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Questions and Answers
Which of the following is NOT a function of lipids in the body?
Which of the following is NOT a function of lipids in the body?
Which of the following is a characteristic of lipids, as defined in the text?
Which of the following is a characteristic of lipids, as defined in the text?
What is the primary chemical linkage involved in the formation of lipids?
What is the primary chemical linkage involved in the formation of lipids?
What is the approximate caloric value of lipids, per gram?
What is the approximate caloric value of lipids, per gram?
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Which of the following lipids contribute to the structure of cell membranes?
Which of the following lipids contribute to the structure of cell membranes?
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Which of the following is NOT a disease directly associated with abnormal lipid metabolism?
Which of the following is NOT a disease directly associated with abnormal lipid metabolism?
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What is the primary function of the myelin sheath?
What is the primary function of the myelin sheath?
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Which of the following is NOT a type of lipid found in the classification outlined in the text?
Which of the following is NOT a type of lipid found in the classification outlined in the text?
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Which of the following is NOT a characteristic of unsaturated fatty acids (UFA)?
Which of the following is NOT a characteristic of unsaturated fatty acids (UFA)?
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What is the main form of fat stored in the body?
What is the main form of fat stored in the body?
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Which of the following is NOT a source of triglycerides in the body?
Which of the following is NOT a source of triglycerides in the body?
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What type of reaction occurs when a fatty acid combines with glycerol to form a triglyceride?
What type of reaction occurs when a fatty acid combines with glycerol to form a triglyceride?
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Which statement regarding the structure of a triglyceride is TRUE?
Which statement regarding the structure of a triglyceride is TRUE?
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What is the general structural formula for a fatty acid?
What is the general structural formula for a fatty acid?
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What is the main reason for the increase in melting point of fatty acids as their chain length increases?
What is the main reason for the increase in melting point of fatty acids as their chain length increases?
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What is the primary reason for the rancidity in unsaturated fatty acids?
What is the primary reason for the rancidity in unsaturated fatty acids?
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What is the primary disadvantage of partially hydrogenating fats?
What is the primary disadvantage of partially hydrogenating fats?
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What is the impact of trans fats on LDL receptor activity?
What is the impact of trans fats on LDL receptor activity?
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What is the main difference between cis and trans fats?
What is the main difference between cis and trans fats?
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Which of the following is NOT a recommended strategy for reducing fat intake?
Which of the following is NOT a recommended strategy for reducing fat intake?
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What is the recommended daily intake of fat?
What is the recommended daily intake of fat?
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Which of the following acids is NOT a saturated fatty acid?
Which of the following acids is NOT a saturated fatty acid?
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What is the general formula for saturated fatty acids?
What is the general formula for saturated fatty acids?
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Which of the following statements is TRUE about unsaturated fatty acids?
Which of the following statements is TRUE about unsaturated fatty acids?
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What is the difference between omega-3 and omega-6 fatty acids?
What is the difference between omega-3 and omega-6 fatty acids?
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Which of the following fatty acids is considered essential?
Which of the following fatty acids is considered essential?
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What is the primary effect of hydrogenation on polyunsaturated fatty acids?
What is the primary effect of hydrogenation on polyunsaturated fatty acids?
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What is the main function of essential fatty acids in the body?
What is the main function of essential fatty acids in the body?
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Which of the following is NOT a function of omega-3 fatty acids?
Which of the following is NOT a function of omega-3 fatty acids?
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Flashcards
Saturated Fatty Acids (SFA)
Saturated Fatty Acids (SFA)
Fatty acids without double bonds, solid at room temperature, with a general formula of CH3-(CH2)n-COOH.
Examples of Saturated FAs
Examples of Saturated FAs
Common saturated fatty acids include acetic, butyric, palmitic, and stearic acids.
Unsaturated Fatty Acids (UFA)
Unsaturated Fatty Acids (UFA)
Fatty acids with one or more double bonds, usually liquid at room temperature.
Cis vs Trans Isomers
Cis vs Trans Isomers
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Omega-3 Fatty Acids
Omega-3 Fatty Acids
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Essential Fatty Acids
Essential Fatty Acids
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Role of Eicosanoids
Role of Eicosanoids
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Hydrogenation of PUFAs
Hydrogenation of PUFAs
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Lipids
Lipids
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Functions of Lipids
Functions of Lipids
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Triglycerides
Triglycerides
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Phospholipids
Phospholipids
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Sterols
Sterols
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Clinical Significance of Lipids
Clinical Significance of Lipids
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Simple Lipids
Simple Lipids
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Compound Lipids
Compound Lipids
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Trans Fats
Trans Fats
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Cis Fats
Cis Fats
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LDL-C
LDL-C
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Moderation in Fat Use
Moderation in Fat Use
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Hidden Fats
Hidden Fats
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Glycolipids
Glycolipids
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Fatty Acids
Fatty Acids
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Saturated Fatty Acids
Saturated Fatty Acids
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Unsaturated Fatty Acids
Unsaturated Fatty Acids
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Ester Formation
Ester Formation
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Hydrogenation
Hydrogenation
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Study Notes
Lipids Chemistry
- Lipids are heterogeneous organic substances relatively insoluble in water (hydrophobic) but soluble in organic solvents.
