Biomolecules II: Lipids
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Questions and Answers

Which of the following accurately describes a phospholipid?

  • Is not involved in cell membrane structure
  • Contains only one fatty acid molecule
  • Is entirely hydrophobic in nature
  • Has an X-group that can vary to determine the type (correct)

    • What components make up a basic phospholipid?

  • Three fatty acids and one sphingosine
  • One fatty acid, one glycerol, and one sugar
  • Two glycerol molecules and one fatty acid
  • Two fatty acids, one glycerol, one phosphate group, and one X-group (correct)

    • Which of the following is a characteristic of sphingolipids?

  • Does not have a phosphorus-containing group
  • Is present mainly in brain and nerve cell membranes (correct)
  • Only consists of fatty acids
  • Contains sphingosine linked to a fatty acid via an ester bond

    • What distinguishes a sphingophospholipid from other sphingolipids?

    <p>It has a ceramide backbone with a phosphoryl group</p> Signup and view all the answers

    What type of bond links the fatty acid to sphingosine in ceramides?

    <p>Amide bond</p> Signup and view all the answers

    Phosphatidylcholine can also be referred to as what?

    <p>A phospholipid with choline as the X-group</p> Signup and view all the answers

    Which class of lipids includes compounds that have both hydrophobic and hydrophilic properties?

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

    Which statement about X-groups in phospholipids is true?

    <p>They determine the specific type of phospholipid</p> Signup and view all the answers

    What type of sphingolipid is specifically associated with galactose?

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

    Which of the following best describes the character of waxes?

    <p>Water-repellant character</p> Signup and view all the answers

    Which component is NOT typically found in terpenes?

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

    What structural feature do complex derivatives of triterpenes possess?

    <p>Fused six-membered rings</p> Signup and view all the answers

    What is increased in rigidity for sphingolipids when the hydrocarbon chain length and saturation degree are higher?

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

    What does ω-3 signify in fatty acid nomenclature?

    <p>The first double bond is found three carbons from the methyl end.</p> Signup and view all the answers

    What is the main function of triacylglycerols in animals?

    <p>They serve as an energy reserve.</p> Signup and view all the answers

    How are double bonds in fatty acids typically configured?

    <p>Cis configuration and separated by a single methylene group.</p> Signup and view all the answers

    What type of reaction forms the ester bond in triacylglycerols?

    <p>Condensation reaction</p> Signup and view all the answers

    What are adipocytes primarily responsible for?

    <p>Synthesis and storage of triacylglycerols.</p> Signup and view all the answers

    Which of the following statements about fatty acid identification is true?

    <p>The position of double bonds is indicated by the Greek letter omega.</p> Signup and view all the answers

    Where in the body are adipose tissues primarily located?

    <p>At the subcutaneous layer and around main organs.</p> Signup and view all the answers

    What type of fatty acid is indicated by the abbreviation '16:0'?

    <p>A saturated fatty acid with 16 carbons and no double bonds.</p> Signup and view all the answers

    What is the major structural component of lipids?

    <p>Polar hydrophilic head and non-polar hydrophobic tail</p> Signup and view all the answers

    Which of the following classes of lipids are considered signaling molecules?

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

    What differentiates saturated fatty acids from unsaturated fatty acids?

    <p>Presence of one or more double bonds in the chain</p> Signup and view all the answers

    Which type of fatty acid has a hydrocarbon chain length greater than 22 carbons?

    <p>Very long-chain fatty acids (VLCFA)</p> Signup and view all the answers

    What structural feature do unsaturated fatty acids have that affects their melting point?

    <p>Kink or bend in the chain</p> Signup and view all the answers

    Which of the following statements is true regarding fatty acids?

    <p>Fatty acids can exist freely or attached to other molecules</p> Signup and view all the answers

    What is the primary function of lipids in the cell membrane?

    <p>Membrane structure and fluidity</p> Signup and view all the answers

    What type of lipid serves as a reservoir of energy within cells?

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

    Which type of fatty acid has a hydrocarbon chain length of less than 6 carbons?

    <p>Short-chain fatty acids (SCFA)</p> Signup and view all the answers

    Which class of lipids includes modified fatty acids like branched and cyclic forms?

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

    What is one function of cholesterol in the body?

    <p>Act as a precursor for steroid hormones</p> Signup and view all the answers

    Which type of lipoprotein has the highest percentage of protein?

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

    What is the primary function of bile acids?

    <p>Aid in lipid digestion</p> Signup and view all the answers

    Which of the following is NOT a family of steroid hormones?

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

    What distinguishes LDL from HDL lipoproteins in terms of function?

    <p>LDL transports lipids to tissues, HDL removes excess lipids</p> Signup and view all the answers

    What is cholesteryl ester?

    <p>An ester formed from cholesterol</p> Signup and view all the answers

    What is the density classification range for VLDL?

    <p>0.95–1.006 g/mL</p> Signup and view all the answers

    Which of the following is NOT associated with sterols in plants and fungi?

