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Questions and Answers
What is the main characteristic that classifies lipids together?
Which of the following best describes saturated fatty acids?
Unsaturated fatty acids are likely to be solids at room temperature.
False
What are the two essential fatty acids mentioned?
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What do we call the type of fatty acids that have no double bonds?
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Fats and oils are triesters of glycerol and ______.
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What type of lipids are usually liquid at room temperature?
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What is the structure of simple lipids?
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Match the following fatty acids with their common names:
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What are lipids classified based on?
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What are the two types of fatty acids?
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Saturated fatty acids are likely to be liquid at room temperature.
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What is the primary structure of lipids in biological systems?
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Linoleic acid is classified as ________.
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Which fatty acid is considered omega-3?
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What are simple lipids primarily composed of?
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Saturated fatty acids pack ______ together than unsaturated fatty acids.
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What is the primary function of lipids in cell membranes?
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What do eicosanoids and steroids represent in lipids?
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Study Notes
Lipids
- A diverse group of naturally occurring compounds that share a common solubility property: insoluble in water but soluble in organic solvents like diethyl ether, dichloromethane, and acetone.
- Function as energy storage, membrane components, and chemical messengers.
Lipid Classification (Based on Function)
- Storage: Lipids store energy in the body and protect and insulate internal organs.
- Membrane Components: Lipids contribute to the formation of cell membranes, separating the cell's internal content from the aqueous environment.
- Messenger: Some lipids act as chemical messengers in the form of steroids and are found in nerve fibers.
Lipid Classification (Based on Structure)
- Simple Lipids: Esters of fatty acids with various alcohols, including fats, oils, and waxes.
- Complex Lipids: Esters of fatty acids containing additional groups besides an alcohol and a fatty acid, including phospholipids, glycolipids, lipoproteins, sulfolipids, and amino lipids.
- Derived Lipids: Include eicosanoids, steroids, fatty aldehydes, ketone bodies, lipid-soluble vitamins, and hormones.
Fatty Acids (FA)
- Long chain carboxylic acids typically consisting of 12-20 carbon atoms, usually with an even number.
- Often found in triacylglycerols (TAGs).
- Amphipathic: possess both hydrophilic (water-loving) and hydrophobic (water-repelling) sections.
Fatty Acid Types
- Saturated FA: Hydrocarbons with no double bonds, pack closely together, resulting in less fluidity and higher melting temperatures. They are likely to be solid at room temperature.
- Unsaturated FA: Hydrocarbons with one or more double bonds, do not pack as closely, resulting in higher fluidity and lower melting temperatures compared to saturated FAs. They are likely to be liquid at room temperature.
Fatty Acid Nomenclature
- Delta (Δ) Nomenclature: Uses numbers to denote the number of carbons, number of double bonds, and positions of double bonds.
- Omega (ω) Nomenclature: Carbons are counted from the methyl (omega) end. The number of carbons in the FA, number of double bonds, and number of carbons from the methyl end to the first carbon in the double bond closest to the methyl end are indicated.
Essential Fatty Acids
- The two essential fatty acids are linoleic acid (omega-6) and alpha-linolenic acid (omega-3).
- Linoleic acid: 18:2 ω 6
- Alpha-linolenic acid: 18:3 (ω 3)
Simple Lipids: Fats and Oils (Triacylglycerols/TAGs)
- Triesters of glycerol (an alcohol) and fatty acids (long chain carboxylic acids).
- Formed through dehydration reactions and hydrolyzed into 3 fatty acids and 1 glycerol.
- Fats: Usually solid at room temperature, found in meat, milk, butter, and cheese.
- Oils: Usually liquid at room temperature, primarily come from plant sources.
Lipids
- A diverse class of naturally occurring organic compounds.
- Insoluble in water but soluble in organic solvents like diethyl ether, dichloromethane, and acetone.
Classification of Lipids
-
Based on function:
- Storage: store energy and protect/insulate internal organs.
- Membrane Components: build cell membranes that separate the internal contents of cells from the surrounding aqueous environment.
- Messenger: found in nerve fibers and hormones as steroids, acting as chemical messengers.
-
Based on structure:
- Simple Lipids: esters of fatty acids with various alcohols, including fats, oils, and waxes.
- Complex Lipids: esters of fatty acids containing groups in addition to an alcohol and a fatty acid, including phospholipids, glycolipids, lipoproteins, sulfolipids, and amino lipids.
- Derived Lipids: include eicosanoids, steroids, fatty aldehydes, ketone bodies, lipid-soluble vitamins, and hormones.
Fatty Acids (FAs)
- Long-chain carboxylic acids with 12-20 carbon atoms.
- Most commonly found in triacylglycerols (TAGs).
- Amphipathic, with both hydrophilic and hydrophobic parts.
Two Types of Fatty Acids
- Saturated: Hydrocarbon chain has NO double bonds.
- Unsaturated: Hydrocarbon chain has ONE or MORE DOUBLE BONDS, with a "cis" configuration.
Impact of Saturation on Lipids
-
Saturated Fatty Acids:
- Pack close together.
- Less fluid (FAs can't move as freely).
- Higher melting temperature.
- Likely to be solids at room temperature.
-
Unsaturated Fatty Acids:
- Do NOT pack as closely.
- More fluid than saturated.
- Lower melting temperature than saturated.
- Likely to be liquid at room temperature.
Fatty Acid Nomenclature (Delta Nomenclature)
- Referred to as a system of numbers.
- of carbons: # double bonds Δx, y, z (position of double bonds)
- Example: Oleic Acid - 18:1 Δ9; Linoleic Acid - 18:2 Δ9, 12
Fatty Acid Nomenclature (Omega Nomenclature)
- Carbons are counted from the methyl (omega) end.
- Omega symbol (ω) is used instead of delta symbol.
- Includes:
- Number of carbons in the FA.
- Number of double bonds.
- Number of carbons from the methyl end to the first carbon in the double bond closest to the methyl end.
Essential Fatty Acids & Eicosanoids
- Two essential fatty acids: linoleic acid (omega-6) and alpha-linolenic acid (omega-3).
- Linoleic acid - 18:2 ω6.
- Alpha-Linolenic acid - 18:3 ω3.
Fatty Acid Nomenclature (Common Names)
- Fatty acids are almost always unbranched carboxylic acids.
- Range in size from about 10 to 20 carbons.
- Contain an even number of carbon atoms because the body builds them from acetate units.
- No other functional groups except for double bonds.
- Cis isomers are predominant in fatty acids with double bonds.
Simple Lipids: Fats and Oils (Triacylglycerols/TAGS)
- Triesters of glycerol and fatty acids.
- Formed by a dehydration reaction.
- Hydrolyzed into 3 fatty acids and 1 glycerol.
Fats vs. Oils
-
Fats:
- Solid at room temperature.
- Found in meat, whole milk, butter, and cheese.
-
Oils:
- Usually liquid at room temperature.
- Come from plant sources.
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Description
Explore the fascinating world of lipids in this quiz, which covers their classification based on function and structure. Understand the roles of storage, membrane components, and chemical messengers in biological systems. Test your knowledge on simple and complex lipids and their significance in biochemistry.
