Biochemistry 4th edition voet test bank

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Chapter 9: Lipids and Biological Membranes Matching A) B) C) D) E) F) G) H) I) J) K) L) M)

amphiphiles vitamin D arachidonic acid phosphatidylethanolamine sterol gangliosides phosphatidylcholine glycerophospholipids sphingomyelins cholesterol triacylglycerols plasmalogen nonpolar

1. ______ are the lipids that are most abundant even though they are not components of membranes.

Ans: K Level of Difficulty: Easy Section: 9.1.B Learning objective: Lipid Classification

2. They ______ are a class of amphipathic molecules that comprise the major lipid components of the cell membrane.

Ans: H Level of Difficulty: Easy Section: 9.1.C Learning objective: Lipid Classification

3. The myelin sheath contains high levels of ______.

Ans: I Level of Difficulty: Easy Section: 9.1.D Learning objective: Lipid Classification

4. A steroid-derived hormone that must be activated by hydroxylation, ______ regulates Ca2+ metabolism.

Ans: B Level of Difficulty: Easy Section: 9.1.E Learning objective: Lipid Classification

5. A derivative of______ is the major lipid in lung surfactant.

Ans: G Level of Difficulty: Easy Section: 9.1.F Learning objective: Lipid Classification

6. Members of the ______ family have four fused, nonplanar rings and a C3-OH group.

Ans: E Level of Difficulty: Easy Section: 9.1.E Learning objective: Lipid Classification

7. A glycerophospholipid in which the C1 substituent linkage forms a vinyl ether that is more easily oxidized than its ester counterpart is called a ______.

Ans: L Level of Difficulty: Easy Section: 9.1.D Learning objective: Lipid Classification

8. Glycosphingolipids with complex carbohydrate head groups that often serve as cellular receptors are ______.

Ans: F Level of Difficulty: Easy Section: 9.1.D Learning objective: Lipid Classification

9. With respect to polarity, membrane lipids can be described as ______.

Ans: A Level of Difficulty: Easy Section: 9.1.A Learning objective: Lipid Classification

10. Eicosanoids are 20-carbon compounds derived from ______.

Ans: C Level of Difficulty: Easy Section: 9.1.F Learning objective: Lipid Classification

Multiple Choice 11. Which of the following statements are true regarding fatty acids?

I. Fatty acids with fewer than 14 carbons are the most common.

II. Synthesis of fatty acids occurs in 2 carbon units.

III. Fatty acids with conjugated double bonds are the most common type of fatty acid.

IV. In higher plants and animals, C16 and C18 species predominate.

A) I, II, III, IV B) I, II, III C) I, III D) II, III, IV E) II, IV Ans: E Level of Difficulty: Moderate Section: 9.1.A Learning objective: Lipid Classification

12. Rank the melting points of the following fatty acids from highest to lowest: (1) (2) (3) (4) (5)

cis-oleic(18:1) trans-oleic (18:1) linoleic (18:2) steraic (18:0) palmitic (16:0)

A) 1 > 2 > 3 B) 4 > 5 > 2 C) 4 > 5 > 3 D) 5 > 4 > 2 E) none of the above

> 5 > 1 > 2 > 1

> 4 > 3 > 1 > 3

Ans: B Level of Difficulty: Difficult Section: 9.1.A Learning objective: Lipid Classification

13. Which of the following lipid types is the least polar?

A) triacylglycerols B) glycerophospholipids C) sphingolipids D) gangliosides E) glycolipids Ans: A Level of Difficulty: Easy Section: 9.1.B-D Learning objective: Lipid Classification

14. Cholesterol A) incorporation into the membrane results in increased rigidity.

B) functions as a precursor to cerebrosides.

C) is synthesized in two-carbon units.

D) is synthesized from steroid hormones.

