Test Bank for Lehninger Principles of
Biochemistry 5th Edition by Nelson
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Multiple Choice Questions
1. Structural lipids in membranes
Pages: 343-345 Difficulty: 2 Ans: A
Which of the following statements concerning fatty acids is correct?
1. One is the precursor of prostaglandins.
2. Phosphatidic acid is a common one.
3. They all contain one or more double bonds.
4. They are a constituent of sterols.
5. They are strongly hydrophilic.
2. Storage Lipids
Pages: 346-358 Difficulty: 2 Ans: E
Which of the following molecules or substances contain, or are derived from,
fatty acids?
1. Beeswax
2. Prostaglandins
3. Sphingolipids
4. Triacylglycerols
5. All of the above contain or are derived from fatty acids.
3. Storage Lipids
Pages: 349 Difficulty: 2 Ans: B
Biological waxes are all:
1. trimesters of glycerol and palmitic acid.
2. esters of single fatty acids with long-chain alcohols.
3. trimesters of glycerol and three long chain saturated fatty acids.
4.
5. none of the above.
4. Storage Lipids
Pages: 346-358 Difficulty: 2 Ans: B
Which of the following statements is true of lipids?
1. Many contain fatty acids in ester or amide linkage.
2. Most are simply polymers of isoprene.
3. Testosterone is an important sphingolipid found in myelin.
4. They are more soluble in water than in chloroform.
5. They play only passive roles as energy-storage molecules.
5. Structural lipids in membranes
Pages: 351-352 Difficulty: 2 Ans: D
Which of the following contains an ether-linked alkyl group?
1. Cerebrosides
2. Gangliosides
3. Phosphatidyl serine
4. Platelet-activating
Platelet-activating factor
5. Sphingomyelin
6. Structural lipids in membranes
Pages: 352-353 Difficulty: 2 Ans: A
Sphingosine is not a component of:
7. Structural lipids in membranes
Page: 352 Difficulty: 2 Ans: D
Which of the following statements about membrane lipids is true?
1. Glycerophospholipids
Glycerophospholipids are found only in the membranes of plant cells.
2. Glycerophospholipids
Glycerophospholipids contain fatty acids linked to glycerol through
amide bonds.
3. Lecithin (phosphatidylcholine),
(phosphatidylcholine), which is used as an emulsifier in
margarine and chocolate, is a sphingolipid.
4. Some sphingolipids include oligosaccharides in their structure.
5. Triacylglycerols
Triacylglycerols are the principal components of erythrocyte membranes.
8. Structural lipids in membranes
Page: 352 Difficulty: 2 Ans: A
Which of the following is true of sphingolipids?
1. Cerebrosides and gangliosides are sphingolipids.
2. Phosphatidylcholine
Phosphatidylcholine is a typical sphingolipid.
3. They always contain glycerol and fatty acids.
4. They contain two esterified fatty acids.
5. They may be charged, but are never amphipathic.
9. Structural lipids in membranes
membranes
Pages: 352-354 Difficulty: 2 Ans: B
A compound containing N-acetylneuraminic acid (sialic acid) is:
1.
2. ganglioside GM2.
3.
4. platelet-activating
platelet-activating factor.
5.
10. Lipids as signals, cofactors, and pigments
Pages: 352-363 Difficulty: 2 Ans: B Fatty
acids are a component of:
1.
2.
3.
4. vitamin D.
5. vitamin K.
11. Structural lipids in membranes
Pages: 355-356 Difficulty: 2 Ans: A
Which of the following statements about sterols is true?
1. All sterols share a fused-ring structure with four rings.
2. Sterols are found in the membranes of all living cells.
3. Sterols are soluble in water, but less so in organic solvents such as
chloroform.
4. Stigmasterol is the principal sterol in fungi.
5. The principal sterol of animal cells is ergosterol.
12. Structural lipids in membranes Pages:
355-356 Difficulty: 2 Ans: B Which of the
following is not true of sterols?
