Ch 21 - Lipids Of Physiologic Significance Flashcards
The _______ are heteregoneous group of compounds, including FATS, OILS, STEROIDS, WAXES amd related compounds, that are related more by their physical than by their chemical properties.
Lipids
Lipids have the common property of being _________ in water and _________ in nonpolar solvents such as ETHER, CHLOROFORM and BENZENE.
Insoluble
Soluble
Dietary supplementation with _______________ is believed to have beneficial effects in a number of chronic diseases, including cardiovascular disease, rheumatoid arthritis and dementia.
Long chain omega-3 fatty acids
Nonpolar lipids acts as _____________, allowing rapid propagation of depolarization waves along myelinated nerves.
Electrical insulator
Lipids are transported in the blood combined with proteins in _________________.
Lipoprotein practicles
_______________ include FATS and WAXES which are esters of fatty acids vith various alcohols.
Simple lipids
Esters of fatty acids with GYLCEROL.
Fats
______ are fats in the liquid state.
Oils
Esters of fatty acids with higher molecular weight monohydric alcohols.
Waxes
______________ are esters of fatty acids containing groups in addition to an alcohol and one or more fatty acids.
Complex lipids
Lipids containing in addition to fatty acids and an alcohol, a phosphoric acid residue. They frequently have nitrogen-containing bases (e.g choline).
Phospholipids
In many phospholipids the alcohol is GLYCEROL ______________ but in _________________ it is SPHINGOSINE, which contains an amino group.
Glycerophospholipids
Sphingophospholipids
Lipids containing a fatty acid, sphingosine and carbohydrate.
Glycolipids (Glycosphingolipids)
Because they are uncharged, acylglycerols (glycerides), cholesterol and cholesteryl esters are termed ____________.
Neutral lipids
_______________ are alipathic carboxylic acids.
Fatty acids
Fatty acids occur in the body mainly as ________ in natural fats and oils, but are found in the unesterified form as ______________, a transport form in the plasma.
Esters
Free fatty acids
True or False:
Fatty acids that occur in natural fats usually contain an even number of carbon atoms.
True
Containing one or more double bonds.
Unsaturated
Containing no double atoms
Saturated
The most frequently used systematic nomenclature names the fatty acid after the hydrocarbon with the same number and arrangement of carbon atoms, with -_____ being substitued for the final -e. (___________ system).
-oic
Genevan system
Saturated acids end in -_____ for example OCTANOIC ACID and unsaturated acids with double bonds end in -_______ for example OCTADECENOIC ACID.
- anoic
- enoic
Carbon atoms are numbered from the ___________________.
Carboxyl carbon (carbon no. 1)
The carbon atoms adjacent to the carboxyl carbon (nos. 2, 3, 4) are also known as the _______________ respectively.
Alpha, beta and gamma carbons
The terminal methyl carbon is known as the _____________.
w-or n-carbon
Major end product of carbohydrate fermentation by rumen organisms.
Acetic
In certain fats in small amounts (especially butter). An end product of carbohydrate fermentation by rumen organisms.
Butyric
Spermaceti, cinnamon, palm kernel, coconut oils, laurels and butter.
Lauric
Nutmeg, palm kernel, coconut oils, myrtles , butter
Myristic
Common in all animal and plant fats
Palmitic
18 Carbon atoms
Stearic
16 C atoms
Palmitic
14 C atoms
Myristic
12 C atoms
Lauric
6 C atoms
Caproic
5 C atoms
Valeric
4 C atoms
Butyric
2 C atoms
Acetic
Containg one double bond.
Monounsaturated
Containing two or more double bonds.
Polyunsaturated
These compounds, derived from eicosa (20-carbon) polyenoic fatty acids comprise the PROSTANOIDS, LEUKOTRIENES (LTs), and LIPOXINS (LXs).
Eicosanoids
______________ exist in virtually every mammalian tissue, acting as local hormones; they have important physiologic and pharmacologic activites.
Prostaglandins
They are synthesized in vivo by cyclization of the center of the carbon chain of 20-carbon (eicosanoic) polyunsaturated fatty acids to form a cyclopentane ring.
Prostaglandins
The _________________ have the cyclopentane ring interrupted with an oxygen atom (oxane ring).
Thromboxanes
The LEUKOTRIENES and LIPOXINS are a third group of eicosanoid derivatives formed via the ________________.
