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BIOCHEM
MID-CHAP21
| Question | Answer |
|---|---|
| are a heterogeneous group of compounds | lipidS |
| lipids are a heterogeneous group of compounds, includING;; | fats, oils, steroids, waxes, and related compounds, that are related more by their physical than by their chemical properties |
| common property of being of LIPIDS | 1. relatively insoluBLE IN WATER 2. SOLUBLE IN NONPOLAR SOLVENTS |
| lipids are important dietary constituents not only because of the high energy value of fats but also because | essential fatty acids, fat-soluble vitamins, and other lipophilic micronutrients are contained in the fat of natural foods |
| Dietary supplementation with long-chain ω3 fatty acids is believed to have beneficial effects in a number of | chronic diseases |
| Dietary supplementation with long-chain ω3 fatty acids is believed to have beneficial effects in a number of chronic diseases, including CRD | cardiovascular disease, rheumatoid arthritis, and dementia |
| Fat is stored in | adipose tissue |
| where it also serves as a thermal insulator in the subcutaneous tissues and around certain organs. | Fat is stored in adipose tissue, |
| Nonpolar lipids act as | electrical insulators, |
| Nonpolar lipids act as electrical insulators, allowing rapid propagation of depolarization waves along ? | myelinated NERVES |
| Lipids are transported in the blood combined with proteins in | lipo-proteins particles |
| knowledge of lipid biochemistry is necessary for the understanding of many important biomedical conditions, including ?? DOMA | obesity, diabetes mellitus, and atherosclerosis |
| LIPIDS ARE CLASSIFIED AS SIMPLE OR COMPLEX | TRUE |
| include fats and waxes which are esters of fatty acids with various alcohols: | Simple lipids |
| Simple lipids// Esters of fatty acids with glycerol. | Fats: |
| Simple lipids// Esters of fatty acids with higher molecular weight monohydric alcohols. | Waxes |
| Simple lipids// are fats in The liquid state. | Oils |
| are esters of fatty acids, which always contain an alcohol and one or more fatty acids, but which also have other groups. | Complex lipids |
| Complex lipids can be divided into three types: | a. Phospholipids: b. Glycolipids (glycosphingolipids): c. Other complex lipids: |
| Contain a phosphoric acid residue. They frequently have nitrogen-containing bases (eg, choline) and other substituents. In many phospholipids the alcohol is glycerol (glycerophospholipids), | Phospholipids: |
| Contain a fatty acid, sphingosine, and carbohydrate | Glycolipids (glycosphingolipids): |
| These include lipids such as sulfolipids and amino lipids. Lipoproteins may also be placed in this category | Other complex lipids: |
| are formed from the hydrolysis of both SIMPLE and COMPLEX LIPIDS. | Derived lipids |
| Derived lipids include | fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, ketone bodies ), hydrocarbons, lipid-soluble vitamins and micronutrients, and hormones. S |
| Some of these (eg, free fatty acids, glycerol) also act as ?? in the formation of simple and complex lipids. | precursor lipids |
| Because they are UNCHARGED, acylglycerols (glycerides), cholesterol, and cholesteryl esters are termed ?? | neutral lipids |
| UNCHARGED LIPIDS | acylglycerols (glycerides), cholesterol, and cholesteryl esters |
| Fatty acids occur in the body mainly as esters in natural fats and oils, but are found in the unesterified form as | free fatty ACIDS |
| saturated | d (containing no double bonds) |
| unsaturated | (containing one or more double bonds) |
| Fatty Acids Are Named After Corresponding Hydrocarbons | TRUE |
| Saturated Fatty Acids Contain No Double Bonds | TRUE |
| Contain No Double Bonds | Saturated Fatty Acids |
| Saturated fatty acids may be envisaged as based on acetic acid | (CH3—COOH) |
| Unsaturated Fatty Acids Contain One or More Double Bonds | TRUE |
| Contain One or More Double Bonds | Unsaturated Fatty Acids |
| containing one double bond. | Monounsaturated (monoethenoid, monoenoic) acids, |
| containing two or more double bond | Polyunsaturated (polyethenoid, polyenoic) acids |
