Lipids Overview
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What is the primary reason that certain fatty acids are classified as essential for humans?

  • Humans lack the enzymes to insert double bonds at certain carbon atoms. (correct)
  • Humans can easily synthesize all fatty acids.
  • All fatty acids are readily available in the diet.
  • Essential fatty acids are not required for membrane structure.

    • Which fatty acid is designated as 18:3 n-3?

  • Eicosapentaenoic acid
  • Linoleic acid
  • Alpha-linolenic acid (correct)
  • Docosahexaenoic acid

    • Which of the following is NOT a good source of omega-6 fatty acids?

  • Corn oil
  • Oily fish (correct)
  • Poultry
  • Cotton seed oil

    • What type of compound are triacylglycerols considered to be?

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

    How many fatty acid molecules are esterified with one glycerol molecule in fats?

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

    What is the correct structure for the shorthand representation of linoleic acid?

    <p>18:2 n-6</p> Signup and view all the answers

    Which of the following roles do essential fatty acids play in the body?

    <p>Formation of lipoproteins</p> Signup and view all the answers

    What is the common name for the fatty acid referred to as EPA?

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

    What is the main characteristic of saturated fatty acids?

    <p>All carbon atoms are bonded to hydrogen with no double bonds.</p> Signup and view all the answers

    Which fatty acids are known to be liquid at room temperature?

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

    What is the reason most naturally occurring unsaturated fatty acids are cis-isomers?

    <p>Cis isomers fit better into cell membranes.</p> Signup and view all the answers

    What percentage of fatty acids found in plasma are in the form of fatty acid esters?

    <p>More than 90%</p> Signup and view all the answers

    What impact does the double bond in unsaturated fatty acids have on their structure?

    <p>It introduces a kink in the chain.</p> Signup and view all the answers

    Which fatty acids are primarily associated with animal fats and typically solid at room temperature?

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

    What is a key consequence of consuming saturated fatty acids?

    <p>Increased likelihood of atherosclerosis.</p> Signup and view all the answers

    What structural feature leads to the high water-insolubility of long-chain fatty acids?

    <p>A predominantly hydrophobic region.</p> Signup and view all the answers

    Which of the following correctly describes the solubility characteristics of lipids?

    <p>Lipids are insoluble in water and soluble in nonpolar solvents.</p> Signup and view all the answers

    Which function of lipids primarily serves to protect against cold?

    <p>Thermal insulation</p> Signup and view all the answers

    What is the significance of lipids as sources of energy compared to carbohydrates and proteins?

    <p>Lipids have a higher energy content than carbohydrates.</p> Signup and view all the answers

    Which lipid serves as a precursor in the synthesis of cholesterol?

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

    What role do lipoproteins play in the human body?

    <p>Transport complexes for lipids in the blood.</p> Signup and view all the answers

    Which statement correctly identifies an antimicrobial function of certain lipids?

    <p>Some saturated fatty acids act as antimicrobial agents.</p> Signup and view all the answers

    How do eicosanoids derived from essential fatty acids impact the body?

    <p>They have profound biological actions.</p> Signup and view all the answers

    In what way are lipids involved as antigens in certain diseases?

    <p>Anti-lipid antibodies are found in individuals affected by specific parasitic diseases.</p> Signup and view all the answers

    What is the main role of structural lipoproteins in lung tissues?

    <p>Acting as surfactants</p> Signup and view all the answers

    Which of the following lipoproteins is primarily responsible for transporting exogenous lipids from the intestine?

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

    How do the density and size of plasma lipoproteins relate to their lipid content?

    <p>Higher lipid content leads to lower density</p> Signup and view all the answers

    Which of the following is not a characteristic of LDL?

    <p>Transport triglycerides to cells</p> Signup and view all the answers

    What percentage of Chylomicrons is composed of protein?

    <p>1%</p> Signup and view all the answers

    Which lipoprotein is typically undetectable in normal plasma?

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

    What major component makes up VLDL in terms of percentage?

    <p>50 - 55% triglyceride</p> Signup and view all the answers

    Which lipoprotein is involved in transporting cholesterol from cells to the liver?

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

    What are gangliosides primarily composed of?

    <p>Ceramide and oligosaccharides with sialic acids</p> Signup and view all the answers

    What role do gangliosides play in neurons?

    <p>They attract positive ions and affect electrical properties.</p> Signup and view all the answers

    Which of the following best describes GM1 ganglioside?

    <p>A site for cholera toxin attachment</p> Signup and view all the answers

    How do gangliosides contribute to blood group determination?

    <p>They determine the type of blood through carbohydrate moieties.</p> Signup and view all the answers

    What is one potential therapeutic use of natural and semi-synthetic gangliosides?

