Biochemistry of Lipids Quiz
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Questions and Answers

What characteristic primarily defines lipids?

  • Formation of peptide bonds
  • Presence of amino acids
  • High solubility in water
  • High solubility in nonpolar solvents (correct)

Which of the following classifications of lipids includes molecules that contain isoprene units?

  • Phospholipids
  • Triacylglycerols
  • Isoprenoids (correct)
  • Fatty acids

What type of fatty acid has only single carbon-carbon bonds?

  • Polyunsaturated
  • Saturated (correct)
  • Trans
  • Monounsaturated

What is the melting point of arachidonic acid?

<p>-49 ºC (C)</p> Signup and view all the answers

What structural feature allows lipid membranes to act as effective barriers to polar molecules?

<p>Hydrophobic nature of lipid molecules (D)</p> Signup and view all the answers

Which fatty acid is essential and must be obtained from the diet?

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

How many carbon atoms do most naturally occurring fatty acids have?

<p>14 to 24 (B)</p> Signup and view all the answers

Which of the following fatty acids is considered saturated?

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

Which term describes fatty acids that have one or more double bonds in their hydrocarbon chain?

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

Which unsaturated fatty acid is the most common in nature?

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

What is produced during the hydrolysis of triglycerols in a process called saponification?

<p>Salt of free fatty acids and glycerol (D)</p> Signup and view all the answers

Which fatty acid has the highest melting point among those listed?

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

What distinguishes monounsaturated fatty acids from polyunsaturated fatty acids?

<p>Mono has one double bond, poly has two or more (D)</p> Signup and view all the answers

What are triacylglycerols primarily used for in animals?

<p>Storing energy as body fat (B)</p> Signup and view all the answers

Among the following, which characteristic is not typical of unsaturated fatty acids?

<p>Have a greater tendency to solidify at room temperature (B)</p> Signup and view all the answers

Which of the following describes branched-chain fatty acids found in microorganisms?

<p>They include tuberculostearic acid. (D)</p> Signup and view all the answers

What is the primary historical use of soap during the time of Hippocrates?

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

Which of the following describes a phosphoglyceride?

<p>A 1,2-diacylglycerol with a phosphate group esterified at carbon atom 3 (C)</p> Signup and view all the answers

Which lipid is described as commonly found in biological membranes and is rich in highly reduced carbons?

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

What is the correct interpretation of glycerophospholipid nomenclature?

<p>The number 2 carbon can represent D- or L-isomers (D)</p> Signup and view all the answers

What is cardiolipin primarily known for?

<p>First observed in heart tissue (C)</p> Signup and view all the answers

What is a notable feature of phosphatidic acid?

<p>It serves as an important intermediate in glycerophospholipid biosynthesis (D)</p> Signup and view all the answers

Which of the following BEST describes sphingolipids?

<p>They are a complex class of different lipids found in biological membranes (D)</p> Signup and view all the answers

What contributes to the energy yield difference between triacylglycerols and carbohydrates?

<p>The number of reduced carbons in triacylglycerols (D)</p> Signup and view all the answers

What forms the backbone of glycosphingolipids?

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

What characterizes a cerebroside in glycosphingolipids?

<p>It contains only neutral sugar residues. (B)</p> Signup and view all the answers

What happens when a sulfate is esterified at the 3-position of galactose?

<p>It becomes a sulfatide. (B)</p> Signup and view all the answers

What role do gangliosides play in the body?

<p>They are involved in nerve impulse transmission. (B)</p> Signup and view all the answers

What is the primary feature of waxes?

<p>They are esters of long-chain alcohols with long-chain fatty acids. (A)</p> Signup and view all the answers

Which type of terpene consists of four isoprene units?

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

Why are waxes generally water-insoluble?

<p>They have a weakly polar head group and a nonpolar tail. (D)</p> Signup and view all the answers

What incorrect statement could be made about monoterpenes?

<p>They contain more than four isoprene units. (A)</p> Signup and view all the answers

Flashcards

Lipids: Definition

Lipids are biological molecules that are poorly soluble in water but highly soluble in nonpolar solvents, typically made of hydrocarbons.

Fatty Acid Structure

A fatty acid consists of a long hydrocarbon chain (tail) with a carboxyl group (head).