| These compounds, derived from eicosa (20-carbon) polyenoic fatty acids | Eicosanoids |
| (LTs) | leukotrienes |
| (LXs) | lipoxins |
| (PGs), | prostaglandins |
| (PGIs) | prostacyclins |
| (TXs) | thromboxanes |
| comprise the prostanoids, leukotrienes (LTs), and lipoxins (LXs). Prostanoids include prostaglandins (PGs), prostacyclins (PGIs), and thromboxanes (TXs). | Eicosanoids: |
| exist in VIRTUALLY every mammalian tissue, acting as local hormones; they have important physiologic and pharmacologic activities. | Prostaglandins |
| have the cyclopentane ring interrupted with an oxygen atom (oxane ring) | thromboxanes |
| are a third group of eicosanoid derivatives formed via the lipoxygenase pathway | leukotrienes and lipoxins |
| Leukotrienes cause bronchoconstriction as well as being potent proinflammatory agents, and play a part in | asthma |
| Most Naturally Occurring Unsaturated Fatty Acids Have cis Double Bonds | TRUE |
| occurs in unsaturated fatty acids, depending on the orientation of atoms or groups around the axes of double bonds, which do not allow rotation. | geometric isomerism |
| are present in certain foods, arising as a by-product of the saturation of fatty acids during hydrogenation, or “hardening,” of natural oils in the manufacture of margarine. | Trans fatty acids |
| Physical and Physiologic Properties of Fatty Acids Reflect Chain Length and Degree of Unsaturation | TRUE |
| A triacylglycerol containing three saturated fatty acids of 12 or more carbons is ?? at body temperature, | solid |
| if the fatty acid residues are polyunsaturated, it is ? to below 0°C. I | liquid |
| ω3 Fatty Acids Are Anti-Inflammatory and Have Health Benefits | TRUE |
| (found in plant oils) | s α-linolenic (ALA) |
| (found in fish oil), | eicosapentaenoic (EPA) |
| (found in fish and algal oils) | docosahexaenoic (DHA) |
| Current evidence suggests that diets rich in ω3 fatty acids are beneficial, particularly for cardiovascular disease, but also for other chronic degenerative diseases such as | cancer, rheumatoid arthritis, and Alzheimer disease. |
| TRIACYLGLYCEROLS (TRIGLYCERIDES)* ARE THE MAIN STORAGE FORMS OF FATTY ACIDS | TRUE |
| ARE THE MAIN LIPID CONSTITUENTS OF MEMBRANES | PHOSPHOLIPIDS |
| Many phospholipids are derivatives of | phosphatidic acid |
| is important as an intermediate in the synthesis of triacylglycerols as well as phosphoglycerols | Phosphatidic acid |
| Sphingolipids, such as ?? in which the phosphate is esterified to sphingosine, a complex amino alcohol | sphingomyelin, |
| is important in nervous transmission, as acetycholine, and as a store of labile methyl groups. | Choline |
| is a very effective surface-active agent and a major constituent of the surfactant preventing adherence, | Dipalmitoyl lecithin |
| absence OF Dipalmitoyl lecithin from the lungs of premature infants causes | respiratory distress syndrome |
| Most phospholipids have a saturated acyl radical in the sn-1 position but an unsaturated radical in the sn-2 position of glycerol. | TRUE |
| (cephalin) | Phosphatidylethanolamine |
| programmed cell death) | apopTOSIS |
| are found in the outer leaflet of the cell membrane lipid bilayer and are particularly abundant in specialized areas of the plasma membrane known as lipid rafts | Sphingomyelins |
| known as lipid rafts | plasma membrane |
| They are also found in large quantities in the MYELIN sheath that surrounds nerve fibers. | Sphingomyelins |
| They are believed to play a role in cell signaling and in apoptosis. S | Sphingomyelins |
| contain no glycerol, and on hydrolysis they yield a fatty acid, phosphoric acid, choline, and sphingosine | Sphingomyelins |
| The combination of sphingosine plus fatty acid is known as | ceramide |
| a structure also found in the glycosphingolipids | ceramide |
| Phosphatidylinositol Is a Precursor of Second Messengers | TRUE |
| The ?? is present in phosphatidylinositol as the stereoisomer, myoinositol | inositol |
| are minor components of cell membranes, but play an important part in cell signaling and membrane trafficking. | Phosphorylated phosphatidylinositols (phosphoinositides) |
| Is a Major Lipid of Mitochondrial Membranes | Cardiolipin |
