Carbohydrates in Biochemistry
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Questions and Answers

What is the general formula for carbohydrates?

  • C(H2O)n (correct)
  • CHnO
  • CH2O
  • Cn(H2O)n

    • What is the role of carbohydrates in plants?

  • They are responsible for photosynthesis
  • They provide structure to the plant cell wall (correct)
  • They are a source of energy for the plant
  • They help the plant to respond to stimuli

    • What is another name for carbohydrates?

  • Hydrocarbons
  • Polymers
  • Saccharides (correct)
  • Polysaccharides

    • What is the function of carbohydrates in the human body?

    <p>They are a source of energy</p> Signup and view all the answers

    What type of carbohydrate contains two monosaccharide units?

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

    What is the term for carbohydrates that contain 3-9 monosaccharide units?

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

    What is the minimum number of monosaccharide units a polysaccharide can contain?

    <p>More than 9</p> Signup and view all the answers

    Which type of sugar contains a free aldehyde or ketose group?

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

    What is the purpose of Molisch's test?

    <p>To detect the presence of carbohydrates</p> Signup and view all the answers

    What is the principle behind Benedict's test?

    <p>Reduction of cupric ion in an alkaline medium</p> Signup and view all the answers

    What is the purpose of Barfoed's test?

    <p>To distinguish between mono- and disaccharides</p> Signup and view all the answers

    What is the purpose of Seliwanoff's test?

    <p>To distinguish between ketoses and aldoses</p> Signup and view all the answers

    Which of the following is an example of a non-reducing sugar?

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

    What is the common characteristic of all monosaccharides?

    <p>They are reducing sugars</p> Signup and view all the answers

    Study Notes

    Carbohydrates

    • Organic molecules containing carbon, hydrogen, and oxygen
    • Formed by green plants during photosynthesis from CO2 and water
    • General formula: C(H2O)n, meaning "watered carbon"
    • Also known as "saccharide" or sugars
    • Major source of energy from diet

    Importance of Carbohydrates

    • Widely distributed in nature
    • Key intermediates of metabolism (sugars)
    • Structural components of plants (cellulose)
    • Central to industrial products (paper, fibers)
    • Key component of food sources (sugars, flour, vegetable fiber)

    Classification of Carbohydrates

    • Simple sugars (monosaccharides): contain one unit (e.g., glucose, fructose)
    • Complex sugars:
      • Disaccharides: contain two units (e.g., sucrose, lactose, maltose)
      • Oligosaccharides: contain 3-9 units (e.g., raffinose)
      • Polysaccharides: contain more than 9 units (e.g., starch)

    Reducing and Non-Reducing Sugars

    • Reducing sugars: have free aldehyde or ketose group (e.g., glucose, galactose, fructose, lactose, maltose)
    • Non-reducing sugars: lack free aldehyde or ketose group (e.g., sucrose, oligosaccharides, polysaccharides)

    Tests for Carbohydrates

    Molisch's Test

    • General test for all carbohydrates
    • Principle: dehydration of carbohydrates into furfural compounds in strong acid, reacting with α-naphthol to form a violet-colored ring
    • Procedure: 1 ml sugar, 5 drops α-naphthol, 10 drops H2SO4 slowly

    Benedict's Test

    • Test for reducing sugars
    • Principle: reduction of cupric ion into cuprous oxide in hot alkaline medium, causing color change and red precipitate formation
    • Procedure: 0.5 ml sugar solution, 1 ml Benedict's reagent, boiling water bath for 3 minutes

    Barfoed's Test

    • Distinguishes mono from disaccharides
    • Principle: reduction of cupric ion in Barfoed's reagent faster by monosaccharides than disaccharides in hot acidic medium
    • Procedure: 1 ml sugar solution, 1 ml Barfoed's reagent, boiling water bath for 2-3 minutes

    Seliwanoff's Test

    • Distinguishes between ketoses and aldoses
    • Principle: ketoses are more rapidly dehydrated than aldoses when heated
    • Used to identify ketoses and aldoses

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    Description

    Learn about carbohydrates, their definition, formation, and importance. Explore their structure, function, and role as a major source of energy.

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