1. Cholesterol is a sterol that is commonly found in mammals.
2. They are commonly found in bacterial membranes.
3. They are more common in plasma membranes than in
intracellular membranes (mitochondria, lysosomes, etc.).
4. They are precursors of steroid hormones.
5. They have a structure that includes four fused rings.
13. Structural lipids in membranes
Page: 355 Difficulty: 2 Ans: A
Which of the following best describes the cholesterol molecule?
1. Amphipathic
2. Nonpolar, charged
charged
3. Nonpolar, uncharged
uncharged
4. Polar, charged
5. Polar, uncharged
14. Structural lipids in membranes
Page: 356 Difficulty: 2 Ans: A
Tay-Sachs disease is the result of a genetic defect in the metabolism of:
1.
2. phosphatidyl
phosphatidyl ethanolamine.
3.
4.
5. vitamin D.
15. Storage Lipids
Pages: 357-361 Difficulty: 2 Ans: C
An example of a glycerophospholipid
glycerophospholipid that is involved in cell signaling is:
1. arachidonic acid.
2.
3.
4.
5. vitamin A (retinol).
16. Lipids as signals, cofactors, and pigments
Pages: 358 Difficulty: 2 Ans: B
Non-steroidal anti-inflamm
anti-inflammatory
atory drugs (NSAIDS)
(NSAIDS) like aspirin
aspirin and ibuprofen
ibuprofen act
by blocking production
production of:
1. biological waxes
2. prostaglandins
3. sphingolipids
4. vitamin D
5. none of the above
17. Lipids as signals, cofactors, and pigments
Pages: 360-363 Difficulty: 1 Ans: B
Which of the following is not a fat-soluble vitamin?
1. A
2. C
3. D
4. E
5. K
18. Lipids as signals, cofactors, and pigments
Pages: 360-363 Difficulty: 2 Ans: C Which
vitamin is derived from cholesterol?
1. A
2. B12
3. D
4. E
5. K
19. Lipids as signals, cofactors, and pigments
Page: 361 Difficulty: 2 Ans: E
Identify the molecule(s) derived from sterols.
1. Arachidonic acid
2. Gangliosides
3. Phosphatidylglycerol
4. Prostaglandins
5. Vitamin D
Short Answer Questions
20. Storage lipids
Pages: 344-345 Difficulty: 1
Circle the fatty acid in each pair that has the higher melting temperature.
(a) 18:1D9 18:2D9,12
(b) 18:018:1D9
(c) 18:016:0
Ans: (a) 18:1D9 (b) 18:0 (c) 18:0
21. Storage lipids
Pages: 344-345 Difficulty: 2
Describe the dependence of the melting point of a fatty acid upon (a) chain length
and (b) unsaturation; (c) explain these dependencies in molecular terms.
Ans: All other things being equal, (a) the longer the acyl chain, the higher the
melting temperature; and (b) the more unsaturation, the lower the melting
temperature. (c) The melting temperature is a measure of the thermal energy needed
to break the intermolecular interactions that stabilize
s tabilize the “solid” form of a
lipid, which depends upon how well the individual lipid molecules fit into
the nearly
crystalline array of lipids. When a shorter acyl chain lies between two longer
chains
in a nearly crystalline array of lipid molecules, there is a cavity at the end of the
short acyl group that allows freer motion to the neighboring acyl chains. A cis
double bond introduces a “kink” into the acyl chain, so that it does not pack
as easily
with its straighter neighbors.
22. Storage lipids
Page: 345 Difficulty: 1
What is the effect of a double bond on fatty acid structure?
Ans: Most double bonds in fatty acids are in the cis configuration.
configuration. This results in a
rigid bend in the hydrocarbon chain. (See Fig. 10-1, p. 345.)
23. Storage lipids
Pages: 345-346 Difficulty: 2
In cells, fatty acids are stored as triacylglycerols for energy reserves. (a) What is
the
molecule to which fatty acids are esterified to form triacylglycerols?
triacylglycerols? (b) Define
the
logic behind cells storing fatty acids in esterified form.
