CHAPTER 10 LIPIDS 44 terms by nguyenl8

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which of the following statementsconcerning fatty acids is correct?

One is the precursor of prostaglandins

Which of the following molecules orsubstances contain, or are derivedfrom, fatty acids?

beeswaxprostaglandinssphingolipidstriacylglycerolsALL OF THE ABOVE CONTAIN OR ORDERIVED FROM FATTY ACID

Which of the following statements istrue of lipids?

Most are simply polymers of isoprene.

Which of the following contains anether-linked alkyl group?

Platelet-activating factor

Sphingosine is not a component of: cardiolipin

Which of the following statementsabout membrane lipids is true?

Some sphingolipids includeoligosaccharides in their structure.

Which of the following is true ofsphingolipids?

Cerebrosides and gangliosides aresphingolipids.

A compound containing N-acetylneuraminic acid (sialic acid) is:

ganglioside GM2

Fatty acids are a component of: cerebrosides

Which of the following statementsabout sterols is true?

All sterols share a fused-ring structurewith four rings

Which of the following is not true ofsterols?

They are commonly found in bacterialmembranes.

Which of the following best describesthe cholesterol molecule?

Amphipathic

Tay-Sachs disease is the result of agenetic defect in the metabolism of:

gangliosides

An example of a glycerophospholipidthat is involved in cell signaling is :

phosphatidylinositol

Which of the following is not a fat-soluble vitamin?

C

Which vitamin is derived fromcholesterol?

D

Identify the molecule(s) derived fromsterols.

Vitamin D

Circle the fatty acid in each pair thathas the higher melting temperature.

18:1^918:018:0

Describe the dependence of themelting point of a fatty acid upon (a)chain length and (b) unsaturation; (c)explain these dependencies inmolecular terms.

All other things being equal,(a) the longer the acyl chain, the higherthe melting temperature; and(b) the more unsaturation, the lowerthe melting temperature.(c) The melting temperature is ameasure of the thermal energy neededto break the intermolecular interactionsthat stabilize the "solid" form of a lipid,which depends upon how well theindividual lipid molecules fit into thenearly crystalline array of lipids. When ashorter acyl chain lies between twolonger chains in a nearly crystallinearray of lipid molecules, there is a cavityat the end of the short acyl group thatallows freer motion to the neighboringacyl chains. A cis double bondintroduces a "kink" into the acyl chain,so that it does not pack as easily withits straighter neighbors.

What is the effect of a double bond ona fatty acid structure?

Most double bonds in fatty acids are inthe cis configuration. This results in arigid bend in the hydrocarbon chain.

In cells, fatty acids are stored astriacylglycerols for energy reserves. (a)What is the molecule to which fattyacids are esterified to formtriacylglycerols? (b) Define the logicbehind cells storing fatty acids inesterified form.

(a) Three fatty acids are esterified toglycerol.(b) Triacylglycerols are uncharged andinsoluble in water. They form lipiddroplets within adipocytes, which do nocontribute to the osmolarity of thecytosol in those cells, and do notrequire any water of hydration.

What is the most significant chemicaldifference between triacylglycerols andglycerophospholipids that leads to theirdifferent functions?

Triacylglycerols are nonpolarhydrophobic molecules that can bestored in specialized nonaqueouscellular compartments.Glycerophospholipids are amphipathicmolecules that can serve as structuralcomponents of membranes, whichhave hydrophilic and hydrophobicregions.

Describe the three functions oftriacylglycerols in mammals and onefunction in higher plants.

Triacylglycerols provide mammals with(1) stored fuel, (2) insulation, and (3) asource of metabolic water. In someanimals, such as camels and desertrats, the oxidation of stored lipidsprovides water; in hibernating animals,oxidation of stored lipids generatesheat to maintain body temperature. Inplants, oxidation of triacylglycerolsstored in seeds provides the energyand precursors for biosyntheticprocesses during germination, beforephotosynthetic mechanisms becomefunctional.

