Chemistry of Carbohydrates Lecture 7
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Questions and Answers

What is the general formula for carbohydrates?

  • CnH2nOn
  • CnH2n+2On
  • C(H2O)n
  • Cn(H2O)n (correct)
  • Which of the following is NOT a monosaccharide?

  • Sucrose (correct)
  • Galactose
  • Glucose
  • Fructose
  • Which monosaccharide is a component of RNA and DNA?

  • Ribose (correct)
  • Fructose
  • Galactose
  • Glucose
  • Which of the following is NOT a function of carbohydrates in the body?

    <p>Acting as hormones that regulate metabolism</p> Signup and view all the answers

    Which type of carbohydrate is considered the building block of all carbohydrates?

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

    Which of the following is a hexose sugar?

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

    Which of the following is a disaccharide?

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

    Which of the following statements is TRUE about monosaccharides?

    <p>They can exist as both linear and cyclic forms.</p> Signup and view all the answers

    What type of monosaccharides contains an aldehyde group?

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

    Which of the following is the mother compound of aldoses?

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

    Which disaccharide is not considered reducing?

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

    What is the general structure of ketoses characterized by?

    <p>A ketone group</p> Signup and view all the answers

    Oligosaccharides are defined as polymers of how many monosaccharide units?

    <p>3-10</p> Signup and view all the answers

    Which enzyme hydrolyzes lactose into glucose and galactose?

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

    Which type of polysaccharides are built from more than 10 monosaccharide units?

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

    Which example represents a ketose?

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

    Study Notes

    Carbohydrates

    • Carbohydrates are the most abundant organic molecules in nature, formed of carbon, hydrogen, and oxygen atoms with a ratio of 1:2:1 and the general formula Cn(H2O)n.
    • They are organic substances (polyhydroxy aldehyde or ketone) and most names for sugars end in -ose.

    Biomedical Importance of Carbohydrates

    • Carbohydrates are the chief source of energy for most organisms.
    • They act as a storage form of energy in the body.
    • They serve as cell membrane components that mediate some forms of intercellular communication.
    • Ribose and deoxyribose sugars form part of the structure of RNA and DNA.
    • Major antigens are carbohydrates in nature, e.g., blood group substances.

    Classification of Carbohydrates

    • Carbohydrates are classified according to the hydrolysis products (number of individual simple units) into:
      • Monosaccharides: contain 1 sugar unit (cannot be hydrolyzed), e.g., Glucose, galactose, mannose, and fructose.
      • Disaccharides: contain 2 sugar units, e.g., Maltose, lactose, and sucrose.
      • Oligosaccharides: contain 3-10 sugar units.
      • Polysaccharides: contain more than 10 sugar units, e.g., Starch, glycogen, and cellulose.

    Monosaccharides

    • Monosaccharides are the simplest units of carbohydrates and the building blocks.
    • The general formula is (CH2O)n, so the name of carbohydrates (carbon + H2O).
    • The ratio between carbon and H2O is 1.
    • Most monosaccharides occurring in mammals are D sugars.
    • Examples of monosaccharides include Glucose, mannose, galactose, and fructose.

    Classification of Monosaccharides

    • Classification based on the number of carbon atoms:
      • Trioses: contain 3 carbon atoms.
      • Tetroses: contain 4 carbon atoms.
      • Pentose: contain 5 carbon atoms.
      • Hexoses: contain 6 carbon atoms.
    • Classification based on the functional group:
      • Aldoses: monosaccharides containing an aldehyde group (-CH=O), e.g., Glyceraldehyde, erythrose, ribose, glucose, galactose, and mannose.
      • Ketoses: monosaccharides containing a ketone group (-C=O), e.g., Dihydroxyacetone, erythrulose, ribulose, and fructose.

    Disaccharides

    • Disaccharides consist of two monosaccharides united together by glycosidic linkage.
    • Disaccharides are classified into reducing disaccharides and non-reducing disaccharides.
    • Examples of disaccharides include:
      • Sucrose (non-reducing): hydrolyzed by sucrase enzyme into Glucose + Fructose.
      • Lactose (reducing): hydrolyzed by lactase enzyme into Galactose + Glucose.
      • Maltose (reducing): hydrolyzed by maltase enzyme into 2 Glucose.

    Oligosaccharides and Polysaccharides

    • Oligosaccharides are polymers of 3-10 monosaccharide units and are not an important source of carbohydrates in the diet for humans.
    • Polysaccharides are composed of more than 10 monosaccharide units linked by glycosidic bonds and are non-reducing.
    • Examples of polysaccharides include Starch, glycogen, and cellulose.

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    Description

    This quiz covers the chemistry of carbohydrates, including their structure, composition, and properties. It's based on Lecture 7 by Dr. Wael Sobhy Darwish, a Biochemistry PhD.

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