Lipids: Composition and Functions
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Questions and Answers

What is the general structure of fatty acids represented by?

  • R—CO—OH (correct)
  • R—CO—O
  • R—CO—NH2
  • R—C=O

    • Which of the following fatty acids has an even number of carbon atoms?

  • Butyric acid (correct)
  • Capric acid (correct)
  • Palmitoleic acid
  • Propionic acid

    • What differentiates saturated fatty acids from unsaturated fatty acids?

  • Hydroxyl group content
  • Length of hydrocarbon chain
  • Presence of a double bond (correct)
  • Number of carbon atoms

    • What type of fatty acid has a carbon chain length of 8 to 14 carbon atoms?

    <p>Medium chain fatty acids</p> Signup and view all the answers

    Which of the following is an example of an odd chain fatty acid?

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

    What is the primary component that makes lipids insoluble in water?

    <p>Hydrophobic nature</p> Signup and view all the answers

    Which fatty acids are defined by having two or more double bonds?

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

    What is the role of glycerol in lipids?

    <p>To serve as a backbone for fatty acids</p> Signup and view all the answers

    What term describes fatty acids that contain two or more double bonds?

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

    In the cis configuration of fatty acids, how are the radicals oriented around the double bond?

    <p>On the same side of the bond</p> Signup and view all the answers

    Which of the following fatty acids is an example of a trans fat?

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

    What does the notation '18:1; 9' indicate about oleic acid?

    <p>18 carbon atoms with 1 double bond at position 9</p> Signup and view all the answers

    What is the suffix used for saturated fatty acids in nomenclature?

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

    Which system numbers carbon atoms from the methyl end of the fatty acid molecule?

    <p>Omega (ω) nomenclature</p> Signup and view all the answers

    How many positional isomers can oleic acid have?

    <p>15</p> Signup and view all the answers

    What characteristic distinguishes trans fatty acids from their cis counterparts?

    <p>Trans fats have radicals on opposite sides of the double bond</p> Signup and view all the answers

    What type of fatty acids predominantly found in coconut oil are classified as medium chain TAG?

    <p>Lauric and Myristic acids</p> Signup and view all the answers

    Which of the following components are found in phospholipids?

    <p>Fatty acids, an alcohol, and phosphoric acid residue</p> Signup and view all the answers

    Which of these lipids is classified as a derived lipid?

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

    What is the primary function of triglycerides in the body?

    <p>Store energy</p> Signup and view all the answers

    Which of the following describes the structure of cholesterol?

    <p>Amphipathic with a polar head and hydrophobic tail</p> Signup and view all the answers

    Which of the following is NOT a function of lipids?

    <p>Act as enzymes</p> Signup and view all the answers

    Which type of lipids are characterized by containing both sugars and fatty acids?

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

    What characteristic do neutral lipids such as cholesterol and cholesteryl esters possess?

    <p>They have nonpolar characteristics</p> Signup and view all the answers

    What type of fatty acid is linoleic acid classified as?

    <p>Omega-6 fatty acid</p> Signup and view all the answers

    How do the melting points of fatty acids change with respect to chain length and unsaturation?

    <p>Increase with chain length and decrease with unsaturation</p> Signup and view all the answers

    What are essential fatty acids?

    <p>Fatty acids that must be consumed in the diet</p> Signup and view all the answers

    Which of the following best describes fats at room temperature?

    <p>They are solid and primarily saturated</p> Signup and view all the answers

    What is the primary characteristic that differentiates oils from fats?

    <p>Oils are liquids at room temperature</p> Signup and view all the answers

    What type of lipids contains esters of fatty acids with higher molecular weight monohydric alcohols?

    <p>Simple lipids</p> Signup and view all the answers

    What happens to lipids in regions of the body subjected to cooling, such as extremities?

    <p>They contain more unsaturated fatty acids</p> Signup and view all the answers

    What is primarily true about triacylglycerols that contain short-chain triglycerides?

    <p>They are insoluble in water</p> Signup and view all the answers

    What is the primary function of triacylglycerols in the body?

    <p>Store energy as fat</p> Signup and view all the answers

    Which type of lipid is primarily responsible for lowering surface tension in the alveoli of the lungs?