| is a precursor of phosphatidylglycerol, which in turn gives rise to cardiolipin | Phosphatidic acid |
| This phospholipid is found only in mitochondria and is essential for the mitochondrial function. | Phosphatidic acid |
| (cardioskeletal myopathy). | Barth syndrome |
| Lysophospholipids Are Intermediates in the | Metabolism of Phosphoglycerols |
| Plasmalogens Occur in ? | Brain & Muscle |
| lysophosphatidylcholine (lysolecithin) is also found in oxidized lipoproteins and has been implicated in some of their effects in promoting | atherosclerosis. |
| ARE IMPORTANT IN NERVE TISSUES & IN THE CELL MEMBRANE | GLYCOLIPIDS (GLYCOSPHINGOLIPIDS) |
| are lipids with an attached carbohydrate or carbohydrate chain. | Glycolipids |
| They occur particularly in the outer leaflet of the plasma membrane, where they contribute to cell surface carbohydrates which form the glycocalyx | Glycolipids |
| The major glycolipids found in animal tissues are | glycosphingolipids |
| They contain ceramide and one or more sugars | glycosphingolipids |
| glycosphingolipids Contain ceramide and one or more | sugars |
| is a major glycosphingolipid of brain and other nervous tissue, found in relatively low amounts elsewhere. | Galactosylceramide |
| It contains a number of characteristic C24 fatty acids, for example, cerebronic acid. | Galactosylceramide |
| Galactosylceramide can be converted to | sulfogalactosylceramide (sulfatide) |
| h has a sulfo group attached to the O in the three position of galactose and is present in high amounts in myelin | sulfogalactosylceramide (sulfatide) |
| resembles galactosylceramide, but the head group is glucose rather than galactose | Glucosylceramide |
| are complex glycosphingolipids derived from glucosylceramide that contain in addition one or more molecules of a sialic acid. | Gangliosides |
| is the principal sialic acid found in human tissues. Gangliosides are also present in nervous tissues in high concentration | Neuraminic acid |
| . They function in cell–cell recognition and communication and as receptors for hormones and bacterial toxins such as cholera toxin | Neuraminic acid |
| . The simplest ganglioside found in tissues is ?? which contains ceramide, one molecule of glucose, one molecule of galactose, and one molecule of NeuAc. | GM3 , |
| In the shorthand nomenclature used, G represents | ganglioside |
| In the shorthand nomenclature used, M represents | monosialo-containing species |
| In the shorthand nomenclature used, the subscript 3 represents | a number assigned on the basis of chromatographic migration |
| GM3 , is of considerable biologic interest, as it is known to be the receptor in human intestine for | cholera toxin. |
| ?? probably best known by most people for its association with atherosclerosis and heart disease, it has many essential roles in the body | cholesterol |
| It is the precursor of a large number of equally important steroids that include the bile acids, adrenocortical hormones, sex hormones, vitamin D and cardiac glycosides. | cholesterol |
| All steroids have a similar cyclic nucleus resembling phenanthrene .. to which a cyclopentane ring (D) is attached | (rings A, B, and C) |
| Because of Asymmetry in the Steroid Molecule, Many Stereoisomers Are Possible | TRUE |
| Because of Asymmetry in the Steroid Molecule, Many Stereoisomers Are | Possible |
| Each of the six-carbon rings of the steroid nucleus is capable of existing in the three-dimensional conformation either of a | chair” or a “boat” |
| In naturally occurring steroids, virtually all the rings are in the ?? FORM .. which is the more stable conformation. | “chair” |
| The junction between the A and B rings may be cis or trans in naturally occurring steroids. | TRUE |
| Cholesterol Is a Significant Constituent of Many Tissues | TRUE |
| It is a major constituent of the plasma membrane and of plasma lipoproteins | Cholesterol |
| It is often found as cholesteryl ester, where the hydroxyl group on position 3 is esterified with a long-chain fatty acid. | Cholesterol |
| It occurs in animals but not in plants or bacteria. | Cholesterol |
| Ergosterol Is a Precursor of | Vitamin D |
