Lab 2: Biological Molecules
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Questions and Answers

What is the term used to describe the four classes of biological molecules?

  • Organomolecules
  • Micromolecules
  • Macromolecules
  • Biomolecules (correct)

    • Which type of molecules are composed of nucleotides?

  • Proteins
  • Lipids
  • Nucleic acids (correct)
  • Carbohydrates

    • What is the purpose of the Benedict's Test?

  • To detect the presence of lipids
  • To detect the presence of nucleic acids
  • To detect the presence of proteins
  • To detect the presence of reducing sugars (correct)

    • What is the result of the reaction between cupric ions and certain sugars in the Benedict's Test?

    <p>The formation of an insoluble reddish precipitate</p> Signup and view all the answers

    What are the main components of lipids?

    <p>Fatty acids and glycerol</p> Signup and view all the answers

    What is the term used to describe the building blocks of carbohydrates?

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

    Which of the following is an example of a nucleic acid?

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

    What is the color of the Benedict's solution?

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

    What is the result of heating the Benedict's solution with certain sugars?

    <p>The solution changes from blue to green to reddish brown</p> Signup and view all the answers

    What is the primary source of carbohydrate in our diets?

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

    What is the result of a positive starch test?

    <p>A bluish-black color</p> Signup and view all the answers

    What is the function of copper sulfate in the Biuret reagent?

    <p>To react with peptide bonds</p> Signup and view all the answers

    What is the minimum number of linked amino acids required for a positive Biuret test?

    <p>4</p> Signup and view all the answers

    What is the result of a negative Biuret test?

    <p>A blue color</p> Signup and view all the answers

    What is the purpose of the Sudan IV test?

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

    What is the characteristic of lipids in an aqueous solution?

    <p>They have a lower density than water</p> Signup and view all the answers

    What is the result of a positive Sudan IV test?

    <p>A dark red-orange color</p> Signup and view all the answers

    Why are positive and negative controls important in the Sudan IV test?

    <p>Because the test is the most challenging of the four</p> Signup and view all the answers

    What happens to the Sudan reagent in a solution with lipids?

    <p>It stains the oil droplets a darker red-orange color</p> Signup and view all the answers

    Lipids are made up of chains of amino acids.

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

    All carbohydrates are reducing sugars.

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

    Nucleic acids are composed of amino acids.

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

    Benedict's solution is colorless.

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

    A positive Benedict's test is indicated by a blue color.

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

    Copper (I) oxide is formed when cupric ions react with certain sugars.

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

    Macromolecules have the same structure and function in the body.

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

    Glycerol is a type of carbohydrate.

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

    A reddish precipitate of copper (I) oxide is formed when cuprous ions react with certain sugars.

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

    Disaccharides always react with Benedict's reagent.

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

    Starch is a type of protein.

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

    Iodine is used to detect the presence of protein.

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

    Biuret reagent reacts with peptide bonds to produce a yellowish-brown color.

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

    Free amino acids will react with Biuret reagent.

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

    Sudan IV is soluble in water.

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

    A negative Sudan IV test result is indicated by a slightly darker red-orange color.

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

    Lipids have a higher density than water.

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

    A positive control is not necessary in the Sudan IV test.

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

    The iodine test is used to detect the presence of protein in a solution.

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

    Study Notes

    Biological Molecules

    • Living organisms are composed of molecules with diverse shapes and forms.
    • The four main classes of biological molecules are carbohydrates, proteins, lipids, and nucleic acids.

    Carbohydrates

    • Complex carbohydrates are made up of monosaccharides.
    • Some sugars, known as reducing sugars, contain free aldehyde or ketone groups.
    • Reducing sugars can be detected using Benedict's Test.

    Benedict's Test

    • Benedict's solution is blue and contains cupric ions.
    • When heated, cupric ions react with certain sugars, forming an insoluble reddish precipitate of copper (I) oxide.
    • The solution changes color from blue to green to reddish brown depending on the amount of sugar present.

    Starch

    • Starch is a polysaccharide produced by plants to store sugars for later energy needs.
    • Starch is a primary source of carbohydrate in our diets.
    • Starch interacts with iodine to produce a bluish-black color.

    Proteins

    • Proteins are made up of chains of amino acids.
    • Biuret reagent is used to test for the presence of protein.
    • Biuret reagent contains copper sulfate, which reacts with peptide bonds, resulting in a violet/lavender color.
    • Only proteins with four to six linked amino acids will react with Biuret reagent.

    Lipids

    • Lipids vary in composition, but main components include fatty acids and glycerol.
    • Sudan IV test is used to detect the presence of lipids.
    • Sudan IV is not soluble in water but is soluble in lipids.
    • If lipids are present, the Sudan reagent will stain the oil droplets a slightly darker red-orange color.

    Biological Molecules

    • Living organisms are composed of molecules with diverse shapes and forms.
    • The four main classes of biological molecules are carbohydrates, proteins, lipids, and nucleic acids.

    Carbohydrates

    • Complex carbohydrates are made up of monosaccharides.
    • Some sugars, known as reducing sugars, contain free aldehyde or ketone groups.
    • Reducing sugars can be detected using Benedict's Test.

    Benedict's Test

    • Benedict's solution is blue and contains cupric ions.
    • When heated, cupric ions react with certain sugars, forming an insoluble reddish precipitate of copper (I) oxide.
    • The solution changes color from blue to green to reddish brown depending on the amount of sugar present.

    Starch

    • Starch is a polysaccharide produced by plants to store sugars for later energy needs.
    • Starch is a primary source of carbohydrate in our diets.
    • Starch interacts with iodine to produce a bluish-black color.

    Proteins

    • Proteins are made up of chains of amino acids.
    • Biuret reagent is used to test for the presence of protein.
    • Biuret reagent contains copper sulfate, which reacts with peptide bonds, resulting in a violet/lavender color.
    • Only proteins with four to six linked amino acids will react with Biuret reagent.

    Lipids

    • Lipids vary in composition, but main components include fatty acids and glycerol.
    • Sudan IV test is used to detect the presence of lipids.
    • Sudan IV is not soluble in water but is soluble in lipids.
    • If lipids are present, the Sudan reagent will stain the oil droplets a slightly darker red-orange color.

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    Description

    This quiz covers the four major classes of biological molecules, including carbohydrates, proteins, lipids, and nucleic acids, and their building blocks.

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