- Lipids consist of alcohol and fatty acids joined by ester linkage.
- Lipids have multiple functions:
- Reservoir for energy (e.g., triglycerides, 9 Kcal/g, 60% of body's energy).
- Cell membrane constituents (e.g., phospholipids, cholesterol).
- Insulators on neurons (e.g., myelin sheath).
- Protecting internal organs.
- Providing shape and contour to the body.
- Acting as emulsifiers, detergents, and emulsifying agents (e.g., lecithin, sphingomyelin, bile acid).
- Regulating metabolic processes (e.g., steroid hormones, prostaglandins).
- Contributing to food flavor, aroma, and palatability.
- Protection against external heat changes.
- Absorption of fat-soluble vitamins.
- Clinical significance of abnormal lipid metabolism includes:
- Obesity
- Atherosclerosis
- Hyperlipidemia/hypercholesterolemia
- Diabetes mellitus
- Fatty liver
- Lipid storage diseases (e.g., Gauchers, Niemann-Pick, Fabry's, and Tay-Sach's diseases).
Classification of Lipids
- Simple lipids: esters of fatty acids with alcohols (e.g., triglycerides & waxes).
- Compound lipids: esters of fatty acids with alcohols and functional groups (e.g., phospholipids, glycolipids).
- Derived lipids: steroids, cholesterol, PGs, and leukotrienes.
Simple and Compound Lipids
- Simple lipids:
- Triacylglycerol/triglycerides/neutral fats
- Waxes: esters of FA with alcohol
- Compound lipids:
- Phospholipids:
- Nitrogen-containing phospholipids: lecithin, cephalin, phosphatidyl serine
- Non-nitrogen-containing phospholipids: phosphatidyl inositol, phosphatidyl glycerol, cardiolipin (diphosphatidyl glycerol)
- Plasmalogens: lipids with long chain alcohol (e.g. choline & ethanolamine).
- Sphingomyelin
- Glycolipids: (e.g. cerebrosides, globosides, gangliosides)
- Sulpholipids: (e.g. Sulphated glycolipids)
- Phospholipids:
Derived Lipids
- Steroids (e.g., cholesterol, prostaglandins, leukotrienes, terpenes)
- Lipids conjugated with other compounds (e.g., lipoproteins, glycolipids).
Examples of Lipids
- Triglycerides
- Phospholipids
- Steroids (cholesterol)
Triglycerides
- Esters of fatty acids with alcohol
- Predominant form of fat in food and major fuel store in the body (90% of dietary intake).
- Composed of 3 fatty acids + glycerol.
- Triglyceride structure formation involves condensation reactions.
Fatty Acids
- Organic acids with chains of carbons, hydrogen, and an acid group at one end and a methyl group at the other end.
- Exist as esters on different classes of lipids.
- In humans, FFAs are formed only during metabolism.
- General structure is R--COOH
Properties of FA
- Hydrogenation: Unsaturated FAs can be converted to saturated FAs.
- Halogenation: Unsaturated FAs react with halogens.
- Melting point: Increases with increased chain length
- Short/medium-chain FAs have lower melting points than long-chain FAs.
- Salt formation: FAs and SFA can form salts (soaps) with Na, K, Ca, or Mg.
- Ester formation: UFA & SFA react with alcohol (e.g., glycerol) to form esters: glycerol+FA=monoacylglycerol; monoacylglycerol+FA=diacylglycerol; diacylglycerol+FA=triacylglycerol.
- Oxidation: FAs can oxidize forming energy in beta-oxidation.
Classifications of Fatty Acids (FAs)
- Depending on the total number of carbon atoms: Even-chain FAs (C2, C4, …) vs. Odd-chain FAs (C3, C5, …).
- Depending on the length of hydrocarbon chain: Short-chain (C2-C6), medium-chain (C8-C14), long-chain (C16-C22), very long-chain (>C24).
- Depending on the nature of the hydrocarbon chain:
- Saturated FAs (no double bonds): (e.g., acetic, butyric, palmitic, stearic, arachidic acids).
- Unsaturated FAs (one or more double bonds):
- Mono-unsaturated (one double bond) (e.g., palmitoleic, oleic).
- Poly-unsaturated (more than one double bond) (e.g., linoleic, α-linolenic, arachidonic).
- Branched-chain FAs
- Hydroxy FAs
Common Fatty Acids and Their Characteristics
- Lists various FAs (even-chain, saturated and unsaturated).
- Includes examples of food sources.
Unsaturated Fatty Acids (UFAs)
- Contain double bonds (C=C).
- Usually liquids at room temperature, becoming more fluid with increased C=C bonds.
