biochem chpt #9
45) Lipid-anchored membrane proteins that link to an isoprenoid chain via the sulfur atom of cysteine are called ________ proteins. A) prenylated B) sulfide-linked C) cysteine-anchored D) prostaglandins
: A Page Ref: Section 9-10
49) Why should it not be surprising that for many cells water requires a protein for its transport across a membrane? A) Water is very polar which inhibits its free diffusion across the membrane. B) All molecules require transport proteins to cross a membrane. C) The transport protein is needed to prevent the hydrolysis of the phospholipid chains as water crosses the membrane. D) There is never a concentration gradient for water across the membrane to drive its transport.
: A Page Ref: Section 9-11
50) In the mitochondria phosphate ion (PO43-) and H+ are transported together from the intermembrane space into the matrix. Which statement applies? A) The transport protein is a symport. B) The transport protein must have a relatively large central channel to accommodate both ions. C) The interior of the transport protein must be uncharged. D) All of the above.
: A Page Ref: Section 9-11
55) Valinomycin is an antibiotic that kills bacteria by surrounding K+ ions and shuttling them down their concentration gradient and across membranes. Which might be a cause of cell death? A) Disruption of secondary transport processes that depend on the K+ concentration gradient. B) Change in the pH of the bacterial cytosol. C) Blocking of bacterial pores with K+ ions. D) Massive denaturation of bacterial proteins upon change of the K+ concentration.
: A Page Ref: Section 9-11
60) Which statement is not true about G proteins? A) They are integral membrane proteins. B) They are multisubunit proteins consisting of α, β and γ subunits. C) They are slowly inactivated by their own GTPase activity. D) They act as transducers for hormones.
: A Page Ref: Section 9-12
62) The toxins from cholera and whooping cough both interfere with the proper functioning of ________. A) G proteins B) DNA polymerase C) ATP synthesis D) protein kinase A
: A Page Ref: Section 9-12
63) Which is not involved in signal transduction? A) Glycolytic pathway. B) Receptor tyrosine kinases. C) Adenylyl cyclase pathway. D) Inositol-phospholipid pathway.
: A Page Ref: Section 9-12
5) Which statement is true about the usual concentration of free fatty acids in cells? A) The concentration is low because it could disrupt cell membranes. B) The concentration is low because fatty acids are synthesized in the extracellular fluid. C) The concentration is high because of the demand for fatty acids in cell membranes. D) The concentration is high because the mitochondria are continuously synthesizing them.
: A Page Ref: Section 9-2
20) Which type of sphingolipid can also be classified as a phospholipid? A) Sphingomyelins. B) Cerebrosides. C) Gangliosides. D) Neurosides.
: A Page Ref: Section 9-5
29) Mitochondria differ from other cellular structures such as lysozomes or nuclei by having ________. A) a double membrane B) lipid-anchored membrane proteins C) a high level of cholesterol in the membrane D) allowing the free passage of free fatty acids across the membrane
: A Page Ref: Section 9-8
33) Which would you expect for the fatty acyl chains of the membrane phospholipids of bacteria grown at low temperature? A) Proportion of unsaturated fatty acyl groups increases. B) Proportion of unsaturated fatty acyl groups decreases. C) No change in the proportion of saturated versus unsaturated acyl groups. D) More cholesterol is produced and is inserted between the fatty acyl chains of the membrane.
: A Page Ref: Section 9-9
40) Determination of the tertiary structure of a membrane protein finds that the outer surface is composed primarily of hydrophobic residues. Which conclusion is most likely from this observation? A) It is a lipid-anchored membrane protein. B) It is an integral protein. C) The protein must be involved in passive transport. D) The protein can undergo transverse diffusion.
: B Page Ref: Section 9-10
41) Membrane passive transport and transport by channels and pores requires ________. A) energy input B) a protein carrier C) hexanoic acid D) ion gradients
: B Page Ref: Section 9-10
43) Which type of membrane protein might be dissociated from the membrane by changing the pH or the ionic strength? A) Integral membrane protein. B) Peripheral membrane protein. C) Lipid-anchored membrane protein. D) All of the above.