    <p>Treating neurodegenerative disorders</p> Signup and view all the answers

    Which of the following statements about glycolipids is true?

    <p>They function as receptors for specific viruses.</p> Signup and view all the answers

    What is a characteristic feature of lipid rafts?

    <p>They involve higher concentrations of sphingolipids and cholesterol.</p> Signup and view all the answers

    What types of components do lipoproteins contain?

    <p>Combination of lipids like phospholipids, cholesterol, and proteins</p> Signup and view all the answers

    What is the primary role of high density lipoproteins (HDL) in the body?

    <p>Transport cholesterol from tissues back to the liver</p> Signup and view all the answers

    Which of the following is NOT a component of low density lipoproteins (LDL)?

    <p>Apolipoprotein A-I</p> Signup and view all the answers

    How is LDL cholesterol generally characterized?

    <p>Bad cholesterol that can lead to artery buildup</p> Signup and view all the answers

    What percentage of protein is found in high density lipoproteins (HDL)?

    <p>33 - 57 %</p> Signup and view all the answers

    What is the impact of high levels of HDL on heart attack risk?

    <p>Decreases heart attack risk</p> Signup and view all the answers

    Which apolipoprotein is primarily associated with high density lipoproteins (HDL)?

    <p>Apo-AI</p> Signup and view all the answers

    Which statement about cholesterol's solubility is true?

    <p>Cholesterol is hydrophobic and cannot mix with blood</p> Signup and view all the answers

    What is the density characteristic of lipoproteins related to their lipid content?

    <p>Higher lipid content results in lower density</p> Signup and view all the answers

    Study Notes

    Lipids

    • Lipids are a heterogeneous group of organic compounds
    • Defined by solubility in nonpolar solvents (chloroform, ether, benzene) and poor solubility in water
    • Unlike other polymers (polysaccharides, proteins, nucleic acids), lipids are not polymers
    • Mostly small molecules
    • Can be polar or nonpolar (amphipathic)
    • Major polar lipids include fatty acids, cholesterol, glycerophosphatides, and glycosphingolipids
    • Very short chain fatty acids and ketone bodies are readily soluble in water
    • Present in humans, animals, plants, and microorganisms to some extent
      • Animal fat, egg yolk, butter, and cheese are animal-origin lipids
      • Vegetable/cooking oils are plant-origin lipids

    Functions of Lipids

    • Thermal insulator against cold (under skin)
    • Padding against injury (fat around kidneys)
    • Energy source for cells, comparable to carbohydrates
    • Ideal for energy storage in humans because of higher energy content compared to carbohydrates and proteins
    • Structural components of cell membranes and nervous tissue
    • Precursors for complex molecules (e.g., acetyl-CoA for cholesterol synthesis)
    • Involved in lipid transport in blood as lipoproteins
    • Hormones and fat-soluble vitamins are lipids
    • Essential for fat-soluble vitamin absorption

    Classification of Lipids

    • Simple lipids: Esters of fatty acids with different alcohols
      • Fats and oils (TAGs): Esters of fatty acids with glycerol
      • Physical difference: Oil is liquid at room temperature; fat is solid.
    • Complex (compound) lipids: Esters of fatty acids with alcohols containing additional groups (phosphate, nitrogenous base, carbohydrate, protein, etc.)
      • Phospholipids:
      • Glycerophospholipids (e.g., lecithin, cephalin): Contains glycerol
      • Sphingophospholipids (e.g., sphingomyelin): Contains sphingosine
      • Glycolipids: Contain fatty acid, carbohydrate, and nitrogenous base.
      • Examples: Cerebrosides, gangliosides.
      • The alcohol is typically sphingosine, hence glycosphingolipids.
      • Glycerol and phosphate are missing.
      • Lipoproteins: Macromolecular complexes of lipids with proteins involved in transporting lipids in blood.
      • Other complex lipids: Sulfolipids, amino lipids, and lipopolysaccharides
    • Derived lipids: Derivatives obtained after hydrolysis of simple and complex lipids
      • Examples: Fatty acids, monoglycerides, diglycerides, steroid hormones, fat-soluble vitamins, ketone bodies.
    • Miscellaneous lipids: Large number of compounds with lipid properties
      • Examples: Carotenoids, squalene, hydrocarbons (e.g., pentacosane in beeswax), terpenes.