- Naturally exist primarily as cis-isomers, but trans-isomers may form during metabolism.
- Types: MUFA (e.g., oleic acid) and PUFA (e.g., linoleic acid, linolenic acid, arachidonic acid), omega-3 and omega-6
Omega-3 and Omega-6 Fatty Acids
- Omega numbering refers to the location of the first double bond from the methyl end of the carbon chain.
- Essential fatty acids (EFAs) cannot be synthesized by the body and must be obtained from the diet. Omega-3 and omega-6 are essential fatty acids.
Essential Fatty Acids
- Linoleic and linolenic acids are essential because the body cannot synthesize them.
- Arachidonic acid is semi-essential, becoming essential when its precursor (linoleic/omega-6) is not provided.
- Functions of EFAs include:
- Cell membrane components.
- Eicosanoid synthesis (hormone-like chemicals).
Sources of Omega Fatty Acids
- Tables listing common food sources of omega-6 and omega-3 fatty acids including vegetable oils, nuts, seeds, meats, poultry, eggs, fish, etc.
Hydrogenation of PUFA
- Hydrogenation of UFAs creates more chemically stable fats with increased food shelf life, useful in food processing (margarine, peanut butter, baked goods).
- The downside is the creation of trans fats leading to health issues.
Cis vs Trans Fats
- Cis fats have hydrogens on the same side of the double bond and typically appear more bent
- Trans fats have hydrogens on the opposite side of the bond and are straighter or linear in form.
Major Sources of Various Fatty Acids
- Tables listing healthy fats with their sources.
Harmful Fatty Acids
- Lists common sources of saturated and trans fats.
Phospholipids
- Specialized form of compound lipids consisting of fatty acids, glycerol, and phosphorylated nitrogen bases (e.g., serine, ethanolamine, choline, inositol, sphingosine).
- Amphipathic nature allows for formation of lipid bilayers.
- Types include phosphoglycerides (e.g., phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, cardiolipin), phosphoinositides, and phosphosphingosides (e.g., sphingomyelin).
Phosphoglycerides
- Major phospholipids in cell membranes.
- Contain two fatty acids esterified to the first and second hydroxyl groups of glycerol (1st and 2nd OH groups).
- The third hydroxyl group (OH) forms an ester bond with phosphate.
- Subtypes: lecithin, cephalins, plasmalogen
Plasmalogens
- Structurally related to lecithins and cephalins, differing in one of the fatty acids which is replaced by an unsaturated alkyl ether linkage.
- Found in brain and muscle tissue.
Phosphoinositides
- Phosphatidylinositol (PI)
- Involves inositol as part of the structure instead of ethanolamine or choline.
Phosphosphingosides (sphingomyelins)
- Backbones of sphingomyelin is sphingosine, not glycerol.
- Fatty acids common in sphingomyelin include palmitic, stearic, lignoceric, and nervonic acid.
- Important constituent of myelin sheaths in nerve fibers.
Glycolipids
- Contain both carbohydrate and lipid components.
- Derivatives of ceramides (long-chain fatty acid attached to sphingosine)
- Types: cerebrosides, gangliosides, and acidic glycosphingolipids (e.g., sulfatides).
Cerebrosides
- Simplest type of neutral glycosphingolipid, consisting of one or more carbohydrate units (e.g., galactose or glucose).
- Important constituent of brain tissue.
- Deficiency of glucocerebrosidase results in Gaucher's disease.
Gangliosides
- Contain complex carbohydrate units and sialic acid (N-acetylneuraminic acid).
- Important constituent of membrane lipids in brain tissue.
- Act as receptors for pathogens.
Structure of Glycosphingolipids
- Glycosphingo lipids differ from sphingomyelin as they do not contain phosphate, using a monosaccharide or oligosaccharide attached to the ceramide in an O-glycosidic bond instead of a phosphate group
Sterols
- Lipids possessing multiple cyclic carbon rings, including cholesterol, Vitamin D, Sex hormones, and bile acids.
Cholesterol
- A crucial sterol.
- It is synthesized by the liver among other tissues, making it an endogenous source.
- Important component of cell membranes affecting fluidity and permeability.
- Precursor to steroid hormones, bile acids, and Vitamin D.
Sources of Cholesterol
- Includes endogenous sources (liver, adrenal cortex, gonads, skin, and intestine) and exogenous sources (diet).
Functions of Cholesterol
- Important membrane component influencing fluidity and permeability
- Precursor to steroids (steroid hormones, bile acids, Vitamin D)
Lipoproteins
- Transport hydrophobic lipids in the bloodstream.
- Types include HDL, LDL, VLDL, and chylomicrons.
- Each type has a specific density, diameter, protein composition, and lipid content.
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Description
Test your knowledge on the functions, characteristics, and structures of lipids in the body. This quiz covers key topics including lipid metabolism, triglycerides, and the role of lipids in cellular structures. Perfect for students studying biochemistry or related fields.