose

    • Formed by hydrolysis of starch and glycogen
    • a-1, 6-glucosidic linkage

    Derived Sugars

    • Monosaccharides with unusual structures or not represented by the general formula
    • Acid sugars: (by oxidation of sugars)
    • Sugar alcohols: (by reduction of sugars)
    • Deoxy sugars: (e.g., deoxyribose in DNA)
    • Amino sugars: (e.g., glucosamine, galactosamine)
    • Glycosides

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    Carbohydrate Chemistry Lecture 1 PDF

    Description

    This quiz covers the fundamental aspects of carbohydrate chemistry, including their classification, properties, and structural roles. Learn about monosaccharides, oligosaccharides, and polysaccharides, as well as their chemical composition and significance as energy sources. Test your understanding of how carbohydrates function in biological systems.

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