Ans: (a) Three fatty acids are esterified to glycerol. (b) Triacylglycerols
Triacylglycerols are
uncharged and insoluble in water. They form lipid droplets within adipocytes,
which do not contribute to the osmolarity of the cytosol in those cells, and do
not require any water of hydration.
24. Storage lipids
Pages: 345-350 Difficulty: 2
What is the most significant chemical difference between triacylglycerols and
glycerophospholipids
glycerophospholipids that leads to their different functions?
Ans: Triacylglycerols are nonpolar hydrophobic molecules that can be stored
in specialized nonaqueous cellular compartments. Glycerophospholipids
Glycerophospholipids are
amphipathic molecules that can serve as structural components of
membranes, which have hydrophilic and hydrophobic regions.
re gions.
25. Storage lipids
Pages: 346-347 Difficulty: 2
Describe three functions of triacylglycerols in mammals
mammals and one function in
higher plants.
Ans: Triacylglycerols provide mammals with (1) stored fuel, (2) insulation, and (3) a
source of metabolic water. In some animals, such as camels and desert rats, the
oxidation of stored lipids provides water; in hibernating animals, oxidation
of stored
lipids generates heat to maintain body temperature (see Chapter 4). In plants,
oxidation of the triacylglycerols stored in seeds provides the energy and
precursors for
for biosynthetic
biosynthetic processes during
during germination,
germination, before photosynthetic
photosynthetic
mechanisms become functional.
26. Structural lipids in membranes
membranes
Page: 348 Difficulty: 2
What are the chemical components of a biological wax, and what is their
general structure?
Ans: A wax consists of a long-chain fatty acid in ester linkage with a long-chain
fatty
alcohol. (See Fig. 10-5, p. 348.)
27. Structural lipids in membranes
membranes
Page: 351 Difficulty: 2
Draw the structure of phosphatidylserine in the ionic form it would have at pH 7.
Ans: For this structure, see Fig. 10-8, p. 350. At neutral pH, there is a charge on
the
phosphate group,
group, and serine is in the zwitterionic
zwitterionic form; it has a protonated amino
amino
group and an ionized carboxyl group.
28. Structural lipids in membranes
membranes
Page: 351 Difficulty: 3
Give the structure of phosphatidylethanolamine
phosphatidylethanolamine containing one palmitate and one
oleate. Show the ionic form expected at pH 7. How many ester bonds are there in
this compound?
Ans: See Fig. 10-9, p. 351 for the phospholipid structure and Table 10-1, p. 344 for
the structures of the fatty acids. There are two carboxylate esters and two
phosphate esters
esters (one phosphodiester)
phosphodiester) in
in the molecule.
29. Structural lipids in membranes
Page: 351 Difficulty: 2
Draw the structure of phosphatidylcholine. Circle the part of the molecule that is
polar and draw an arrow
arrow to the part
part that is nonpolar.
nonpolar.
Ans: For this structure, see Fig. 10-9, p. 351. At neutral pH, there is a negative
charge on the phosphate group, and the quaternary amino group of choline carries
a
fixed positive charge; this entire phosphorylcholine
phosphorylcholine moiety is polar. The acyl
chains
attached to glycerol are the nonpolar part of the molecule.
30. Structural lipids in membranes
Page: 351 Difficulty: 2
Show the basic structure of all glycerophospholipids.
Ans: All glycerophospholipids
glycerophospholipids have two fatty acids in ester linkage with C-1 and
C-2
of glycerol; often the fatty acid at C-1 is saturated, and that at C-2 is unsaturated.
C-
3 of glycerol is joined to an alcohol-containing head group through
a phosphodiester
phosphodiester
linkage, which is negatively charged at neutral pH. (See Fig. 10-9, p. 351.)
31. Structural lipids in membranes
membranes
Page: 351 Difficulty: 3
What chemical features distinguish a plasmalogen from a common
glycerophospholipid?
Ans: (1) The long-chain acyl group attached to C-1 of glycerol is ether-linked in a
plasmalogen, but
but is an ester-linked
ester-linked fatty acyl
acyl group in typical glycerophospholipids.
glycerophospholipids.
