Lecture 22
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Questions and Answers

What is the direction of numbering carbons in the alternative convention for polyunsaturated fatty acids?

  • From the omega carbon to the alpha carbon
  • From the methyl group to the carboxyl group (correct)
  • From the alpha carbon to the omega carbon
  • From the carboxyl group to the methyl group

    • Which of the following omega-3 fatty acids can be synthesized from ALA?

  • Only DHA
  • Both DHA and EPA (correct)
  • Only EPA
  • Neither DHA nor EPA

    • What is the notation for Palmitoleic acid, a C16 mono-unsaturated fatty acid?

  • 16:1(D8)
  • 16:1(D9) (correct)
  • 16:2(D9,12)
  • 16:0

    • What is the name of the omega-3 fatty acid found in soybeans and flaxseeds?

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

    What is the function of the ω notation in the alternative convention for polyunsaturated fatty acids?

    <p>Designates the methyl carbon at the end of the chain</p> Signup and view all the answers

    What is the primary function of bile acids in the intestine?

    <p>To emulsify dietary fats and make them more accessible to lipases</p> Signup and view all the answers

    What is the main difference between sterols and steroid hormones?

    <p>Sterols have an alkyl side-chain, while steroid hormones lack it</p> Signup and view all the answers

    What is the role of cholesterol in the plasma membrane?

    <p>To thicken the plasma membrane</p> Signup and view all the answers

    What is the source of cholesterol in mammals?

    <p>Both from food and de novo synthesis in the liver</p> Signup and view all the answers

    What is the primary role of steroid hormones in the body?

    <p>To carry messages between tissues</p> Signup and view all the answers

    What is the primary function of lipids in storing energy?

    <p>To store reduced compounds with high available energy</p> Signup and view all the answers

    What is the characteristic of the double bonds in natural unsaturated fatty acids?

    <p>They are commonly in cis configuration</p> Signup and view all the answers

    What is the role of vitamin K in biological functions of lipids?

    <p>It is involved in blood clot formation</p> Signup and view all the answers

    What is the characteristic of the hydrocarbon chain in fatty acids?

    <p>It is commonly unbranched with an even number of carbon atoms</p> Signup and view all the answers

    What is the significance of the hydrophobic nature of lipids in biological functions?

    <p>It provides insulation and prevents excessive wetting</p> Signup and view all the answers

    What is the common range of carbon atoms in natural fatty acids?

    <p>C4 to C36</p> Signup and view all the answers

    What is the primary function of eicosanoids in the body?

    <p>To act as paracrine hormones, mediating inflammation and vasoconstriction</p> Signup and view all the answers

    Which of the following hormones is NOT synthesized in the adrenal gland?

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

    What is the enzyme inhibited by nonsteroidal anti-inflammatory drugs (NSAIDs)?

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

    What is the role of prostaglandins and thromboxanes in the body?

    <p>To mediate inflammation, vasoconstriction, and platelet aggregation</p> Signup and view all the answers

    What is the primary source of estradiol in the body?

    <p>Ovaries and placenta</p> Signup and view all the answers

    What is the function of prednisone and prednisolone?

    <p>To act as anti-inflammatory agents</p> Signup and view all the answers

    What is the result of the photochemical reactions in the rhodopsin molecule when it is excited by visible light?

    <p>Conversion of 11-cis-retinal to all-trans-retinal</p> Signup and view all the answers

    What is the primary function of Vitamin E in the body?

    <p>Removal of free radicals</p> Signup and view all the answers

    What is the role of Vitamin K1 in the body?

    <p>Activation of blood-clotting factors</p> Signup and view all the answers

    What is the result of the transformation of the rhodopsin molecule in the rod cell of the vertebrate retina?

    <p>Sending of an electrical signal to the brain</p> Signup and view all the answers

    What is the result of the conversion of 11-cis-retinal to all-trans-retinal in the rhodopsin molecule?

    <p>A change in the shape of the rhodopsin molecule</p> Signup and view all the answers

    What is the primary function of vitamin E in the body?

    <p>To remove free radicals</p> Signup and view all the answers

    What is the role of isoprenoids in the body?

    <p>To form units of coenzyme Q</p> Signup and view all the answers

    What is the result of myristoylation, palmitoylation, and prenylation?

    <p>The addition of lipid groups to proteins</p> Signup and view all the answers

    What is the function of ubiquinone in the body?

    <p>To act as a coenzyme in energy metabolism</p> Signup and view all the answers

    What is the role of vitamin K in the body?

    <p>To activate blood-clotting factors</p> Signup and view all the answers

    What is the result of the transformation of the rhodopsin molecule in the rod cell of the vertebrate retina?

    <p>An electrical signal is sent to the brain</p> Signup and view all the answers

    What is the function of antioxidants in the body?

    <p>To remove free radicals</p> Signup and view all the answers

    What is the common characteristic of lipid quinones?

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

    Study Notes

    Biological Functions of Lipids

    • Lipids provide energy storage: reduced compounds with high energy density and hydrophobic nature for good packing
    • Insulation from the environment: low thermal conductivity, high heat capacity, and mechanical protection
    • Water repellence: hydrophobic nature keeps the surface of the organism dry, preventing excessive wetting and water loss

    Structure and Properties of Lipids

    • Fatty acids: carboxylic acids with hydrocarbon chains (C4-C36), even number of carbon atoms, unbranched, and saturated or unsaturated
    • Double bonds: cis configuration, kinking the chain
    • Two conventions for naming fatty acids: standard and alternative
    • Omega-3 fatty acids: essential nutrients, cannot be synthesized by humans, including ALA, DHA, and EPA

    Sterols

    • Sterol nucleus: 4 fused rings, almost planar, and relatively rigid
    • Amphipathic: polar (OH at C-3) and non-polar (hydrocarbon side-chain at C-17)
    • Synthesized from acetyl CoA via 5-carbon isoprene units
    • Cholesterol: major sterol in animals, structural lipid, and component of membranes

    Physiological Role of Sterols

    • Modulate fluidity and permeability
    • Thicken the plasma membrane
    • Present in the membranes of most eukaryotic cells
    • Mammals obtain cholesterol from food or synthesize it de novo in the liver

    Bile Acids

    • Produced in the liver and stored in the gallbladder
    • Act as detergents in the intestine, emulsifying dietary fats
    • Derivatives of cholesterol

    Steroid Hormones

    • Oxidized derivatives of sterols
    • Lack the alkyl chain found in cholesterol
    • More polar than cholesterol
    • Synthesized from cholesterol in gonads and adrenal glands
    • Carried through the body in the bloodstream, usually attached to carrier proteins

    Lipid-Soluble Vitamins

    • Vitamin D: regulates calcium uptake, plays a role in immunity, and can be synthesized in the skin
    • Vitamin A: plays a role in visual transduction and gene expression
    • Vitamin E: antioxidant, removes free radicals, and protects against nonenzymatic oxidation of macromolecules
    • Vitamin K: involved in carboxyglutamate formation and the activation of blood-clotting factors

    Eicosanoids

    • Derivatives of arachidonic acid
    • Paracrine hormones, carrying messages between nearby cells
    • Mediate inflammation, vasoconstriction, and platelet aggregation

    Lipid-Modified Proteins

    • Addition of lipid groups by myristoylation, palmitoylation, prenylation, farnesylation, etc.
    • Modulate protein function and localization

    Other Lipids

    • Lipid quinones: antioxidants, such as ubiquinone and dolichols
    • Isoprenoid derivatives: units derived from isoprene, found in various lipids

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