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

    Which phospholipid is the most abundant in cell membranes and plays a key role in nervous transmission?

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

    What distinguishes sphingomyelins from other phospholipids?

    <p>They yield sphingosine upon hydrolysis</p> Signup and view all the answers

    Which of the following lipids is involved in apoptosis?

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

    Why do triacylglycerols require minimal space compared to hydrated glycogen?

    <p>They are non-polar and repel water</p> Signup and view all the answers

    What characteristic do phospholipids share that makes them suitable for forming cell membranes?

    <p>They have both hydrophobic and hydrophilic regions</p> Signup and view all the answers

    In which layer of the cell membrane are sphingomyelins primarily found?

    <p>Outer layer</p> Signup and view all the answers

    What effect does lower temperature have on the fluidity of the cell membrane?

    <p>Decreases membrane fluidity</p> Signup and view all the answers

    How do lipid soluble substances travel across the cell membrane?

    <p>Via simple diffusion</p> Signup and view all the answers

    What is the significance of the asymmetry in membrane phospholipids?

    <p>It aids in cell signaling and maintaining membrane shape</p> Signup and view all the answers

    Which type of proteins are primarily responsible for the movement of ions and small molecules across the membrane?

    <p>Integral protein channels</p> Signup and view all the answers

    What role do sphingomyelins play in cell membranes?

    <p>They are involved in cell signaling and apoptosis</p> Signup and view all the answers

    What happens to phospholipids at high temperatures?

    <p>They have higher kinetic energy, increasing membrane fluidity</p> Signup and view all the answers

    What can excessive fat deposits lead to in terms of health?

    <p>Obesity and increased risk of heart attack</p> Signup and view all the answers

    Which of the following best describes the role of integral proteins in the cell membrane?

    <p>They facilitate the movement of non-lipid soluble substances</p> Signup and view all the answers

    Study Notes

    Lipids: Composition, Structure, and Functions

    • Lipids are a heterogeneous group of organic substances found in plant and animal tissues.
    • They are relatively insoluble in water but soluble in nonpolar organic solvents (e.g., benzene, chloroform, ether).
    • Lipids consist of carbon, hydrogen, and oxygen.
    • Lipids are made up of fatty acids and glycerol.

    Lesson Learning Outcomes

    • Students should be able to describe the general structure of lipids.
    • Students should be able to classify lipids and fatty acids.
    • Students should be able to describe the physiochemical properties of lipids.
    • Students should be able to describe the functions of lipids.
    • Students should be able to outline the clinical significance of lipids.

    Glycerol

    • Glycerol is an alcohol with three carbons, five hydrogens, and three hydroxyl (OH) groups.

    Fatty Acids

    • Fatty acids are aliphatic carboxylic acids.
    • The general formula is R-CO-OH.
    • The COOH group represents the functional group.
    • Physical properties vary depending on the R group (hydrocarbon chain).

    Classification of Fatty Acids

    • Based on the number of carbon atoms:
      • Even-chain fatty acids are prevalent in naturally occurring lipids (e.g., 2, 4, 6, etc.).
      • Odd-chain fatty acids are found in microbial cell walls and milk (e.g., 3, 5, 7, etc.).
    • Based on the length of the hydrocarbon chain:
      • Short-chain (2-6 carbon atoms).
      • Medium-chain (8-14 carbon atoms).
      • Long-chain (16 or more, often up to 24 carbon atoms).
      • Very long-chain (more than 24 carbon atoms).
    • Based on the nature of the hydrocarbon chain:
      • Saturated fatty acids: contain only single bonds.
      • Unsaturated fatty acids:
        • Monoenoic (monounsaturated): one double bond.
        • Polyenoic (polyunsaturated): two or more double bonds.
      • Branched-chain fatty acids.
      • Hydroxy fatty acids.

    Isomerism

    • Geometric Isomers:
      • Cis isomers have substituents on the same side of the double bond (often more reactive).
      • Trans isomers have substituents on opposite sides of the double bond.
    • Positional Isomers: Variations in the location of double bonds create different isomers.

    Nomenclature of Fatty Acids

    • Fatty acids are often expressed using a formula system indicating the number of carbon atoms, double bonds, and positions of the double bonds (e.g., 18:1;9).
    • Another naming system uses the Greek letter omega (ω) to indicate the position of the last double bond starting from the methyl end of the fatty acid molecule.