What are the chemical components of abiological wax, and what is their generalstructure?

A wax consists of a long-chain fatty acidin ester linkage with a long-chain fattyalcohol.

What chemical features distinguish acerebroside from a ganglioside?

A cerebroside has a single sugarresidue joined to ceramide; aganglioside has an oligosaccharidjoined to ceramide.

prostaglandins mediates pain and inflammation

sphingolipids important component of myelinmembranes

thromboxanes blood clotting

vitamin A necessary for sight

Explain the cause of hereditarydiseases of sphingolipid metabolism,such as Tay-Sachs and Niemann-Pickdiseases.

These diseases are the result ofmutations in the genes that code forenzymes of sphingolipid breakdown.The mutant enzyme is defective andunable to catalyze its reaction in themetabolic pathway this results in theaccumulation of the metabolicintermediate that is the substrate forthe enzyme.

Vitamin K blood clotting

Vitamin A vision

Vitamin D Ca2+ and phosphate metabolism

Vitamin E prevention of oxidative damage

Show the structure of isoprenoid;explalin what is meant by isoprenoidcompounds and give an example.

Isoprenoid compounds contain chainsthat consist of multiple isoprene units.

What do all these compounds have incommon: vitamin A, vitamin K,ubiquinone, and dolichol?

They are all lipids with potent biologicalactivities derived from isoprenoidprecursors.

Explain why extraction of lipids fromtissues required organic solvents.

Lipids are either strongly hydrophobicor amphipathic. Because the solvent intissues is water, lipids are mainlypresent in aggregates. This aggregationdoes not occur in organic solvents; as aresult, the lipids are more soluble andthus extractable from the tissues.

If beeswax, cholesterol, andphosphatidylglycerol were dissolved inchloroform, then subjected to thin-layerchromatography on silica gel using amixture of chloroform/methanol/wateras the developing solvent, which wouldmove fastest?

In this chromatography, the least polarcompound (beeswax) moves fastestand the most polar(phosphatidylglycerol, which has anegative charge on its head group)moves the slowest.

Draw the structure ofphosphatidylserine in the ionic form itwould have at pH 7.

At neutral pH, there is a charge on thephosphate group, and serine is in thezwitterionic form; it has a protonatedamino group and an ionized carboxylgroup.

Give the structure ofphosphatidylethanolamine containingone palmitate and one oleate. Shwo theionic form expected at pH7. How manyester bonds are there in thiscompound?

There are two carboxylate esters andtwo phosphate esters (onephosphodiester) in the molecule.

Draw the structure ofphosphatidylcholine. Circle the part ofthe molecule that is polar and draw anarrow to the part that is nonpolar.

At neutral pH, there is a negativecharge on the phosphate group, andthe quaternary amino group of cholinecarries a fixed positive charge; thisentire phosphorylcholine moiety ispolar. The acyl chains attached toglycerol are the nonpolar part of themolecule.

Show the basic structure of allglycerophospholipids.

All glycerophospholipids have two fattyacids in ester linkage with C-1 and C-2of glycerol; often the fatty acid at C-1 issaturated, and that at C-2 is unsatured.C-3 of glycerol is jointed to an alcohol-containing head group through aphosphodiester linkage, which isnegatively charged at neutral pH.

What chemical features distinguish aplasmalogen from a commonglycerophospholipid?

(1) The long-chain acyl group attachedto C-1 of glycerol is ether-linked in aplasmalogen, but is an ester-linked fattyacyl group in typicalglycerophospholipids. (2) There is adouble bond between C-1 and C-2 ofthis fatty acyl chain in plasmalogens,but not in other phospholipids.

Show the structure of sphingosine andindicate the relationship betweensphingosine and ceramide.

The structure of sphingosine alsoshows that the attachment of a fattyacyl group to sphingosine in amidelinkage converts it to ceramide.