E) all of the above Ans: A Level of Difficulty: Moderate Section: 9.1.E and F Learning objective: Lipid Classification

15. A suspension of which of the following is most likely to form a liposome?

I. fatty acids II. triacylglycerols III. glycerophospholipids IV. sphingomyelins A) I, II B) II, III C) III, IV D) II, IV E) I, IV Ans: C Level of Difficulty: Moderate Section: 9.2.A Learning objective: Lipid Bilayers

16. Which of the following is true about membrane proteins embedded within the lipid bilayer?

A) An increased temperature of the bilayer decreases the rate of transverse diffusion of the membrane protein.

B) They undergo transverse diffusion approximately every 5 seconds at body temperature.

C) They undergo transverse diffusion readily at body temperature unless their movement is restricted by other cellular components.

D) As the temperature decreases, lateral diffusion of the membrane protein is restricted in bilayers with lipids which have longer chain fatty acids and fewer double bonds.

E) Lateral diffusion of the membrane protein occurs independent of bilayer composition and temperature.

Ans: D Level of Difficulty: Difficult Section: 9.2.B Learning objective: Lipid Bilayers

17. Which of the following statements describes integral membrane proteins?

I. They protect the contents of the cell from chaotropic agents such as urea.

II. They are easily dissociated from the membrane by changes in pH or high salt concentration.

III. They are held tightly in place by hydrophobic effects between the membrane and hydrophobic amino acids.

A) I, II, III B) I, III C) I D) II E) III Ans: E Level of Difficulty: Difficult Section: 9.3.A Learning objective: Membrane Proteins

18. Which experiment listed below did NOT verify the fluid mosaic model of membranes?

A) observation of lateral movement of membrane across the cell while anchored to a microscope slide.

B) monitoring the transverse diffusion of human proteins within a mouse cell membrane.

C) membrane fusion between mouse and human cells.

D) monitoring the lateral diffusion of fluorphores both bleached and unbleached.

E) All of the above describe experiments that verified the fluid mosaic model of membranes.

Ans: B Level of Difficulty: Difficult Section: 9.4.A, B Learning objective: Membrane Structure and Assembly 19. Which of the following proteins are synthesized on free ribosomes?

A) mitochondrial proteins B) secretory proteins C) signal peptides D) lysosomal proteins E) transmembrane proteins Ans: A Level of Difficulty: Moderate Section: 9.4.D Learning objective: Membrane Structure and Assembly

20. The protein that forms a transmembrane pore that allows growing polypeptides to pass through the RER membrane is called the ______.

A) signal recognition particle B) signal peptide C) docking protein D) translocon E) none of the above Ans: D Level of Difficulty: Easy Section: 9.4.D Learning objective: Membrane Structure and Assembly 21. Unsaturated fatty acids: A) are commonly found in plants and animals B) usually contain a double bond with cis stereochemistry C) sometimes contain multiple double bonds D) have lower melting points than the analogous saturated fatty acids E) all of the above Ans: E Level of Difficulty: Easy Section: 9.1.A Learning objective: Lipid Classification 22. Triglycerides contain more metabolic energy per unit weight than glycogen because: I. Glycogen has greater polarity than fatty acids.

II. Fatty acids predominate in an anhydrous form III. Fatty acids are less oxidized than carbohydrates.

IV. Triglycerides have a higher average molecular mass.

A) I, II, III, IV B) I, II, III C) I, II D) II, III E) III Ans: B Level of Difficulty: Moderate Section: 9.1.B Learning objective: Lipid Classification

23. Adipocytes A) are specialized cells for the synthesis of triglycerides.

B) are specialized cells for short term energy storage.

C) provide compartments for efficient membrane bilayer synthesis.

D) exist primarily in a thin layer surrounding major muscle groups as a rapid high energy source.

E) All of the above characterize adipocytes.

Ans: A Level of Difficulty: Easy Section: 9.1.B Learning objective: Lipid Classification

24. Sphingolipids I. contain a glycerol core with a phosphocholine headgroup.

II. contain a modified sphingosine.

III. often function as receptor components of membranes.

IV. function as a precursor to sterols.

A) I, II, IV B) II, IV C) I, II, III D) II, III E) II, III, IV Ans: D Level of Difficulty: Moderate Section: 9.1.D Learning objective: Lipid Classification

25. While fatty acids are most often formed by the condensation of __-carbon units, isoprenoids are assembled from __-carbon units.