Lipoxygenase pathway
___________________ cause bronchoconstriction as well as being potent inflammatory agents, and play a part in asthma.
Leukotrienes
Most naturally occuring unsaturated fatty acids have ___________.
cis double bounds
The carbon chains of unsaturated fatty acids form a _____________ when extended at low temperatures.
Zigzag pattern
At higher temperatures, some bonds ________, causing chain shortening, which explains why biomembranes become thinner with increases in temperature.
Rotate
A type of _______________ 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
If the acyl chains are on the SAME SIDE of the bond, it is -____ as in oleic acid; if on OPPOSITE SIDES, it is ______- as in elaidic acid.
Cis
Trans
Double bonds in naturally occuring unsaturated long-chain fatty acids are nearly all in the ____ configuration, the molecules being “bent” _____ degrees at the double bond.
Cis
120
Thus, oleic acid has a _______, whereas elaidic acid remains ____.
V shape
Straight
__________, with 4 cis double bonds, is bent into a U shape.
Arachidonic acid
True or False
DECREASE in the number of cis double bonds in a fatty acid leads to a variety of possible spatial configurations of the molecule.
False
INCREASE
____________ are presemt 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
True or False:
Physical and physiologic properties of fatty acids reflect CHAIN LENGTH and DEGREE OF UNSATURATION.
True
The melting points of even-numbered fatty acids _______ with chain length and _________ according to unsaturation.
Increase
Decrease
In nearly all fats
Palmitoleic
Possibly the most common fatty acid in natural fats; particularly high in olive oil
Oleic
Hydrogenated and ruminant fats
Elaidic
Corn, peanut, cottonseed, soy bean and many plant oils
Linoleic
Some plants, eg. oil of evening primrose, borage oil; minor fatty acid in animals
Gamma-linolenic
Found in animal fats, important component of phospholipids in animals.
Arachidonic
Important component of fish oils, eg, cod liver, mackerel, menhaden, salmon oils
Timnodonic
Fish oils, algal oils, phospholipids in brain
Cervonic
A triacylglycerol containing three saturated fatty acids of 12 carbons or more is _______ at body temperature, whereas if the fatty acid residues are polyunsaturated, it is ___________.
Solid
Liquid to below 0 degree.
____________ which must be fluid at all environmental temperature, are more unsaturated than storage lipids.
Membrane lipids
True or False
Lipids in tissues that are subject to cooling, for example, in hibernators or in the extremities of animals, are also more unsaturated.
True
Found in plant oils.
Alpha-linolenic (ALA)
Found in fish oil
Eicosapentaenoic (EPA)
Found in fish and algal oils
Docosahexaenoic (DHA)
_____________ are the main storage forms of fatty acids.
Triacylglycerols (Triglycerides)
The _____________ are esters of the trihydric alcohol and fatty acids.
Triacylglycerols
______ and _________ wherein one or two fatty acids are esterified with glycerol
Mono- and diacylglycerols
Carbon __ & __ of glycerol are not identical.
1 & 3
To number the carbon atoms of glycerol unambigously, the ___________ system is used.
-sn (stereochemical numbering)
Glycerol is always phosphorylated on sn-3 by glycerol kinase to give _____________ and not gylcerol-1-phosphate.
Gylcerol-3-phosphate
Many phospholipids are derivatives of _________________, in which the phosphate is esterified with one OH group of glycerol and the other two OH groups are esterified to two long chain fatty acids.
Phosphatidic acid
_____________ is important as an intermediate in the synthesis of triacylglycerols as well as phosphoglycerols but is not found in any great quantity in tissues.
Phosphatidic acid
____________ containing CHOLINE are the most abundant phospholipids of the cell membrane and represent a large proportiom of the body’s store of choline.
Glycerophospholipids
Commonly called LECITHINS.
Phosphatidylcholines
_______ is important in nervous transmission and as a store of labile methy groups.
Choline
___________ is a very effective surface-active agent and a major constituent of the surfactant preventing adherence, due to surface tension, of the inner surfaces of the lungs.
Dipalmitoyl lecithin
Most phospholipids have a SATURATED acyl radical in the ________ position but an UNSATURATED radical in the _____ of glycerol.
sn-1
sn-2
Phosphatidylserine also plays a role in ___________.