Saturated vs. Unsaturated Fatty Acids

Saturated fatty acids have only single bonds between carbon atoms, while unsaturated fatty acids have one or more double bonds.

Fatty Acid Naming

Fatty acids can be named by the number of carbon atoms and the location of double bonds in their chains

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Triacylglycerols

Lipids formed from glycerol and three fatty acids, often used for energy storage.

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Amphipathic Lipids

Lipids with both polar and nonpolar regions.

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Isoprenoids

Lipids constructed from repeating isoprene units.

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Lipid Solubility

Lipids are more soluble in nonpolar solvents than in water.

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Saturated Fatty Acids

Fatty acids with no double bonds between carbon atoms.

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Unsaturated Fatty Acids

Fatty acids with one or more double bonds between carbon atoms

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Essential Fatty Acids

Fatty acids humans cannot synthesize and must obtain from their diet

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Triglycerides

Energy storage molecules made of glycerol and three fatty acids.

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Simple Triglyceride

Triglyceride with three identical fatty acid chains.

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Mixed Triglyceride

Triglyceride with two or three different fatty acids.

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Saponification

The process of breaking down fats using alkali, producing salts and glycerol.

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Adipose tissue

Body tissue that stores lipids (fats).

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What is soap?

Soap is a mixture of salts of fatty acids, traditionally made by saponifying fats or oils with a strong alkali, such as lye (sodium hydroxide) or potassium hydroxide.

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What is a glycerophospholipid?

A glycerophospholipid is a type of phospholipid that is built from glycerol and two fatty acids, along with a phosphate group attached to the third carbon of glycerol.

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What is the function of glycerophospholipids?

Glycerophospholipids are essential components of cell membranes, contributing to their structure and function.

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Cardiolipin

Cardiolipin is a specialized type of glycerophospholipid with two phosphatidylglycerol molecules linked together. It is particularly abundant in the inner mitochondrial membrane.

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What is a sphingolipid?

A sphingolipid is a type of lipid that is built from the long-chain amino alcohol sphingosine, a fatty acid, and a head group.

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What is phosphatidic acid?

A simple glycerophospholipid that serves as a precursor in the biosynthesis of other glycerophospholipids.

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Lecithin

Lecithin is a type of glycerophospholipid with choline as the head group. Found in cell membranes and used in food products as an emulsifier.

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What are the major functions of lipids?

Lipids serve as a source of energy, building blocks for cell membranes, signaling molecules, and insulation.

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Sphingolipids

Lipids with a sphingosine backbone instead of glycerol, forming the basis for glycosphingolipids and other complex lipids.

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Glycosphingolipids

Ceramides with one or more sugar residues linked to the 1-hydroxyl moiety, forming neutral or charged structures.

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Cerebroside

A glycosphingolipid with a single glucose or galactose attached, a simple type of glycosphingolipid.

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Sulfatide

A glycosphingolipid with a sulfate group attached to the galactose residue.

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Ganglioside

A complex glycosphingolipid with three or more sugars, including a sialic acid, important for nerve function.

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Waxes

Esters of long-chain alcohols and fatty acids, highly water-repellant due to long hydrocarbon chains.

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Terpenes

Lipids built from isoprene units (C5), forming various structures like monoterpenes, sesquiterpenes, etc.

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Isoprene Unit

A five-carbon unit (C5) that forms the basis of terpenes and related compounds.

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Study Notes

Lipids

  • Lipids are a class of biological molecules defined by their low solubility in water and high solubility in nonpolar solvents.
  • Lipids are primarily hydrocarbons.
  • Upon oxidation in metabolism, lipids yield large amounts of energy for metabolic energy storage.
  • Lipids found in biological systems are either hydrophobic or amphipathic.
  • Amphipathic molecules possess both polar and nonpolar groups.