A) 5, 3 B) 4, 2 C) 2, 3 D) 2, 5 E) 3, 4 Ans: D Level of Difficulty: Easy

Section: 9.1.F Learning objective: Lipid Classification 26. Which of the following is comprised primarily of fatty acids and other single tailed amphiphiles?

A) lipid bilayers B) two-dimensional membranes C) liposomes D) micelles E) solvent-filled vesicles Ans: D Level of Difficulty: Easy Section: 9.2.A Learning objective: Lipid Bilayers

27. Cold blooded animals modulate the fatty acid composition of their membranes as a function of temperature in order to A) adjust the membrane thickness and increase thermal insulation.

B) maximize available fatty acids for metabolic use.

C) ensure consistent membrane fluidity.

D) compensate for decreasing cholesterol solubility.

E) all of the above Ans: C Level of Difficulty: Easy Section: 9.2.B Learning objective: Lipid Bilayers

28. Which of the following amino acids from an integral membrane protein would likely contact the membrane?

A) Asn B) Gln C) Glu D) Ala E) Asp Ans: D Level of Difficulty: Easy Section: 9.3.A Learning objective: Membrane Proteins

29. Transmembrane proteins I. are predominantly constructed of a single hydrophobic α-helix.

II. are often constructed from bundles of hydrophobic -helices.

III. are sometimes constructed from β-barrels with hydrophobic interiors and exteriors.

IV. may have transmembrane helices identified by the free energy of transfer to water.

A) I, III, IV B) II, III C) II, III, IV D) I, IV E) II, IV Ans: C Level of Difficulty: Moderate Section: 9.3.A Learning objective: Membrane Proteins 30. Which of the following is (are) NOT found as covalently attached anchors in lipid-linked proteins?

A) isoprenoid groups B) fatty acids C) cholesterol and other sterols D) glycosylphosphatidyl inositol groups E) All of the above are found as covalently attached anchors in lipid-linked proteins.

Ans: C Level of Difficulty: Easy Section: 9.3.B Learning objective: Membrane Proteins 31. Which of the following classes of proteins associates with the membrane bilayer with the lowest energy and would therefore be most difficult to separate from the membrane?

A) extrinsic proteins B) lipid-linked proteins C) transmembrane proteins D) peripheral proteins E) hydrophilic proteins Ans: C Level of Difficulty: Difficult

Section: 9.3.A Learning objective: Membrane Proteins 32. The biconcave shape of erythrocytes which maximizes rapid diffusion of oxygen is primarily maintained by A) the covalent attachment of organelles within the cell to the membrane.

B) high levels of rigid cholesterol and saturated lipids that strengthen the membrane.

C) a network of embedded spectrin that crosslink to other membrane proteins, D) a network of tightly-packed anion channel proteins.

E) a relatively low concentration of integral membrane proteins allowing tighter packing of lipid molecules within the membrane.

Ans: C Level of Difficulty: Moderate Section: 9.4.B Learning objective: Membrane Structure and Assembly

33. The _________ model describes the cell membrane as an assortment of integral proteins suspended freely in a lipid bilayer.

A) FRAP B) cellular fusion C) transverse diffusion D) lateral diffusion E) fluid mosaic Ans: E Level of Difficulty: Easy Section: 9.4.A Learning objective: Membrane Structure and Assembly 34. N-terminal signal peptides function to direct proteins A) destined for secretion.

B) to the endoplasmic reticulum.

C) destined to be part of the lysosomes.