    Fatty Acids

    • Carboxylic acids with hydrocarbon side chains
    • Simplest form of lipids
    • Anionic group has an affinity for water, giving amphipathic nature (hydrophilic and hydrophobic regions)
    • Fatty acids with less than 12 and more than 24 carbon atoms are uncommon
    • Palmitic acid (16C) and stearic acid (18C) are the most common
    • Most have an even number of carbon atoms due to biosynthesis of fatty acids with sequential addition of 2 carbon units
    • Long-chain fatty acids (LCFAs) are hydrophobic and need protein for transport in circulation. LCFA comprise more than 90% of plasma fatty acids in ester forms

    Saturated vs. Unsaturated Fatty Acids

    • Saturated: No double bonds, long straight chains, solid at room temperature, contribute to cardiovascular disease (atherosclerosis).
    • Unsaturated: Contain one or more double bonds, create kinks, liquid at room temperature, are more prominent in plant and fish fats and vegetable oils.

    Trans Fats

    • Formed when hydrogen is added to unsaturated fats (hydrogenation)
    • More solid than oils
    • Increase shelf life of foods

    Fatty Acid Structure

    • Double bonds create kinks, prevent close packing, thus less Van der Waals interactions making the substance more fluid and decreasing melting points in room temperature.

    The Peanut Butter Puzzle

    • Fats are typically found in animals, and Oils in plants.
    • Peanut butter is solid due to hydrogenation.

    Essential Fatty Acids

    • Not synthesized in the body
    • linoleic acid (precursor to arachidonic acid, used in prostaglandin synthesis) crucial for growth and development
    • a-linolenic acid important for growth and development
    • Arachidonic acid becomes essential if linoleic acid is deficient in the diet

    Storage Lipids

    • Fats and oils are used for energy storage
    • Two main types: Triacylglycerols and Waxes
    • Triacylglycerols are esters of fatty acids and glycerol in living organisms
    • Waxes are esters of long-chain fatty acids and long-chain alcohols

    Fats (Triacylglycerols)

    • Esters of fatty acids with glycerol
    • Also called triglycerides or triacylglycerols
    • All three hydroxyl groups of glycerol are esterified
    • Commonly called neutral fats

    Steroids

    • Complex molecules containing four fused rings
    • Include cyclopentanoperhydrophenanthrene (CPPP) or sterane ring

    Compound Lipids

    • Lipids that contain additional elements (i.e. additional to fatty acids and alcohols) in addition to fatty acids and alcohols.
    • Examples: Phospholipids, Glycolipids, and lipoproteins

    Cardiolipin

    • Component of the inner mitochondrial membrane
    • Only human glycerophospholipid that is antigenic
    • Used in serological diagnosis of syphilis and autoimmune diseases.

    Plasmalogens

    • Ether linkage. Acyl group
    • Glycerol backbone.

    Platelet-Activating Factor (PAF)

    • Synthesized by variety of cell types
    • Binds to surface receptors, triggering thrombotic and inflammatory events
    • Activates inflammatory cells, mediating hypersensitivity, acute inflammatory, and anaphylactic reactions
    • Causes platelets to aggregate.

    Sphingophospholipids (Sphingomyelin)

    • Important component of nerve tissue (myelin sheath)
    • Insulate and protect central nervous system fibers.

    Glycolipids

    • Contains carbohydrate residues, and a very long chain fatty acid (sphingosine),
    • Found in cerebral tissues
    • Classified based on carbohydrate presence (e.g., cerebrosides, gangliosides, sulfatides)

    Gangliosides

    • Compound lipids in the gray matter of the brain, ganglionic cells, and RBCs
    • Composed of ceramide and oligosaccharides with one or more sialic acids linked to a sugar chain
    • Classified based on their oligosaccharide attached to the ceramide.

    Membrane Lipids

    • Located in cellular and subcellular membranes.
      • e.g. Glycerophospholipids, Sphingolipids, and Glycolipids

    Lipid Rafts

    • Have higher concentrations of sphingolipids, cholesterol, and glycolipids.

    Lipoproteins

    • Lipids combined with proteins
    • Two types: Structural and Transport
    • Structural: Widely distributed in tissues (e.g., lungs and eye).

    Lipoprotein Classification

    • Classified based on density, which reflects size and lipid/protein ratio.
      • Chylomicrons, largest and least dense, transport dietary triglycerides.
      • Very low-density lipoproteins (VLDL): Transport endogenous triglycerides form the liver to cells
      • Intermediate-density lipoproteins (IDL): Formed during VLDL conversion into LDL, usually undetectable in normal plasma.
      • Low-density lipoproteins (LDL): Carry cholesterol from VLDL or IDL to cells.
      • High-density lipoproteins (HDL): Transport cholesterol from cells back to the liver.

    LDL and HDL

    • LDL cholesterol is 'bad' because high levels contribute to buildup of cholesterol in arteries, thus increasing the risk of heart disease.
    • HDL cholesterol is 'good' because it transports cholesterol from cells back to the liver for removal.

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    Description

    This quiz covers the essential aspects of lipids, including their classification, structure, and functions in biological systems. Learn about their properties, types, and roles as energy sources and structural components in living organisms.

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