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 (B)</p> Signup and view all the answers

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

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

Phosphatidylcholine can also be referred to as what?

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

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

<p>Phospholipids (D)</p> Signup and view all the answers

Which statement about X-groups in phospholipids is true?

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

What type of sphingolipid is specifically associated with galactose?

<p>Galactocerebroside (C)</p> Signup and view all the answers

Which of the following best describes the character of waxes?

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

Which component is NOT typically found in terpenes?

<p>Nitrogen (A)</p> Signup and view all the answers

What structural feature do complex derivatives of triterpenes possess?

<p>Fused six-membered rings (B)</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 (B)</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. (A)</p> Signup and view all the answers

What is the main function of triacylglycerols in animals?

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

What type of reaction forms the ester bond in triacylglycerols?

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

What are adipocytes primarily responsible for?

<p>Synthesis and storage of triacylglycerols. (C)</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. (A)</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. (C)</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. (B)</p> Signup and view all the answers

What is the major structural component of lipids?

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

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

<p>Eicosanoids (D)</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 (D)</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) (B)</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 (C)</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 (D)</p> Signup and view all the answers

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

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

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

<p>Triacylglycerols (B)</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) (A)</p> Signup and view all the answers

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

<p>Sphingolipids (C)</p> Signup and view all the answers

What is one function of cholesterol in the body?

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

Which type of lipoprotein has the highest percentage of protein?

<p>HDL (B)</p> Signup and view all the answers

What is the primary function of bile acids?

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

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

<p>Polyunsaturates (A)</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 (C)</p> Signup and view all the answers

What is cholesteryl ester?

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

What is the density classification range for VLDL?

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

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

<p>Cholesterol (B)</p> Signup and view all the answers

Flashcards

Sphingolipids

A class of lipids containing sphingosine, long chain fatty acids, and a polar head group

Sphingoglycolipids

Sphingolipids with a carbohydrate head group.

Waxes

Esters of long-chain alcohols and long-chain fatty acids; highly insoluble in water.

Terpenes

Complex compounds composed of repeating isoprene units.

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Steroids

Complex derivatives of triterpenes, containing fused rings.

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Fatty acid abbreviation

A fatty acid is abbreviated using a number followed by a colon and another number. The first number indicates the total number of carbons in the chain, and the second number indicates the number of double bonds.

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ω-3 fatty acid

A fatty acid with the first double bond located on the third carbon atom from the methyl end (ω) of the carbon chain.

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Triacylglycerol

A molecule formed by attaching three fatty acids to a glycerol molecule via ester bonds.

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Triacylglycerol function

Triacylglycerols store energy, insulate against low temperatures, and make fur/feathers water-repellant.

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Adipose tissue

Tissue that contains cells (adipocytes) specialized in storing and synthesizing triacylglycerols.

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Fatty acid configuration

Double bonds in fatty acids are typically cis and separated by a methylene group unless specified.

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Ester bond formation

Ester bonds are formed by condensation reactions when fatty acids are attached to a glycerol molecule to create triacylglycerols.

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Adipocytes

Specialized cells that store triacylglycerols in adipose tissue.

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Lipid

A biomolecule that is generally insoluble in water but soluble in non-polar solvents. They have various structures and functions.

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Fatty Acid

A carboxylic acid with a long hydrocarbon side chain. Differentiated by chain length and presence of double bonds.

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Saturated Fatty Acid

Fatty acid with only single bonds.

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Unsaturated Fatty Acid

Fatty acid with one or more double bonds.

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Phospholipid

A lipid containing a phosphate group, contributing to its dual nature (hydrophilic head, hydrophobic tail), crucial for cell membranes.

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Short Chain Fatty Acid (SCFA)

Fatty acids with a hydrocarbon chain of under 6 carbons.

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Medium Chain Fatty Acid (MCFA)

Fatty acids with a hydrocarbon chain of 6-12 carbons.

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Lipid Functions

Lipids serve many roles, including energy storage, structural components (membranes), signaling molecules (hormones and eicosanoids), and more.

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Position of Double Bond (Fatty Acid)

The position of the double bond in a fatty-acid chain directly affects the physical characteristics of the fatty acid, affecting how they behave in various environments.

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Phospholipid Composition

Phospholipids consist of two fatty acids attached to glycerol, a glycerol molecule, a phosphate group attached to the glycerol, and a variable X group attached to the phosphate group.

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Phospholipid X group

The X group in a phospholipid is a variable group, changing the properties of the phospholipid. Examples include choline, ethanolamine, serine, and inositol.

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Sphingolipid structure

Sphingolipids are a type of lipid containing a sphingosine backbone, a fatty acid chain attached via an amide bond, and a variable group. They are important components of cell membranes.

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Sphingolipid types

Sphingolipids can be sub-categorized based on the nature of the variable group. One example is sphingophospholipids including sphingomyelin.

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Sphingomyelin

A specific type of sphingophospholipid important in cell membranes, especially in brain and nerve cells.

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Ceramide structure

Ceramide is a component of sphingolipids. It is formed by a fatty acid attached to sphingosine via an amide bond.

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Amphiphilic molecule

A molecule having both hydrophilic and hydrophobic portions, like phospholipids, essential for membrane formation.

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Cholesterol

A type of steroid, a major component of animal cell membranes, and precursor to steroid hormones.

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Cholesteryl Ester

A chemical compound formed from a cholesterol molecule linked to a fatty acid.

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Lipoproteins

Proteins that carry lipids (fats) around the bloodstream to different parts of the body.

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Function of Cholesterol

Serves as a precursor for steroid hormones, bile acids, and other important molecules in the body.

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Lipoprotein Density Classes

Lipoproteins are classified based on their density (g/mL). Different classes contain varying percentages of protein, cholesterol, phospholipids, and triacylglycerols.

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HDL

High-density lipoprotein; a type of lipoprotein that is thought to be a "good" type of lipoprotein because it removes bad cholesterol.

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LDL

Low-density lipoprotein; a type of lipoprotein that is thought of as a "bad" type of lipoprotein because it leads to bad cholesterol build up that can contribute to heart issues.

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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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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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