D) all of the above E) none of the above Ans: D Level of Difficulty: Easy Section: 9.4.D Learning objective: Membrane Structure and Assembly

35. The _________, which is found embedded in the endoplasmic reticulum, is a _______ protein.

A) SRP receptor…signal B) ribosome…transmembrane pore C) translocon…transmembrane pore D) translocon…peripheral E) ribosome…signal Ans: C Level of Difficulty: Moderate Section: 9.4.D Learning objective: Membrane Structure and Assembly

36. In bacteria, phospholipids are synthesized: A) on the cytoplasmic face of cell membranes B) at the rough endoplasmic reticulum C) on the extracellular face of the cell membrane D) on site at the endoplasmic reticulum.

E) nonenzymatically at the site of the membrane.

Ans: A Level of Difficulty: Moderate Section: 9.4.C Learning objective: Membrane Structure and Assembly

37. Which of the following segments of the integral membrane protein glycophorin most likely contains the membrane-spanning sequence?

A) LSTTEVAMHTTTSSSVSKSY B) SQTNDTHKRDTYAATPRA C) VSEISVRTVYPPEEETGE D) ITLIIFGVMAGVIGTILLI E) YGIRRLIKKSPSDVKPLP Ans: D Level of Difficulty: Moderate Section: 9.3.A Learning objective: Membrane Proteins

38. Which would be most likely to be found in the membranes of mouse brain cells?

A) cholesterol B) glycerolphospholipids C) GM1, GM2, or GM3 D) all of the above E) none of the above Ans: D Level of Difficulty: Easy Section: 9.1.A, B, C, D, E Learning objective: Lipid Classification

39. The signal peptide sequence I. is often used to direct proteins to the lysosome for incorporation into the lysosome.

II. is usually not used for small eukaryotic proteins.

III. of some transmembrane proteins is embedded into the membrane as an anchor.

IV. is usually cleaved off the completed protein.

A) I, IV B) I, II, IV C) II, III, IV D) I, III, IV E) I, II, III, IV Ans: D Level of Difficulty: Moderate Section: 9.4.D Learning objective: Membrane Structure and Assembly

40. Glycosphingolipids with several attached carbohydrates (including at least one sialic acid) are called: A) plasmalogens B) ceramides C) sphingiosides D) gangliosides E) cerebrosides Ans: D

Level of Difficulty: Easy Section: 9.1.C Learning objective: Lipid Classification 41. Considering the characteristics of common fatty acids found in animals described in the text, which of the structures shown below would you consider the most rare fatty acid if found in animals?

A) Structure A B) Structure B C) Structure C D) Structure D E) All structures would be equally rare.

Ans: C Level of Difficulty: Moderate Section: 9.1.A Learning objective: Lipid Classification

42. Which of the structures below is an example of an -3 polyunsaturated fatty acid?

A) Structure A B) Structure B C) Structure C D) Structure D E) None of the above Ans: B Level of Difficulty: Moderate Section: 9.1.A Learning objective: Lipid Classification

43. Which of the following statements describes one reason that plant oils are generally healthier for human consumption than animal fats?

A) Plant oils usually contain more unsaturated fatty acids than animal fats.

B) Plant oils usually contain more trans fatty acids than animal fats.

C) Plant oils usually have a higher degree of saturation than animal fats.

D) Plant oils are glycerol based rather than phospholipid based.

E) Plant oils have shorter chain fatty acids than animal fats.

Ans: A Level of Difficulty: Moderate Section: 9.1.A and 9.1B Learning objective: Lipid Classification 44. Lung surfactants function to decrease the likelihood of collapse of the alveoli when air is expired. Based on your knowledge of lipids and amphipathic molecules, which of the following explains the mechanism by which the dipalmitoyl phosphatidylcholine (DPPC) can accomplish this task?

A) The hydrophilic head groups are bulky and expand the surface area of the alveoli.

B) The inclusion of saturated fatty acids on the glycerophospholipid allows close packing of tail groups which are fully extended and prevent collapse upon expiration.

C) The hydrophobic portion of the DPPC repel air, forcing the alveoli space open.

D) The choline portion of the molecule is bulky, thus increasing surface area of alveoli.

E) None of the above explain the mechanism.