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 __________.
Sphingomyelins
Lipid rafts
_____________ 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.
Sphingomyelins
True or False:
Sphingomyelins contain glycerol, and on hydrolysis they yield a fatty acid, phosphoric acid, choline and sphingosine.
False:
NO GLYCEROL
The combination of sphingosine plus fatty acid is known as _________, a structure also found in the glycosphingolipids.
Ceramide
______________ is a precursor of second messengers.
Phosphatidylinositol
The inositol is present in phosphatidylinositol as the stereoisomoer, ____________.
Myoinositol
Phosphorylated phosphatidylinositols or ______________ are minor components of cell membranes but play an important part in CELL SIGNALING and MEMBRANE TRAFFICKING.
Phosphoinositides
Phosphatidylinositol 4,5-biphosphate (PiP2) is cleaved into _________ and ________ upon stimulation by a suitable hormone agonist, and both of these act as internal signals or second messengers.
Diacylglycerol and inositol tris-phosphate
___________ is a major lipid of mitochondrial membranes.
Cardiolipin
Phosphatidic acid is a precursor of phosphatidylglycerol, which in turn gives rise to ___________.
Cardiolipin
This phospholipid is found only in mitochondria and is essential for the mitochondrial function.
Cardiolipin
_________ cardiolipin levels or alterations in its structure or metabolism cause mitochondrial dysfunction in aging and in pathological conditions including HEART FAILURE, HYPOTHYROIDISM and BARTH SYNDROME (Cardioskeletal myopathy).
Decreased
___________ are intermediates in the metabolism of phosphogylcerols.
Lysophospholipids
These are phosphoacylglycerols containing only one acyl radical, for example _______________, important in the metabolism and interconversion of phospholipids.
Lysophosphatidylcholine (lysolecithin)
It is also found in oxidized lipoproteins and has been implicated in some of their effects in promoting atherosclerosis.
Lysophospholipids
These compounds constitue as much as 10% to 30% of the phospholipids of brain and heart.
Plasmalogens
Structurally, the plasmalogens resemble _______________ but posess an ether link on the sn-1 carbon instead of the ester link found in acylglycerols.
Phosphatidylethanolamine
Typically, the __________ is an unsaturated alcohol.
Alkyl radical
It has been suggested that they may have a protective effect against reactive oxygen species.
Plasmalogens
______________ are important in nerve tissues and in the cell membrane.
Glycolipids (Glycosphingolipids)
________ are lipids with an attached carbohydrate or carbohydrate chain. They are widely distributed in every tissue of the body, particularly in nervous tissue such as brain.
Glycolipids
Glycolipids occur particularly in the outer leaflet of the plasma membrane, where they contribute to cell surface carbohydrates which form the _________.
Glycocalyx
The major glycolipids found in animal tissues are _______________.
Glycosphingolipids
True or False:
Glycosphingolipids contain ceramide and one or more sugars.
True
___________ is a major glycosphingolipid of brain and other nervous tissue, found in relatively low amounts elsewhere.
Galactosylceramide
Galactsylceramide contains a number of characterstic _____ fatty acids for example, cerebronic acid.
C24
Galactosylceramide can be converted to ___________ which has a sulfo group attached to the O in the three position of galactose and is present in high amounts in ________.
Sulfogalactosylceramide (sulfatide)
Myelin
____________ resembles galactosylceramide, but the head group is GLUCOSE rather than galactose.
Glucosylceramide
It is the predominant simple glycosphingolipid of extraneural tissues, also occuring in the brain in small amounts.
Glucosylceramide
_________ are complex glycosphingolipids are 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.
Neuraminic acid
True or False:
Gangliosides are absent in nervous tissues
False:
Gangliosides are also present in nervous tissues in high concentration.
They function in cell-cell recognition and communication and as receptors for hormones and bacterial toxins such as cholera toxin.
Gangliosides or neuraminic acid ???
The simplest ganglioside found in tissues is _____, which contains ceramide, one molecule of NeuAc and one molecule of galactose.
GM3
_____, a more complex ganglioside derived from GM3, is of considerable biologic interest as it is known to be the receptor in human intestine for cholera toxin.
GM1
Other gangliosides can contain anywhere from one to five molecules of sialic acid, giving rise to _______________.
di-trisialogangliosides
All steroids have a similar cyclic nucleus resembling ______________ (rings A, B and C) to which a cyclopentane ring (D) is attached.