Classification of Lipids

  • Fatty acids and derivatives
  • Triacylglycerols
  • Wax esters
  • Phospholipids (Phosphoglycerides and sphingomyelin)
  • Sphingolipids (other than sphingomyelin, those containing sphingosine)
  • Isoprenoids (molecules made up of multiple copies of isoprene)

Fatty Acids

  • A fatty acid is composed of a long hydrocarbon chain ("tail") and a terminal carboxyl group ("head").
  • The carboxyl group is typically ionized under physiological conditions.
  • Most fatty acids in nature have an even number of carbon atoms (usually 14 to 24).
  • Fatty acids are either saturated or unsaturated.
  • Saturated fatty acids have only single carbon-carbon bonds.
  • Unsaturated fatty acids have one or more double bonds in their hydrocarbon chain.
  • Monounsaturated fatty acids have a single double bond.
  • Polyunsaturated fatty acids have more than one double bond.
  • Most double bonds of fatty acids in nature are in the cis conformation.
  • Saturated fatty acids are typically straight-chain, while the cis-unsaturated fatty acids have bends in the chain.

Saturated Fatty Acids

-Lauric acid (12:0), melting point 45°C -Myristic acid (14:0), melting point 55°C -Palmitic acid (16:0), melting point 63°C -Stearic acid (18:0), melting point 69 °C -Arachidic acid (20:0), melting point 76 °C

Unsaturated Fatty Acids

-Palmitoleic acid (16:1), melting point 0°C -Oleic acid (18:1), melting point 13°C -Linoleic acid (18:2), melting point -5°C -Linolenic acid (18:3), melting point -11°C -Arachidonic acid (20:4), melting point -49°C

Triglycerols

  • Also called triglycerides.
  • Are a major energy reserve and principal neutral derivatives of glycerol found in animals.
  • Molecules consist of a glycerol esterified with three fatty acids.
  • If all three fatty acid groups are the same, the molecule is called a simple triacylglycerol (e.g., tristearin, triolein).
  • Mixed triacylglycerols contain two or three different fatty acids.
  • Triacylglycerols are primarily found in adipose tissue (body fat), which serves as a storage site for lipids.

Phospholipids

  • Are a 1,2-diacylglycerol with a phosphate group esterified at carbon atom 3 of the glycerol backbone.
  • Also known as phosphoglycerides or glycerolphosphatides.
  • Essential components of cell membranes and are found in small concentrations in other parts of the cell.
  • All glycerophospholipids are members of the broader class of lipids known as phospholipids.
  • The numbering and nomenclature of glycerophospholipids present a dilemma.
  • The number 2 carbon of the glycerol backbone of a phospholipid is asymmetric.

Sphingolipids

  • An 18-carbon amino alcohol, sphingosine, forms the backbone of these lipids rather than glycerol.
  • Several types include sphingomyelin, cerebroside, and ganglioside.

Glycosphingolipids

- Consist of a ceramide with one or more sugar residues in a glycosidic linkage at the 1-hydroxyl moiety.
- Neutral glycosphingolipids contain only neutral (uncharged) sugar residues
- Cerebroside is a molecule with single glucose or galactose attached.

Gangliosides

  • Another class of lipids formed when a sulfate is esterified at the 3-position of the galactose.
  • More complex glycosphingolipids that consist of a ceramide backbone with three or more sugars esterified.
  • One of these sugars is a sialic acid (such as N-acetylneuraminic acid).

Waxes

  • Esters of long-chain alcohols with long-chain fatty acids.
  • Water-repellant, character to animal skin, leaves of plants, bird feathers, and glossy surface of polished apples.

Terpenes

  • A class of lipids formed from combinations of two or more molecules of isoprene (a five-carbon unit).
  • Monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), triterpenes (C30), and tetraterpenes (C40).
  • Examples include limonene, citronellal, menthol, bisabolene, phytol, gibberellic acid, and all-trans-retinal.

Other Lipids

  • Vitamin E (α-tocopherol), Vitamin K (phylloquinone, phylloquinones)
  • Coenzyme Q (Ubiquinone, UQ)
  • Dolichol phosphate.

Additional Information

  • Polar bears use triacylglycerols to survive long periods of fasting.
  • Snake venom contains phospholipases which can breakdown phospholipids.

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Lesson 6: Structure and Function of Lipids PDF

Description

Test your knowledge on the structure, classification, and functions of lipids in biochemistry. This quiz covers essential fatty acids, triglycerides, and the physical properties of various lipids. Prepare to dive deep into the characteristics that define lipids and their significance in biological systems.

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