: B Page Ref: Section 9-10 / 44) You have purified a cell membrane and wish to isolate a transport protein from it. Which treatment might you select? A) Add a detergent. B) Change the ionic strength. C) React with a protease. D) Add phenylisothiocyanate (PITC). Answer: A Page Ref: Section 9-10
52) If the concentration of a solute is the same both inside and outside the cell, what might you expect with regard to its transport by a membrane protein? A) Since there is no concentration gradient, no transport either in or out of the cell is possible. B) Movement of the solute across the membrane could occur and cause accumulation on one side of the membrane by an active transport protein. C) The transport protein has been saturated. D) The solute must be phosphorylated with a phosphate group from ATP before further transport can occur.
: B Page Ref: Section 9-11
54) Which can serve as an energy source for secondary active transport? A) Light. B) Ion concentration gradient. C) Electron transport. D) ATP → ADP.
: B Page Ref: Section 9-11
56) The membrane transport protein Na+-K+ ATPase carries both Na+ and K+ ions across the plasma membrane. Typically the concentration of K+ inside cells is about 30 times higher inside the cell than outside. The concentration of Na+ is about 20 times less inside the cell than outside. Based on this information, which statement below is false? A) The proper functioning of Na+-K+ ATPase could serve as an energy source for secondary active transport proteins. B) It is a symport. C) Transport of Na+ and K+ must be coupled to an exergonic reaction. D) Na+-K+ ATPase likely undergoes conformational changes during transport.
: B Page Ref: Section 9-11
15) Triacylglycerols are not found in cell membranes because they are A) amphipathic. B) not amphipathic. C) not abundant in cells. D) charged at biological pH.
: B Page Ref: Section 9-3
18) Glycerophospholipids have ________ heads and long ________ fatty acid tails. A) polar; polar B) polar; hydrophobic C) hydrophobic; polar D) hydrophobic; hydrophobic
: B Page Ref: Section 9-4
24) Sterols are steroids which have A) a hydroxyl group at position C-17. B) a hydroxyl group at position C-3. C) the ability to accumulate as plaques in blood vessels. D) 5 fused rings instead of 4 fused rings. E) hydroxyl groups at both position C-3 and C-17.
: B Page Ref: Section 9-6
26) Which is not a function of cholesterol in mammals? A) Precursor of bile salts. B) Transport of Ca2+ across membranes. C) Modulate the fluidity of membranes. D) Precursor of steroid hormones.
: B Page Ref: Section 9-6
27) Eicosanoids participate in a variety of physiological responses and are derived from A) waxes. B) arachidonic acid. C) cholesterol. D) isoprene.
: B Page Ref: Section 9-7
28) Triacylglycerols cannot form lipid bilayers because they A) have hydrophobic tails. B) do not have polar heads. C) cannot associate with cholesterol. D) have polar heads. E) cannot engage in hydrophobic interactions.
: B Page Ref: Section 9-8
32) A sea creature richer in ________ can more likely live or migrate to an area of low temperature. A) arachidonic acid B) unsaturated fatty acids C) saturated fatty acids D) eicosanoids E) All of the above
: B Page Ref: Section 9-9
38) Regions on cell membranes called lipid rafts form because A) membrane proteins form them. B) cholesterol preferentially associates with sphingolipids. C) certain membrane protein patches aggregate. D) cholesterol and proteins bind to form them.
: B Page Ref: Section 9-9
47) Facilitated diffusion (passive transport) through a biological membrane is A) generally irreversible. B) driven by the ATP to ADP conversion. C) driven by a concentration gradient. D) endergonic.
: C Page Ref: Section 9-11
48) Which does not apply to the diffusion of O2, CO2 and small hydrophobic molecules across a membrane? A) Diffusion is driven by the concentration gradient across the membrane. B) The diffusion is spontaneous and there is a decrease in free energy as diffusion occurs. C) The transport is saturable. D) Membrane proteins are not needed for the diffusion process.
: C Page Ref: Section 9-11
53) Which is not a similarity between active transport proteins and enzymes? A) Both undergo conformational changes upon binding a substrate. B) Both are susceptible to inhibition. C) Both cause chemical modification to the substrate. D) Both can reach a saturation limit.