Phenanthrene
It is important to realize that in structural formulas of steroids, a simple hexagonal ring denotes a completely ____________ with all valences satisfied by hydrogen bonds unless shown otherwise; it is not a benzene ring.
Saturated six-carbon ring
If the compound has one or more hydroxyl groups and no carbonyl or carboxyl groups, it is a ________ and the name terminates in -ol.
Sterol
Each of the six-carbon rings of the steroid nucleus is capable of existing in the three-dimensional conformation either of a “______” or a “_________”.
Chair
Boat
In naturally occuring steroids, virtually all the rings are in the _______ form, which is the more stable conformation.
Chair
___________ is widely distributed in all cells of the body but particularly in nervous tissue.
Cholesterol
It is a major constituent of the plasma membrane and of plasma lipoprotein.
Cholesterol
Cholesterol is found as _____________, where the hydroxyl group on position 3 is esterified with a long-chain fatty acid.
Cholesteryl ester
_____________ is a precursor of Vitamin D.
Ergosterol
__________ occurs in plants and yeast and is important as a dietary source of Vitamin D.
Ergosterol
When irradiated with ultraviolet light in the skin, ring B is opened to form _______________ in a process similar to the one that forms _____________ from 7-dehydro-cholesterol in the skin.
Vitamin D2
Vitamin D3
Although not steroids, ____________ are related because they are synthesized, like cholesterol, from five-carbon isoprene units.
Polyprenoids
_____________ participates in the respiratory chain in mitochondria.
Ubiquinone
The long-chain alcohol ___________, which takes part in glycoprotein synthesis by transferring carbohydrate residues to aspargine residues of the polypeptide.
Dolichol
The deleterious effects are considered to be caused by _____________, molecules that have unpaired valence electrons, making them highly reactive.
Free radicals
Free radical containing oxygen are termed ________________.
Reactive oxygen species (ROS)
These are produced during peroxide formation from fatty acids containing methylene-interrupted double bonds, that is, those found in the naturally occuring polyunsaturated fatty acids.
ROS
______________ is a chain reaction providing a continuous supply of ROS that initiate further peroxidation and thus has potentially devastating effects.
Lipid peroxidation
The whole process can be depicted as follows:
- Initiation
- Propagation
- Termination
To control and reduce lipid peroxidation, both humans in their activities and nature invoke the use of ______________.
Antioxidants
Are antioxidants used as food additives:
- Propyl gallate
- Butylated hydroxyanisole (BHA)
- Butylated hydroxytoluene (BHT)
Naturally occuring antioxidants include Vitamin E (tocopherol), which is __________ and urate and Vitamin C which are _______.
Lipid soluble
Water soluble
Preventive antioxidants include catalase and other peroxidases such as ______________________ that react with ROOH.
Glutathione peroxidase
__________ which is an essential component of glutathione peroxidase and regulates its activity.
Selenium
DTPA
Diethylenetriaminepentaacetate
In vivo, the prinicipal-chain breaking antioxidants are _____________, which acts in the aqueous phase to trap superoxide free radicals urate and __________, which acts in the lipid phase to trap ROO radicals.
Superoxide dismutase
Vitamin E
Peroxidation is also catalyzed in vivo by heme compounds and by ______________ found in platelets and leukocytes.
Lipoxygenases
Other products of auto-oxidation or enzymic oxidation of physiologic significance include ______ (formed from cholesterol) and _______ (formed from the peroxodation of polyunsaturated fatty acids such as arachidonic acid).
Oxysterols
Isoprostanes
____________ may be formed by sonicating an ampiphatic lipid in an aqueous medium.
Liposomes
Aggregation of bile salts into micelles and liposomes and the formation of _____________ with the products of fat digestion are importamt in facilitating absorption of lipids from the intestine.
Mixed micelles
_____________ are of potential clinical use, particularly when combined with tissue-specific antibodies, as carriers of drugs in the circulation, targeted to specific organs for example in cancer therapy.
Liposomes
In addition, they are used for gene transfer into vesicular cells and as carriers for topical and transdermal delivery of drugs and cosmetics.
Liposomes
___________ are much larger particles, formed usually by nonpolar lipids in an aqueous medium.
Emulsions