Ans: B Level of Difficulty: Difficult Section: 9.1A and C Learning objective: Lipid Classification

45. Which of the following structures correctly represents a glycerophospholipid?

A) Structure A B) Structure B C) Structure C D) Structure D E) None of the above

Ans: A Level of Difficulty: Moderate Section: 9.1C Learning objective: Lipid Classification

46. Which of the following points to the correct location of attachment for a fatty acid which

would yield a ceramide?

A) Location A B) Location B C) Location C D) Location B or C E) The correct location is not shown Ans: A Level of Difficulty: Moderate Section: 9.1D Learning objective: Lipid Classification 47. Identify the compound below:

A) a glycerolphospholipid B) sphingosine C) ceramide D) spingomylelin E) ganglioside Ans: D Level of Difficulty: Moderate Section: 9.1D Learning objective: Lipid Classification

48. Use the diagram below to answer the following question. The enzyme flipase would catalyze which of the following types of reactions?

A) Exchange of a phospholipid in position A for a cholesterol in position A. B) Exchange for a lipid in position A for a lipid in position B. C) Exchange for a phospholipid in position A with a phospholipid in position C. D) Exchange for a lipid in position B for a lipid in position D. E) Exchange for a glycerolphospholipid in position A for a spingolipid in position C. Ans: B Level of Difficulty: Moderate Section: 9.4C Learning objective: Membrane Structure and Assembly 49. Which of the following correctly ranks the steps in the secretory pathway?

1. Synthesis occurs with a leading signal peptide 2. The SRP-ribosome complex binds the SRP receptor-translocon complex 3. The signal peptide binds the SRP and GDP is replaced with GTP 4. GTP hydrolysis results in dissociation of SRP and SR 5. SRP changes in conformation arresting peptide growth 6. The nascent protein begins to fold and post-translational modification is initiated 7. Signal peptidase cleaves the protein from the signal peptide A) 1, 2, 5, 4, 6, 7, 3 B) 1, 3, 5, 2, 4, 7, 6 C) 2, 4, 1, 3, 5, 6, 7 D) 2, 4, 3, 5, 4, 6, 7 E) 1, 3, 4, 2, 5, 7, 6 Ans: B Level of Difficulty: Difficult Section: 9.4D Learning objective: Membrane Structure and Assembly

50. Which of the following correctly describes the usefulness of SNAREs? I. They are essential for proper post-translation processing.

II. They are a critical element in the function of the secretory pathway.

III. They are effective at overcoming electrostatic repulsion between vesicle membranes.

IV. They facilitate anchoring between vesicle membranes.

A) I, II, III, IV B) II, III C) III D) IV E) III, IV Ans: E Level of Difficulty: Moderate Section: 9.4F Learning objective: Membrane Structure and Assembly 51. A researcher is developing a new drug for the treatment of influenza. Based on the information presented in the text about the influenza virus, which of the following drug reactions describes the action of this new drug?

A) A drug which specifically interrupts the conformational change that results from the pH change in the endosome.

B) A drug which enhances the function of a normally quiescent enzyme responsible for cleavage of the carbohydrate component on glycophorin A proteins.

C) A drug which readily binds the hemagglutinin tag and results in conformational change.

D) All of the above are potential actions of this new drug.

E) None of the above is a plausible reaction for this new drug.

Ans: D Level of Difficulty: Difficult Section: 9.4F Learning objective: Membrane Structure and Assembly

52. I-cell disease results in psychomotor retardation, skeletal deformities and death. Which of the following is true regarding this disease?

A) The disease results in inclusion of glycosaminoglycans and glycolipids due the absence of an essential carbohydrate marker that directs the lysosomal hydrolases to the lysosome.

B) The disease results in inclusion of glycolipids due mutations in the lysosomal hydrolases that render them inactive.

C) The disease results in increased expression of SNARE proteins that result in vesicle fusion and exchange of glycosaminoglycans.

D) The disease results from the lack of KDEL sequences which would normally signal their return to the ER following Golgi processing.

