Chemical Basis of Life Chapter 6
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Questions and Answers

What is the structural composition of a triglyceride?

  • 1 fatty acid linked to glycerol
  • 3 fatty acids linked to glycerol (correct)
  • 4 fatty acids linked to glycerol
  • 2 fatty acids linked to glycerol

    • Which characteristic is true of saturated fatty acids?

  • They are poorly packed together.
  • They have all single bonds between carbon atoms. (correct)
  • They are liquid at room temperature.
  • They contain double bonds between carbon atoms.

    • Why are triglyceride molecules not soluble in water?

  • They are polar molecules.
  • They have a high density.
  • They contain reactive groups.
  • They are non-polar molecules. (correct)

    • What is a common characteristic of animal triglycerides?

    <p>They are solid at room temperature.</p> Signup and view all the answers

    What is meant by the term 'ester linkage' in the context of triglycerides?

    <p>A bond formed between hydroxyl and carboxyl groups</p> Signup and view all the answers

    Which of the following is NOT a characteristic of lipids?

    <p>They readily form polymers.</p> Signup and view all the answers

    What is the primary building block of lipids?

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

    Which type of lipid functions in energy storage?

    <p>Fats and oils</p> Signup and view all the answers

    What defines a triglyceride?

    <p>1 glycerol plus 3 fatty acids</p> Signup and view all the answers

    What structural feature distinguishes saturated fatty acids from unsaturated fatty acids?

    <p>Presence of double bonds in hydrocarbon chains</p> Signup and view all the answers

    Which of the following lipids acts as a protective coating and water barrier?

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

    At room temperature, which type of lipid is typically solid?

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

    Which lipid type primarily serves regulatory functions such as hormones and vitamins?

    <p>Steroids and modified fatty acids</p> Signup and view all the answers

    What are the two types of nucleic acids?

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

    Which component is not part of a nucleotide?

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

    What is the main role of nucleic acids?

    <p>To store, transmit, and use genetic information</p> Signup and view all the answers

    What type of sugar is found in RNA?

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

    How are nucleotides connected in a nucleic acid?

    <p>By phosphodiester linkages</p> Signup and view all the answers

    Which part of a nucleotide specifies its identity in terms of functional groups?

    <p>Nitrogen-containing base</p> Signup and view all the answers

    In which direction do nucleic acids grow?

    <p>5′-to-3′ direction</p> Signup and view all the answers

    How many phosphate groups can a nucleotide contain?

    <p>One to three</p> Signup and view all the answers

    What is the primary difference between the sugars in DNA and RNA?

    <p>DNA contains deoxyribose while RNA contains ribose.</p> Signup and view all the answers

    What characteristic defines a fatty acid as polyunsaturated?

    <p>It has more than one double bond.</p> Signup and view all the answers

    Which of the following statements about RNA is correct?

    <p>RNA includes uracil instead of thymine.</p> Signup and view all the answers

    How do double bonds in fatty acids affect their physical state at room temperature?

    <p>They lead to fats being liquid due to low melting points.</p> Signup and view all the answers

    Why is starch more digestible than cellulose?

    <p>Starch is a branched polymer, while cellulose is a linear polymer.</p> Signup and view all the answers

    Which bases are classified as purines in RNA?

    <p>Adenine and Guanine</p> Signup and view all the answers

    What components make up a phospholipid?

    <p>Glycerol, 2 fatty acids, and a phosphate group.</p> Signup and view all the answers

    What is the role of the hydrophilic heads in phospholipids?

    <p>They attract water.</p> Signup and view all the answers

    What type of bonds hold the two strands of DNA together?

    <p>Hydrogen bonds</p> Signup and view all the answers

    Which of the following statements about steroids is true?

    <p>Some steroids function as signal molecules.</p> Signup and view all the answers

    Which statement about RNA structure is false?

    <p>RNA uses thymine as one of its bases.</p> Signup and view all the answers

    Which of the following elements is essential for life?

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

    What is one reason fats can provide energy when carbohydrates are depleted?

    <p>Fats are richer in energy compared to carbohydrates.</p> Signup and view all the answers

    Study Notes

    Lipids

    • Lipids are a diverse group of organic compounds including fats, oils, phospholipids, and cholesterol.
    • Composed primarily of carbon (C), hydrogen (H), and oxygen (O) with an H:O ratio greater than 2:1.
    • Building blocks of lipids are fatty acids and glycerol.
    • Lipids do not form polymers but consist of larger molecules made from smaller subunits.
    • Fats and oils function in energy storage; fats provide thermal insulation while waxes and oils serve as protective coatings.
    • Phospholipids compose cell membranes and are critical for cellular structure and recognition.
    • Carotenoids assist in light absorption during photosynthesis, and steroids regulate functions as hormones and vitamins.
    • Myelin, made of lipids, acts as electrical insulation around nerves.
    • Fats are solid at room temperature, whereas oils are liquid due to the structure of their fatty acids.

    Fatty Acid Structure

    • Consist of a long hydrocarbon chain and a polar carboxyl group (COOH).
    • Fatty acids can be saturated (no double bonds, solid at room temperature) or unsaturated (one or more double bonds, liquid at room temperature).
    • Polyunsaturated fatty acids have multiple double bonds, contributing to lower melting points.

    Triglycerides

    • Formed by three fatty acids linked to glycerol through ester linkages (dehydration synthesis).
    • Can consist of different types of fatty acids that do not need to be identical.
    • Non-polar nature makes triglycerides insoluble in water, leading to clumping in aqueous environments.

    Phospholipids

    • Comprised of glycerol, two fatty acids, and a phosphate group, giving rise to hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
    • Form bilayers in aqueous environments, crucial for cell membrane structure.

    Steroids

    • Signaling molecules that are integral to membrane structure and function.
    • Include hormones like testosterone and estrogen, regulating sexual development.
    • Cholesterol, produced in the liver, forms part of cell membranes and serves as a precursor for steroid hormones.

    Nucleic Acids (DNA and RNA)

    • Polymeric molecules responsible for genetic information storage, transmission, and usage.
    • Two types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), composed of nucleotides.
    • Nucleotides contain a pentose sugar, a phosphate group, and a nitrogenous base.
    • DNA contains deoxyribose; RNA contains ribose.

    Differences Between DNA and RNA

    • DNA bases: Adenine, Guanine, Cytosine, Thymine; RNA bases: Adenine, Guanine, Cytosine, Uracil.
    • DNA is double-stranded; RNA is single-stranded, lacking base-pairing.
    • Nucleotides in nucleic acids are linked by phosphodiester bond, growing in the 5' to 3' direction.

    Chemical Basis of Life

    • Life's essential elements are few and contribute to the same biological compounds across all living organisms.
    • The biochemical differences arise from unique atomic compositions and bonding in various compounds.
    • Both fats and carbohydrates serve as energy sources, with fats being more energy-dense.
    • Starch (branched polymer) is digestible while cellulose (linear polymer) is not, due to structural differences.

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    Description

    This quiz focuses on the chemical basis of life, specifically examining organic molecules like lipids and nucleic acids. It covers the structure and assembly of proteins, providing insight into their primary, secondary, tertiary, and quaternary structures. Test your understanding of these essential biological components.

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