: C Page Ref: Section 9-11
58) In signal transduction what is an effector enzyme? A) An integral membrane protein that changes conformation upon binding of a ligand to a cell surface receptor. B) A small molecule that diffuses within a cell and carries a signal to its ultimate destination. C) A protein bound on the interior of a cell membrane that generates a second messenger. D) Protein bound on the exterior surface of a cell and is the receptor site for a ligand.
: C Page Ref: Section 9-12
61) In the adenyl cyclase signaling pathway the second messenger(s) is(are) ________. A) ATP and GTP B) protein kinase A C) cyclic AMP or cyclic GMP D) AMP
: C Page Ref: Section 9-12
4) A fatty acid designated as 20:0 is ________, while one that is designated 20:3 D5,8,11 is ________. A) simple; complex B) complex; simple C) saturated; unsaturated D) unsaturated; saturated E) monounsaturated; polyunsaturated
: C Page Ref: Section 9-2
6) Which statement is true about the most common naturally occurring fatty acids? A) They have 50-100 carbon atoms and an even number of carbon atoms. B) They have 50-100 carbon atoms and an odd number of carbon atoms. C) They have 12-20 carbon atoms and an even number of carbon atoms. D) They have 12-20 carbon atoms and an odd number of carbon atoms.
: C Page Ref: Section 9-2
7) A fatty acid designated w-3 A) has three double bonds. B) is saturated. C) has a double bond three carbons from the end of the chain. D) has a double bond three carbons from the a-carbon.
: C Page Ref: Section 9-2
9) Plasma levels of cholesterol and triglycerides are elevated by A) sphingolipids B) cis-fatty acids. C) trans-fatty acids. D) plant oils.
: C Page Ref: Section 9-2
14) Triglycerols containing only saturated long chain fatty acids tend to remain ________ at room temperature. A) unsaturated B) liquid C) solid D) oils
: C Page Ref: Section 9-3
19) Like plasmologens, sphingolipids are found in relative abundance in A) bacteria. B) plant cells. C) nerve cells. D) intestinal cells. E) All of the above.
: C Page Ref: Section 9-5
22) A deficiency in the synthesis of sphingomyelins or cerebrosides will most likely result in the improper formation of A) cell surfaces. B) cell to cell communication. C) nerve cells. D) blood groups. E) All of the above.
: C Page Ref: Section 9-5
25) Cholesterol is converted to cholesteryl esters for ________ in cells and are ________ (more, less) hydrophobic than glycerophospholipids. A) transport; more B) transport; less C) storage; more D) storage; less E) synthesis; more
: C Page Ref: Section 9-6
34) Liposomes consist of ________ bilayers that enclose an aqueous compartment where drugs can be contained for delivery to specific tissues if target proteins are present. A) cholesterol B) membrane protein C) phospholipids D) detergents
: C Page Ref: Section 9-9
36) Diffusion of membrane proteins was demonstrated by fusing human cells and mouse cells that had membrane proteins labeled with ________ of different colors. A) radioactivity B) fluorescent dyes C) fluorescent antibodies D) fluorescent lipids
: C Page Ref: Section 9-9
37) Phospholipids can move from one layer to the other in a cell membrane bilayer by A) lateral diffusion. B) biosynthesis. C) flippases and floppases. D) increased diffusion.
: C Page Ref: Section 9-9
39) Which statement is false about lipid rafts? A) Membrane proteins help maintain the integrity of membrane rafts. B) They are distributed non-uniformly on the mammal cell surfaces. C) They occur mostly on the outer mitochondrial membrane. D) They are patches of cholesterol associated with sphingolipids.
: C Page Ref: Section 9-9
1) Lipids may be either hydrophobic or ________. A) hydrophilic B) amphoteric C) inorganic D) amphipathic
: D Page Ref: 9-Introduction
2) ________ are the simplest lipids but they may be a part of or a source of many complex lipids. A) Triglycerols B) Carbohydrates C) Terpenes D) Fatty acids E) Waxes
: D Page Ref: Section 9-1
3) Isoprenoids are lipids which neither contain nor are derived from fatty acids and include A) steroids. B) waxes. C) terpenes. D) A and C only. E) A, B, and C.
