self test-4.doc

1.Of the four classes of cellular macromolecules, which one is not a component of cell membranes?A.proteinsB.lipidsC.nucleic acidsD.carbohydrates2.How do membranes function as a locus of biochemical reactions?A.Membranes separate the reactants from the products of enzymatic reactions.B.Membranes hold enzymes of sequential reactions in close proximity.C.Membrane lipids catalyze important cellular reactions.D.Membranes increase the activation energy for catalysis.3.Features of the fluid mosaic model of membrane structure include:A.a lipid bilayer.B.dynamic motion of both membrane lipids and proteins.C.proteins that may either rest on the surface or penetrate the membrane.D.all of the above.4.The relative proportion (by weight) of lipid and protein in a membrane:A.is always about equal.B.varies depending upon the source of the membrane.C.is always characterized by more lipid than protein.D.is always characterized by more protein than lipid.5.Which of the following is not true of membrane phosphoglycerides?A.They include phosphatidylcholine, phosphatidylethanolamine and cholesterol, among others.B.They are amphipathic.C.They have two fatty acids attached to a glycerol molecule, and a polar head group attached via a phosphate.D.They can have both saturated and unsaturated fatty acids.6.Gorter and Grendels earliest evidence that membranes were formed from a lipid bilayer included:A.microscopic examination of red blood cell membranes.B.measuring the surface area of lipids extracted from red blood cells, and comparing that to the surface area of the cells.C.measuring the mobility rates of membrane proteins.D.all of the above.7.Membrane carbohydrates occur as:A.either glycoproteins or glycolipids, but are not free in the membrane.B.either glycoproteins, or free in the membrane, but are not attached to lipids.C.either glycolipids or free in the membrane, but are not attached to proteins.D.none of the above.8.A membrane-affiliated protein is isolated by detergent extraction, and found to be amphipathic and lacking any nonprotein components. To which class of membrane proteins does it belong?A.integral proteinsB.peripheral proteinsC.lipid-anchored proteinsD.none of the above9.Site-directed cross-linking is a technique that gives insight into what property of integral membrane proteins?A.number of transmembrane domainsB.on which side of the membrane the N and C termini are foundC.proximity of various membrane-spanning domains to each otherD.none of the above10.A membrane is examined using freeze-fracture and freeze-etch analysis. The surfaces are shown to have almost no pits or bumps. Which of the following is the most likely source of the membrane?A.mitochondria, inner membraneB.myelinC.red blood cellD.all of the above11.Which one of the following organisms would you predict has the highest proportion of unsaturated fatty acids in their membranes?A.Antarctic fishB.cactusC.bacteria from thermal hot springsD.humans12.Which of the following statements about the mobility of membrane components is true?A.Proteins and lipids move equally rapidly within the plane of the membrane.B.Lipids generally move more rapidly than proteins within the plane of the membrane.C.Proteins generally move more rapidly than lipids within the plane of the membrane.D.Lipids and proteins “flip-flop” between membrane leaflets more readily than they move within the plane of the membrane.13.Substance X is a charged molecule of small molecular weight. It is found at higher concentrations outside of cells than inside. How might substance X enter cells?A.diffusion through a channelB.diffusion through the lipid bilayerC.active transportD.none of the above14.The distribution of K+ across an artificial membrane was measured, and the concentrations were found to be equal on both sides. Which of the following statements is true about the distribution of K+?A.K+ must be at equilibrium across the cell membrane.B.K+ cannot be at equilibrium across the membrane.C.There cannot be a membrane potential under these conditions.D.More information is needed to determine whether K+ is at equilibrium.15.If a freshwater plant were put in sea water, its cells would:A.undergo plasmolysis.B.lyse.C.swell with turgor pressure.D.all of the above.16.The cell in number (15) above would be in an environment that was:A.hypertonic.B.hypotonic.C.isotonic.D.hypo-osmotic.17.Which of the following is an example of an ion transporter?A.Na+-K+ ATPaseB.ABC transporterC.CFTRD.all of the above18.Arrange the statements below in the proper sequence of events that occur in an action potential: I.The resting potential is reestablished.II.A stimulus depolarizes the membrane to threshold.III.Na+ gates open and Na+ rushes into the cell.IV.K+ gates open and K+ rushes out of the cell.A.II, III, IV, IB.III, IV, II, IC.II, IV, III, ID.I, II, IV, III19.A neurotransmitter that binds to a postsynaptic cell and opens K+ channels:A.excites the postsynaptic cell.B.inhibits the postsynaptic cell.