Unit 4 - Biological molecules
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Questions and Answers

What color change indicates a positive test for starch when iodine solution is added?

  • Orange-brown to blue-black (correct)
  • Clear to red
  • Yellow to green
  • Blue to teal
  • Which of the following correctly describes a positive test for protein using Biuret solution?

  • Change from blue to violet/purple (correct)
  • Change from brown to blue
  • Change from red to green
  • Change from yellow to clear
  • In a test for lipids, what is observed to confirm a positive result?

  • Formation of a cloudy emulsion (correct)
  • Outgrowth of particles
  • Change of color to pink
  • Formation of a clear solution
  • Which bases pair correctly in DNA structure?

    <p>Adenine with Thymine (D)</p> Signup and view all the answers

    What structure forms the 'backbone' of a DNA molecule?

    <p>Phosphate and deoxyribose sugar (D)</p> Signup and view all the answers

    What are the primary chemical elements found in carbohydrates?

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

    What is a disaccharide formed from two glucose molecules?

    <p>Maltose (B)</p> Signup and view all the answers

    Which type of lipid is typically solid at room temperature?

    <p>Fats (B)</p> Signup and view all the answers

    What are proteins primarily composed of?

    <p>Amino acids (A)</p> Signup and view all the answers

    What is the role of Benedict's solution in food testing?

    <p>To test for glucose (C)</p> Signup and view all the answers

    What color change indicates a positive test for glucose using Benedict's solution?

    <p>Blue to orange or brick red (A)</p> Signup and view all the answers

    How many different amino acids are commonly found in proteins?

    <p>20 (D)</p> Signup and view all the answers

    Which molecule serves as the basic unit of triglycerides?

    <p>Glycerol (D)</p> Signup and view all the answers

    Flashcards

    Carbohydrates

    Organic molecules containing carbon, hydrogen, and oxygen. They are long chains of simple sugars.

    Glucose

    A simple sugar, the basic building block of carbohydrates.

    Maltose

    A type of carbohydrate formed when two glucose molecules join together.

    Polysaccharides

    Large complex carbohydrates made up of many glucose molecules joined together. Examples include starch, glycogen, and cellulose.

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    Proteins

    Organic molecules that contain carbon, hydrogen, oxygen, and nitrogen. They are long chains of amino acids.

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    Fats (Lipids)

    Organic molecules containing carbon, hydrogen, and oxygen. They are made up of glycerol and three fatty acid chains.

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    Glycerol

    A single molecule in fats that is attached to three fatty acid chains.

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    Benedict's Test

    A test that uses Benedict's solution to detect the presence of reducing sugars, like glucose. A positive test results in a color change from blue to orange or brick red.

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    Iodine Test

    A chemical test that uses iodine solution to detect the presence of starch in a sample. A positive result is indicated by a color change from orange-brown to blue-black.

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    Biuret Test

    A chemical test that uses Biuret solution to detect the presence of protein in a sample. A positive result is indicated by a color change from blue to violet/purple.

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    Ethanol Test for Lipids

    A chemical test that uses ethanol to detect the presence of lipids (fats and oils) in a sample. A positive result is indicated by a cloudy emulsion forming when the ethanol is added to water.

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    DCPIP Test for Vitamin C

    A chemical test that uses DCPIP solution to detect the presence of Vitamin C in a sample. A positive result is indicated by the blue color of the dye disappearing.

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    DNA

    The molecule that contains the genetic instructions for the growth and development of all organisms. It has a double helix structure, consisting of two strands of nucleotides wound around each other.

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    Study Notes

    Biological Molecules

    • Biological molecules—carbohydrates, proteins, and lipids—are the building blocks of life.
    • They all contain carbon, making them organic molecules.

    Chemical Elements

    • Carbohydrates: Contain carbon, oxygen, and hydrogen.
    • Proteins: Contain carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur.
    • Lipids: Contain carbon, oxygen, and hydrogen.

    Carbohydrates: Large Molecules from Smaller

    • Carbohydrates are long chains of simple sugars.
    • Glucose is a simple sugar (monosaccharide).
    • Two glucose molecules form maltose (disaccharide).
    • Many glucose molecules form starch, glycogen, or cellulose (polysaccharides).

    Fats (Lipids)

    • Most fats in the body are triglycerides.
    • Triglycerides are composed of one glycerol molecule and three fatty acid chains.
    • Fatty acids vary in size and structure.
    • Lipids are categorized as solids (fats) or liquids (oils) at room temperature.

    Proteins

    • Proteins are long chains of amino acids.
    • There are about 20 different amino acids.
    • Amino acids have a similar basic structure but differ in their "R" group.
    • Amino acids link to form proteins.
    • The order of amino acids determines the protein's function.
    • A small change in amino acid order results in a different protein.

    Food Tests

    • Glucose (reducing sugars): Benedict's solution, heated to 60-70°C, changes color from blue to orange/brick red if glucose is present.
    • Starch: Iodine solution changes color from orange-brown to blue-black in the presence of starch.
    • Proteins: Biuret solution changes color from blue to violet/purple in the presence of protein.
    • Lipids: A food sample mixed with ethanol, then water, forms a cloudy emulsion if lipids are present.
    • Vitamin C: DCPIP solution loses its blue color in the presence of Vitamin C.

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    Biological Molecules PDF

    Description

    Explore the foundational building blocks of life through this quiz on biological molecules, covering carbohydrates, proteins, and lipids. Learn how these organic molecules are structured and their essential roles in living organisms. Test your understanding of their components and classifications.

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