| Ergosterol Is a Precursor of Vitamin D | TRUE |
| occurs in plants and yeast and is important as a dietary source of vitamin D | Ergosterol |
| Polyprenoids Share the Same Parent Compound as Cholesterol | TRUE |
| are not steroids but are related to them because they are synthesized, like cholesterol | Polyprenoids |
| participates in the respiratory chain in mitochondria and the long-chain alcohol dolichol | ubiquinone |
| takes part in glycoprotein synthesis by transferring carbohydrate residues to asparagine residues of the polypeptide | dolichol |
| Plant-derived polyprenoids include | rubber, camphor, the fat-soluble vitamins A, D, E, and K, and β-carotene (provitamin A). |
| LIPID PEROXIDATION IS A SOURCE OF FREE RADICALS | TRUE |
| of lipids exposed to oxygen is responsible not only for deterioration of foods (rancidity), but also for damage to tissues in vivo, where it may be a cause of cancer, inflammatory diseases, atherosclerosis, and aging. | Peroxidation (auto-oxidation) |
| The deleterious effects are considered to be caused by | free radicals |
| Free radicals containing oxygen (eg, ROO•, RO•, OH•) are termed | reactive oxygen species (ROS) |
| is a chain reaction in which free radicals formed in the initiation stage in turn generate more (propagation), and thus it has potentially devastating effects. | Lipid peroxidation |
| ROOH + Metal(n)+ → ROO• + Metal(n-1)+ + H+ X• + RH → R• + XH | Initiation: process |
| R•+ O2 → ROO•ROO•+ RH → ROOH + R•, etc | Propagation: process |
| ROO• + ROO•→ ROOR + O2ROO•+ R•→ ROORR•+ R•→ RR | Termination: process |
| are used to control and reduce lipid peroxidation, both by humans in their activities and in nature. | Antioxidants |
| are antioxidants used as food additives. | Propyl gallate, butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) |
| Naturally occurring antioxidants include vitamin E or ,, which is lipid soluble | (tocopherol) |
| which are water soluble | urate and vitamin C, |
| is an antioxidant at low PO2 . | β-Carotene |
| Antioxidants fall into two classes: | 1. preventive antioxidants, 2. chain-breaking antioxidants |
| reduce the rate of chain initiation | preventive antioxidants, |
| interfere with chain propagation | chain-breaking antioxidants |
| include catalase and other peroxidases such as glutathione peroxidase ,, that react with ROOH; selenium, which is an essential component of glutathione peroxidase and regulates its activity, and chelators of metal ions such as (EDTA) and(DTPA). | preventive antioxidants, |
| In ?? the principal chain-breaking antioxidants are superoxide dismutase, | vivo, |
| Peroxidation is also catalyzed in vivo by heme compounds and by ?? ,, found in platelets and leukocytes | lipoxygenases |
| (formed from cholesterol) | oxysterols |
| (formed from the peroxidation of polyunsaturated fatty acids such as arachidonic acid) | isoprostanes |
| lipids are insoluble in water since they contain a predominance of nonpolar (hydrocarbon) groups | true |
| or water insoluble | hydrophobic |
| or water soluble | hydrophilic, |
| They become oriented at oilwater interfaces with the polar group in the water phase and the nonpolar group in the oil phase | amphipathic |
| When a critical concentration of these lipids is present in an aqueous medium, they form | micelles. |
| s are much larger particles, formed usually by nonpolar lipids in an aqueous medium. These are stabilized by emulsifying agents such as amphipathic lipids | Emulsions |
| form a surface layer separating the main bulk of the nonpolar material from the aqueous phase | phosphatidylcholine// Emulsions |
| Eicosanoids are formed from how many carbon polyunsaturated fatty acids | 20 |
| triacylglycerol means | (“fat”) |
| a major constituent of some lipoprotein classes and the storage form of lipid | triacylglycerol (“fat”), |
| , an amphipathic lipid, is an important component of membranes. | Cholesterol |
| It is the parent molecule from which all other steroids in the body, including major hormones such as the adrenocortical and sex hormones, D vitamins, and bile acids, are synthesized. | Cholesterol |
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