E) All of the above are true.

Ans: A Level of Difficulty: Difficult Section: 9.4D Learning objective: Membrane Structure and Assembly 53. Botox is used cosmetically to reduce wrinkles for a limited time interval. The function of Botox is described by which of the following?

A) Botox inhibits function of the hemagglutinin tag.

B) Botox relaxes small muscles by cleaving the leader peptide prior protein folding.

C) Botox functions by inhibiting function of the SNARE protein.

D) Botox functions by inhibiting the lysosomal protease cathepsin D. E) None of the above describes the function of Botox.

Ans: C Level of Difficulty: Moderate Section: 9.4D, E, and F Learning objective: Membrane Structure and Assembly

54. Coated vesicles are used to ensure that the enclosed protein maintains its proper orientation.

Clathrin is one type of protein used to coat vesicles. Which of the following is true regarding clathrin vesicles?

A) They transport proteins between successive components of the Golgi compartments.

B) They transport transmembrane proteins and GPI-linked proteins from the Golgi to the plasma membrane.

C) They transport proteins from the ER to the Golgi.

D) They form a rigid complex capable of protecting protein structure and orientation as it is passed from hydrophobic to hydrophilic environments.

E) None of the above.

Ans: B Level of Difficulty: Easy Section: 9.4E Learning objective: Membrane Structure and Assembly 55. Proteins which are passed from one Golgi compartment to the next in a successive fashion do so via a mechanism called____.

A) maturation B) cisternal progression C) retrograde transport D) anterograde transport E) medialgrade transport Ans: D Level of Difficulty: Easy Section: 9.4E Learning objective: Membrane Structure and Assembly 56. A researcher has designed a new drug that will block the release of certain neurotransmitters from the synaptic cleft. Which of the following reactions must be blocked by this new drug?

A) The drug binds the receptors in the postsynaptic membrane and blocks neurotransmitter binding.

B) The drug binds the presynaptic membrane greatly facilitating the rate of transverse diffusion, thus changing the composition of the membrane.

C) The drug enhances activity of SNARE proteins, thus facilitating fusion.

D) All of the above are plausible actions of this new drug.

E) None of the above is a plausible action of this new drug.

Ans: B Level of Difficulty: Difficult Section: 9.4F Learning objective: Membrane Structure and Assembly

57. Receptor-mediated endocytosis: A) is comparable to the activities of vesicle fusion.

B) superficially resembles binding of a clathrin coated vesicle to the plasma membrane.

C) superficially resembles the reverse of vesicle fusion to the plasma membrane.

D) mimics the function of the Golgi apparatus.

E) functions much like the SNARE mediated fusion process.

Ans: C Level of Difficulty: Easy Section: 9.4E and F Learning objective: Membrane Structure and Assembly 58. Which of the following processes presented in this chapter is (are) readily reversible with the help of enzymes known as thioesterases?

A) myristoylation B) glycosylphosphotidylinositalation C) palmitoylation D) all of the above E) none of the above Ans: C Level of Difficulty: Moderate Section: 9.3B Learning objective: Membrane Proteins 59. Which of the following lipids would NOT likely be found in a lipid raft?

I. glycosphingolipids II. glycerophospholipids III. cholesterol IV. palmitoleic acid A) I, IV B) I, II, IV C) II, IV D) III, IV E) IV Ans: C Level of Difficulty: Easy Section: 9.1A, D, E, 9.4C Learning objective: Lipid Classification and Membrane Structure and Assembly

60. Lipid bilayers with high concentrations of gangliosides are rare. Which of the following explanations is correct?

A) The hydrophobic tails on gangliosides form a conical shape rather than a cylindrical shape making close packing difficult.

B) Gangliosides contain large headgroups making close packing difficult.

C) Gangliosides contain trans fatty acids resulting in a bent hydrophobic tail making close packing difficult.

D) All of the above are correct.

E) None of the above is correct.

Ans: B Level of Difficulty: Moderate Section: 9.1D Learning objective: Lipid Classification