(2) There is a double bond between C-1 and C-2 of this fatty acyl chain
in plasmalogens, but not in other phospholipids. (See Fig. 10-10, p. 351.)
32. Structural lipids in membranes
membranes
Page: 353 Difficulty: 2
Show the structure of sphingosine and indicate the relationship
between sphingosine
sphingosine and ceramide.
Ans: The structure of sphingosine is shown in Fig. 10 -13, p. 353, which also shows
that the attachment of a fatty acyl group to sphingosine in amide linkage converts
it to ceramide.
33. Structural lipids in membranes
membranes
Page: 353 Difficulty: 3
What chemical features distinguish a cerebroside from a ganglioside?
Ans: A cerebroside has a single sugar residue joined to ceramide; a ganglioside
has an oligosaccharide joined to ceramide. (See Fig. 10-13,
10 -13, p. 353.)
34. Lipids as signals, cofactors, and pigments
Pages: 353-361 Difficulty: 2
Match the compounds on the left with the important roles they play listed on the
right. (Answers are used only once.)
(a) prostaglandins ___ blood clotting
(b) sphingolipids ___ necessary for sight
(c) thromboxanes ___ mediates pain and inflammation
inflammation
(d) vitamin A ___ important component of myelin membranes
Ans: c; d; a; b
35. Lipids as signals, cofactors, and pigments
Pages: 355 Difficulty: 3
Describe the differences between the glycosphingolipids corresponding
corresponding to the A,
B and O human blood group antigens.
Ans: The type O structure is found in all three glycosphingolipids. In both type
A and
type B, there is an added sugar; this sugar differs between type A and B.
36. Structural lipids in membranes
Page: 356 Difficulty: 2
Explain the cause of hereditary diseases of sphingolipid metabolism, such as Tay-
Sachs and Niemann-Pick diseases.
Ans: These diseases are the result of mutations in the genes that code for enzymes
of sphingolipid breakdown. The mutant enzyme is defective and unable to
catalyze
its reaction in the metabolic pathway; this results in the accumulation of the
metabolic intermediate that is the substrate for the enzyme. (See Box 10-2, p. 356.)
37. Lipids as signals, cofactors, and pigments
Pages: 360-363 Difficulty: 2
Match each of these vitamins with its biological role: Vitamins A, D, E, K.
____ blood clotting
clotting
____ vision
____ Ca2+ and phosphate metabolism
metabolism
____ prevention of
of oxidative damage
damage
Ans: K; A; D; E
38. Lipids as signals, cofactors, and pigments
Pages: 359-361 Difficulty: 2
Show the structure of isoprene; explain what is meant by isoprenoid
compounds and give an example.
Ans: The structure is shown on page 361. Isoprenoid compounds
compounds contain chains
that consist of multiple isoprene units. (See Fig. 10-22, p. 362, for examples.)
39. Lipids as signals, cofactors, and pigments
Pages: 361-362 Difficulty: 2
What do all these compounds have in common: vitamin A, vitamin K,
ubiquinone, and dolichol?
Ans: They are all lipids with potent biological activities derived from isoprenoid
precursors.
40. Working with Lipids
Pages: 363-364 Difficulty: 2
Explain why extraction of lipids from tissues requires organic solvents.
Ans: Lipids are either strongly hydrophobic or amphipathic. Because the solvent
in
tissues is water, lipids are mainly present in aggregates. This aggregation does not
occur in organic solvents; as a result, the lipids are more soluble and thus
extractable from the tissues.
41. Working with Lipids
Pages: 364-365 Difficulty: 3
If beeswax, cholesterol, and phosphatidylglycerol were dissolved in chloroform,
then subjected to thin-layer chromatography on silica gel using a mixture of
chloroform/methanol/water as the developing solvent, which would move fastest?
Ans: In this chromatography,
chromatography, the least polar compound (beeswax) moves fastest
and the most polar (phosphatidylglycerol, which has a negative charge on its
head group) moves the slowest. (See Fig. 10-24, p. 364.)