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

    Study Notes

    Biomolecules II: Lipids

    • Lipids are fats or lipo-
    • Not a polymer, insoluble in water but soluble in nonpolar solvents
    • Hydrophobic
    • Diverse structures and functions
    • General structure: polar hydrophilic head attached to nonpolar hydrophobic tails

    Topic Learning Outcomes

    • Identify lipids among other biomolecules
    • Differentiate between major lipid classes structurally (e.g., fatty acids, triacylglycerols, phospholipids, sphingolipids, waxes, isoprenoids, lipoproteins)
    • Relate lipid structure to function

    What is a Lipid?

    • Lipids are not a true polymer
    • Insoluble in water
    • Soluble in nonpolar solvents
    • Hydrocarbon chains often present
    • Various structures and functions
    • Polar hydrophilic head attached to nonpolar hydrophobic tail

    Functions of Lipids

    • Membrane components
    • Intracellular energy reservoir
    • Insulator
    • Protects surfaces
    • Specialized functions, including:
      • Steroid hormones
      • Eicosanoids (signalling molecules)
      • Gangliosides (modulators in cell signal transduction)

    Classes of Lipids

    • Triacylglycerols
    • Sphingolipids
    • Terpenes and steroids

    Fatty Acids

    • Carboxylic acids with a long hydrocarbon side chain
    • Differ from each other by:
      • Position of double bonds in the hydrocarbon chain
      • Branched or cyclic structures
    • Exist freely or attached to other molecules.
    • Saturated vs Unsaturated:
    • Saturated - only single bonds. High melting point, solid at room temperature.
    • Unsaturated - one or more double bonds. Lower melting point, liquid at room temperature; kink in the chain

    Types of Fatty Acids: Degree of Unsaturation

    • Saturated fatty acid: contains only single bonds
      • Linear form, High melting point, exist as solids
    • Unsaturated fatty acid: contains one or more double bonds
      • Kink in the chain, low melting point, exists as liquids
      • Mono, di, or polyunsaturated, depending on number of double bonds
    • Cis vs trans:
      • Cis: hydrogen atoms are on same side of the double bond
      • Trans: hydrogen atoms on opposite sides of the double bond

    Types of Fatty Acids: Length of Hydrocarbon Chain

    • Short-chain fatty acids (SCFAs) <6 carbons
    • Medium-chain fatty acids (MCFAs) 6-12 carbons
    • Long-chain fatty acids (LCFAs) >12 carbons
    • Very long-chain fatty acids (VLCFAs) >22 carbons

    How a Fatty Acid is Abbreviated

    • Saturated: number of carbons: 0 (e.g., 16:0)
    • Unsaturated: number of carbons: number of double bonds, placement of double bonds (e.g., 18:1(Δ9))

    Phospholipids

    • Lipids with amphiphilic molecules (both hydrophobic and hydrophilic parts)
    • Essential components of cell membranes, act as surface active agents (surfactants), and emulsifying agents
    • Phospholipid bilayer structure is essential for membrane structure

    Phospholipid Structure

    • Two fatty acid chains attached to glycerol
    • Phosphate group attached to glycerol
    • Hydrophilic head (frequently a choline group), and hydrophobic tails

    Types of Sphingolipids

    • Sphingophospholipids: phosphorus-containing molecules found mainly in nerve and brain cell membranes
    • Sphingoglycolipids : ceramide with one or more sugar residues
    • Ceramide: fatty acid joined to sphingosine via an amide bond

    Waxes

    • Esters of long-chain alcohols and long-chain fatty acids
    • Weakly polar head group attached to 2 hydrocarbon chains
    • Highly insoluble in water – water repellant
    • Functions: energy storage; structural components; increased rigidity with hydrocarbon chain length and saturation degree
    • Examples: beeswax, carnauba wax, spermaceti wax

    Terpenes

    • Contain repeating isoprene units
    • Mostly hydrocarbons but some contain oxygen
    • Found in essential oils – e.g. limonene, citronellal, menthol

    Steroids

    • Complex derivatives of triterpenes; squalene
    • Consist of membered rings (A, B, C, and D) fused together (e.g., cyclopentanoperhydrophenantrene)
    • Examples: cholesterol, sterols, hormones, bile acids

    Cholesterol

    • Sterol in animals; principal component of animal cell membranes
    • Weakly amphiphilic and rigid
    • Cholesteryl ester: ester of cholesterol between -COO of fatty acid and -OH of cholesterol
    • Functions of Cholesterol: precursor to steroid hormones, formation of bile acids

    Lipoproteins

    • Any lipids covalently linked to proteins
    • Found in blood plasma
    • Transport lipids, phospholipids, and cholesterol in the bloodstream
    • Classified according to density

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    Biomolecules II: Lipids PDF

    Description

    Test your knowledge of lipids, their structures, and functions. This quiz covers key aspects of lipid classification, identifying major lipid types such as fatty acids and phospholipids, and understanding their roles in biological systems. Dive in to see how well you understand these essential biomolecules!

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