: D Page Ref: Section 9-1
42) When red-blood cells are treated extensively with protease most membrane proteins are broken down into small peptides. However, some proteins are very resistant to this treatment. If cleavage by protease is the only type of reaction that occurs in this treatment, how is this explained? A) They are lipid-anchored membrane proteins. B) They are peripheral proteins. C) They contain at least 2 disulfide bonds. D) They are integral (intrinsic) membrane proteins.
: D Page Ref: Section 9-10
46) Which statement is false about lipid-anchored membrane proteins? A) They are found on either leaflet of the plasma membrane. B) Like integral membrane proteins, they are permanently associated with the membrane. C) The covalent link to the membrane can involve the phosphate group of the lipid anchor. D) The protein portion that can be removed by treatment with phospholipase most resembles an integral membrane protein.
: D Page Ref: Section 9-10
51) Another name for facilitated diffusion is ________. A) active transport B) transverse diffusion C) lateral diffusion D) passive transport
: D Page Ref: Section 9-11
57) Very large molecules (macromolecules) can be transported across membranes by ________. A) pores or channels with very large openings through the center B) active transport proteins C) diffusion down a concentration gradient D) endocytosis or exocytosis
: D Page Ref: Section 9-11
59) Which does not generally use a signal transduction mechanism? A) Hydrophilic hormones. B) Neurotransmitters. C) Growth factors. D) Steroids.
: D Page Ref: Section 9-12
10) Fatty acids required in the diet of mammals are called A) important. B) dietary. C) saturated. D) essential. E) esters.
: D Page Ref: Section 9-2
8) Trans fatty acids have physical properties like those of A) w-3 fatty acids. B) cis-fatty acids. C) unsaturated fatty acids. D) saturated fatty acids.
: D Page Ref: Section 9-2
11) Most lipids in the average human diet are A) unsaturated fatty acids. B) saturated fatty acids. C) glycerophospholipids. D) triacylglycerols.
: D Page Ref: Section 9-3
21) An unknown lipid is treated with a mixture of phospholipases A1, A2, C and D. Since no glycerol is formed after this treatment, the lipid is most likely A) phosphatidylethanolamine. B) phosphatidylcholine. C) plasmologen. D) ceramide. E) a mixture of A and B.
: D Page Ref: Section 9-5
23) Tay-Sachs disease results from A) a deficiency of GM2. B) defective lysosomes. C) malfunction of cerebroside metabolism. D) the accumulation of GM2.
: D Page Ref: Section 9-5
35) What is the role of cholesterol in animal cell membranes? A) Blocks the association of the fatty acyl chains of phospholipids at high temperature. B) Aids in the transport of small hydrophobic molecules across the membrane. C) Is a receptor site for hormones on the surface of membranes. D) Broadens the temperature range of optimum membrane fluidity.
: D Page Ref: Section 9-9
12) Dietary triacylglycerols are digested as a result of A) lipase action. B) bile salts. C) micelle formation. D) diffusion and absorption by intestinal cells. E) All of the above.
: E Page Ref: Section 9-3
13) Adipocytes contain fat droplets which serve to provide an animal with A) increased cell volume. B) insulation. C) chemical energy. D) A and B above. E) B and C above.
: E Page Ref: Section 9-3
16) Polar heads of glycerophospholipids may be A) + charged. B) - charged. C) neutral, but polar. D) a mixture of + and - charges. E) All of the above.
: E Page Ref: Section 9-4
17) Ethanolamine, serine and choline can be cleaved from glycerophospholipids by treatment with A) phospholipase A1. B) phospholipase A2. C) phospholipase B. D) phospholipase C. E) phospholipase D.
: E Page Ref: Section 9-4
30) In a typical eukaryotic plasma membrane, A) oligosaccharides face outward, not toward the cytosol. B) proteins can move within the bilayer. C) lipids can move and diffuse through the bilayer. D) some lipids can rotate within the bilayer. E) All of the above.
: E Page Ref: Section 9-8
31) The arrangement of lipid bilayers and other components is the basis for the currently widely accepted description which is called the A) fluid model. B) lipid bilayer model. C) mosaic model. D) diffusion model. E) fluid mosaic model.
: E Page Ref: Section 9-8