    Saturated Fatty Acids

    • General formula: CH3-(CH2)n-COOH
    • Examples include acetic acid, butyric acid, palmitic acid, and stearic acid.

    Unsaturated Fatty Acids

    • The presence of at least one double bond makes a fatty acid unsaturated.
    • Polyunsaturated fatty acids have two or more double bonds.
    • Unsaturated fatty acids exhibit geometrical isomerism at the double bonds.

    Essential Fatty Acids

    • Essential fatty acids cannot be synthesized in the body and must be obtained from the diet.
    • Lack of essential fatty acids can cause growth retardation and other deficiency symptoms.
    • Examples include linoleic acid (ω-6) and linolenic acid (ω-3).
    • Arachidonic acid (ω-6) is not essential but important for various functions.

    Physical and Physiologic Properties of Fatty Acids

    • Melting points increase with chain length and decrease with unsaturation.
    • A triacylglycerol with 12+ carbons or more saturated fatty acids at body temperature is solid.
    • A triacylglycerol containing polyunsaturated fatty acids is liquid below 0°C.

    Classification of Lipids

    • Simple lipids: Esters of fatty acids with glycerol or other higher alcohols.
      • Fats (solid)
      • Oils (liquid)
      • Waxes (esters of fatty acids with higher molecular weight alcohols)
    • Compound lipids: Fatty acids esterified with an alcohol and other groups.
      • Phospholipids (contain phosphoric acid)
        • Glycerophospholipids (glycerol as alcohol).
        • Sphingophospholipids (sphingosine as alcohol).
      • Glycolipids (contain a carbohydrate).
      • Other complex lipids (e.g., sulfolipids, amino lipids, lipoproteins).
    • Derived lipids: Products of the hydrolysis of simple and compound lipids.
      • Fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, ketone bodies, hydrocarbons, lipid-soluble vitamins and micronutrients.
      • Neutral lipids (uncharged acylglycerols, cholesterol, and cholesteryl esters).
      • Sterols (e.g., cholesterol).

    Functions of Lipids

    • Storage form of energy (triglycerides).
    • Structural components of biomembranes (phospholipids and cholesterol).
    • Metabolic regulators (steroid hormones and prostaglandins).
    • Insulation against temperature changes (fat).
    • Protection of internal organs.
    • Aid in absorption of fat-soluble vitamins (A, D, E, K).
    • Improve taste and palatability of food.
    • Act as surfactants, detergents, and emulsifying agents.

    Clinical Applications

    • Excessive fat deposits cause obesity.
    • Abnormalities in cholesterol and lipoprotein metabolism lead to atherosclerosis and cardiovascular diseases.
    • Diabetes mellitus can lead to ketosis, affecting fatty acid and lipoprotein metabolisms.

    Saponification

    • Hydrolysis of triacylglycerols by alkali produces glycerol and soaps.

    Lipid Peroxidation

    • Peroxidation of lipids exposed to oxygen can cause food spoilage (rancidity), and damage to living tissues.
    • It is a chain reaction involving reactive oxygen species.
    • Antioxidants can control and reduce lipid peroxidation.

    Membrane Functions

    • Fluidity: influenced by cholesterol, chain length, and saturation of fatty acid tails.
    • Permeability: cell membranes have selective permeability barrier function.
    • Shape: cell membrane asymmetry of phospholipids (e.g., outer leaflet: choline-containing phospholipids; inner leaflet: amino phospholipids).

    Phospholipids

    • The main lipid components of membranes.
    • Amphipathic, with both hydrophobic and hydrophilic portions.
    • Examples include phosphatidylcholines (lecithins), sphingomyelins, phosphatidylethanolamine (cephalin), phosphatidylserine, and phosphatidylinositol.

    Cardiolipin

    • Found only in mitochondria.
    • Essential for mitochondrial function.
    • Decreased levels or alterations affect mitochondrial function and can contribute to various diseases.

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    Explore the fascinating world of lipids, including their structure, classification, and functions in biological systems. This quiz will cover the key properties of lipids and their clinical significance, helping students deepen their understanding of this essential topic in biochemistry.

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