Unsaturated Fatty Acids: Structure and Properties
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Questions and Answers

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

  • They are always spaced at two carbon intervals
  • They are always present at the end of the hydrocarbon tail
  • They are always in the trans configuration
  • They are nearly always in the cis configuration (correct)

    • What is the effect of introducing a cis double bond in a fatty acid?

  • It has no effect on the shape of the acid
  • It makes the acid straighter at that position
  • It increases the melting point of the fatty acid
  • It causes the acid to bend or 'kink' at that position (correct)

    • What is the relationship between the number of double bonds and the melting point of a fatty acid?

  • The more double bonds, the higher the melting point
  • The fewer double bonds, the lower the melting point
  • The more double bonds, the lower the melting point (correct)
  • There is no correlation between the two

    • What is the characteristic of the length of the hydrocarbon tail and the melting point of a fatty acid?

    <p>As the length increases, the melting point increases</p> Signup and view all the answers

    What is the role of α-Linolenic acid (plant omega-3) in the body?

    <p>It is a precursor of long-chain omega-3 polyunsaturated fatty acids</p> Signup and view all the answers

    What is the central architectural feature of biological membranes?

    <p>A double layer of lipids</p> Signup and view all the answers

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

    <p>To emulsify dietary fats</p> Signup and view all the answers

    What is the role of cholesterol in myelin sheath?

    <p>To provide insulation for efficient conduction of impulses</p> Signup and view all the answers

    What is the precursor molecule for the synthesis of vitamin D and steroid hormones?

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

    What is the primary source of acetyl-CoA for cholesterol synthesis?

    <p>β-oxidation of fatty acids</p> Signup and view all the answers

    What is the first step in the biosynthesis of cholesterol?

    <p>Biosynthesis of mevalonate</p> Signup and view all the answers

    What is the target of statins in cholesterol synthesis?

    <p>HMG-CoA reductase</p> Signup and view all the answers

    In which tissue are maximum amounts of glycolipids found?

    <p>Nervous tissue</p> Signup and view all the answers

    What is the role of gangliosides in the body?

    <p>Receptor for certain toxins and pathogens</p> Signup and view all the answers

    What is the origin of the five-carbon ring in prostaglandins?

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

    What is the effect of PGE and PGI on blood pressure?

    <p>Decrease peripheral resistance</p> Signup and view all the answers

    Which of the following is a function of prostaglandins?

    <p>Inflammatory mediator</p> Signup and view all the answers

    What is the origin of the name 'prostaglandin'?

    <p>Prostate gland</p> Signup and view all the answers

    What serves as an intracellular second messenger system in cells?

    <p>Inositol triphosphate and diacyl glycerol</p> Signup and view all the answers

    What is the primary function of sphingolipids in cells?

    <p>To anchor certain proteins to the cell</p> Signup and view all the answers

    What is the characteristic of sphingolipids that distinguishes them from other membrane lipids?

    <p>They contain no glycerol</p> Signup and view all the answers

    What is the characteristic of cerebrosides and globosides?

    <p>They have no charge at pH 7</p> Signup and view all the answers

    What is the characteristic of gangliosides?

    <p>They have oligosaccharides as their polar head groups</p> Signup and view all the answers

    What is the common component of sphingolipids?

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

    What is the product of the phosphorylation and decarboxylation of mevalonate?

    <p>Isopentenyl diphosphate</p> Signup and view all the answers

    What is the result of the condensation reaction between geranyl pyrophosphate and isopentenyl diphosphate?

    <p>Farnesyl diphosphate</p> Signup and view all the answers

    What is the enzyme responsible for converting squalene to 2,3-oxidosqualene?

    <p>Squalene epoxidase</p> Signup and view all the answers

    What is the immediate product of the cyclization of 2,3-oxidosqualene?

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

    Where does the formation of cholesterol from lanosterol take place?

    <p>Endoplasmic reticulum</p> Signup and view all the answers

    What is the result of the condensation of two molecules of farnesyl diphosphate?

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

    Study Notes

    Inositol Triphosphate and Diacylglycerol

    • Generated from phosphatidyl inositol biphosphate, serving as an intracellular second messenger system.
    • Plays a role in anchoring certain proteins to the cell membrane.

    Sphingolipids Overview

    • Fourth major class of membrane lipids, alongside phospholipids, glycolipids, and cholesterol.
    • Composed of sphingosine, long-chain fatty acid, and a polar head group without glycerol.

    Classification of Sphingolipids

    • Derivatives of ceramide with varying head groups.
    • Sphingomyelins: Contain phosphocholine or phosphoethanolamine.
    • Glycosphingolipids:
      • Cerebrosides: One monosaccharide linked to ceramide.
      • Globosides: Two or more monosaccharides linked.
      • Gangliosides: Complex lipids with oligosaccharides and sialic acid residues.

    Functions of Cholesterol

    • Polar derivatives form bile acids, acting as detergents to emulsify dietary fats.
    • Integral to the myelin sheath in neurons, aiding impulse conduction.
    • Precursor for vitamin D and steroid hormones (cortisol, aldosterone, progesterone, estrogens, testosterone).

    Cholesterol Synthesis Steps

    • Step 1: Biosynthesis of Mevalonate

      • Acetyl-CoA condenses to form acetoacetyl-CoA.
      • HMG-CoA synthesized; its reduction to mevalonate is the primary regulatory step, inhibited by statins.

    • Step 2: Formation of Squalene

      • Involves conversion of mevalonate to farnesyl pyrophosphate and then to squalene.

    Unsaturated Fatty Acids

    • Monounsaturated contains one double bond; polyunsaturated contains multiple.
    • Double bonds often in cis configuration, causing "kinks."
    • Melting point is influenced by the number and configuration of double bonds and fatty acid tail length.

    Essential Fatty Acids

    • Cannot be synthesized by the body; must be obtained from diet.
    • α-Linolenic acid (omega-3) is a precursor for long-chain PUFAs (EPA, DHA).
    • Linoleic acid is a precursor for omega-6 fatty acid arachidonic acid.

    Structural Lipids in Cell Membranes

    • Biological membranes feature a lipid bilayer, preventing polar molecules' passage.
    • Glycolipids are abundant in nervous tissue; galactocerebrosides found in myelin.

    Functions of Sphingolipids

    • Important for cell-cell interaction, growth, and development.
    • Antigenic properties linked to tumors and blood group antigens.
    • Gangliosides act as receptors for toxins and pathogens (e.g., cholera toxin).

    Eicosanoids

    • Prostaglandins: Contain a five-carbon ring derived from arachidonic acid.
      • Control blood pressure and act as inflammatory mediators by increasing capillary permeability.

    Synthesis of Prostaglandins

    • Involves sequential phosphorylation and decarboxylation of mevalonate to yield isopentenyl diphosphate and subsequently farnesyl pyrophosphate.

    Final Steps in Cholesterol Formation

    • Squalene undergoes cyclization to form lanosterol, then is converted into cholesterol in the endoplasmic reticulum.

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    Description

    Test your knowledge on the characteristics of unsaturated fatty acids, including their structure, double bonds, and melting point. Learn how the presence of double bonds affects the fatty acid molecule and its properties.

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