1. Which is NOT found in a cell membrane?
A. Lipid
B. DNA
C. Protein
D. Cholesterol
B. DNA
2. The cell membrane is NOT involved in:
A. cell communication.
B. import and export of molecules.
C. DNA Replication.
D. cell growth and motility.
C. DNA Replication.
3. The tails of phospholipids are:
A. hydrophobic.
B. hydrophilic.
C. amphipathic.
A. hydrophobic.
4. The entire phospholipid molecule is:
A. hydrophobic. B. hydrophilic. C. amphipathic.
C. amphipathic.
5.Which parts of the phospholipid face the outside of the membrane?
A. The head B. The tail C. The belly
A. The head
6. Why do lipids form bilayers in water?
A. The hydrophobic head is attracted to water while the hydrophilic tail shuns water.
B. The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
C. The hydrophobic tail is attracted to wa
B. The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
7. In a lipid bilayer, which behaves like a two-dimensional fluid, lipids rapidly diffuse:
A. (A) within the plane of one monolayer in the bilayer.
B. (B) back and forth from one monolayer to the other in the bilayer. C. Both A and B
D. Neither A nor B
A. (A) within the plane of one monolayer in the bilayer.
8. In one second, a lipid in an artificial bilayer may diffuse as far as what distance?
A. 2 nanometers (the width of a DNA double helix) B. 2 microns (the length of a large bacterial cell) C. 500 microns (the length of a typical amoeba)
B. 2 microns (the length of a large bacterial cell)
9. Phospholipids with which of the following hydrocarbon tails will produce the most fluid bilayer?
A. Tails with 18 carbon atoms, fully saturated
B. Tails with 18 carbon atoms and two double bonds C. Tails with 20 carbon atoms, fully saturated
D. Tails w
B. Tails with 18 carbon atoms and two double bonds
10. Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment?
A. Decreasing the number of single bonds (i.e., changing them to double bonds and removing hydrogen atoms)
B. The removal of double bonds (i.e., changing the
B. The removal of double bonds (i.e., changing them to single bonds and adding hydrogen atoms)
11. Double bonds in hydrocarbon tails have what effect on the rigidity of fats and phospholipid bilayers?
A. Double bonds increase the ability of hydrocarbon tails to pack together into a rigid mass.
B. Double bonds decrease the ability of hydrocarbon tai
B. Double bonds decrease the ability of hydrocarbon tails to pack together into a rigid mass.
12. How does cholesterol in animal cell membranes affect the fluidity of the bilayer?
A. Cholesterol tends to stiffen the bilayer.
B. Cholesterol tends to make the bilayer more fluid.
C. Cholesterol has little effect on membrane fluidity.
A. Cholesterol tends to stiffen the bilayer.
13. In eukaryotic cells, new phospholipids are manufactured byenzymes bound to which part of the endoplasmic reticulum membrane?
A. The monolayer that faces the lumen of the endoplasmic reticulum
B. The monolayer that faces the cytosol
C. Both monolayers
B. The monolayer that faces the cytosol
14. What type of enzyme moves phospholipids from one monolayer to the other in a biological membrane?
A. Phospholipase
B. Flippase
C. No enzyme-this action happens spontaneously and relatively quickly
B. Flippase
15. When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face:
A. the cell cytoplasm.
B. the outside of the cell.
B. the outside of the cell.
16. How much of the mass of the plasma membranes is constituted by proteins? A. 25%
B. 50%
C. 75%
B. 50%
17. Which of the following is NOT a function of membrane proteins?
A. Transport molecules across the membrane
B. Generate the energy required for lipids to diffuse through the membrane C. Transmit extracellular signals to the cell interior
D. Serve as anc
B. Generate the energy required for lipids to diffuse through the membrane
18. Which is NOT an integral membrane protein?
A. A transmembrane protein that spans the lipid bilayer
B. A monolayer associated protein tucked into the inner leaflet of the lipid bilayer
C. A protein attached to the membrane by non-covalent interactions
C. A protein attached to the membrane by non-covalent interactions with other membrane proteins
19. In the alpha helices of transmembrane proteins, the hydrophobic side chains are facing:
A. the inside of the membrane-spanning helix. B. the outside of the membrane-spanning helix.
B. the outside of the membrane-spanning helix.
20. Porin proteins-which form large, water-filled pores in mitochondrial and bacterial membranes-fold into /beta barrel structures. The amino acids that face the outside of the barrel have what kind of side chains?
A. Hydrophilic B. Hydrophobic
B. Hydrophobic
21. Which statement about phospholipids and detergents is NOT true?
A. Phospholipids have two hydrocarbon tails, whereas detergents have just one. B. Phospholipids are amphipathic, whereas detergents are hydrophobic.
C. Phospholipids form bilayers, wherea
B. Phospholipids are amphipathic, whereas detergents are hydrophobic.
22. Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what?
A. Hydrolyze ATP molecules
B. Pump H+ out of the cell and generate a H+ gradient across the plasma membrane
C. Pump photons into the cell and generate a deep purple color
B. Pump H+ out of the cell and generate a H+ gradient across the plasma membrane
23. The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called:
A. basal lamina.
B. carbohydrate layer. C. cell cortex.
D. tight junction.
C. cell cortex.
24. Which is not a mechanism for restricting the movement of proteins in the membrane?
A. Using barriers such as tight junctions
B. Coating proteins with carbohydrates
C. Tethering proteins to the cell cortex
D. Tethering proteins to the extracellular mat
B. Coating proteins with carbohydrates
25. On what side of the membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located?
A. Cytosolic side
B. External (noncytosolic) side
B. External (noncytosolic) side
26. What do carbohydrates attached to cell-surface proteins and lipids provide a cell?
A. Protection from mechanical and chemical damage
B. A slimy coat that prevents cells from sticking to one another C. A distinctive identity in cell-cell recognition
D.
D. All of the above
27. Which of the following membrane lipids does not contain a fatty acid tail? (a) Phosphatidylcholine
(b) A glycolipid
(c) Phosphatidylserine
(d) Sphingomyelin (e) Cholesterol
(e) Cholesterol
28. Which of the following statements regarding lipid membranes is TRUE?
(a) Phospholipids will spontaneously form liposomes in nonpolar solvents.
(b) In eucaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer.
(c) Membrane lipids
(c) Membrane lipids diffuse within the plane of the membrane.
29. Which of the following statements regarding the fatty acid tails of phospholipids is FALSE?
(a) Phospholipids with unsaturated tails make the bilayer more fluid because the tails contain fewer hydrogen atoms and thus form fewer hydrogen bonds with eac
(a) Phospholipids with unsaturated tails make the bilayer more fluid because the tails contain fewer hydrogen atoms and thus form fewer hydrogen bonds with each other.
30. Fill in the blanks.
The specialized functions of different membranes are largely determined by the __________________ they contain. Membrane lipids are __________________ molecules, composed of a hydrophilic portion and a hydrophobic portion. All cell
30. proteins, amphipathic, lipid bilayer, fatty acid tails, hydrophilic head groups,
phospholipids, sugars
31. Which of the following statements is true?
(a) Phospholipids will spontaneously form liposomes in nonpolar solvents.
(b) In eucaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer.
c) Membrane lipids diffuse within the plane o
(a) Phospholipids will spontaneously form liposomes in nonpolar solvents.
32. Why are glycolipids found on the extracellular, but not the cytoplasmic, surface of the plasma membrane?
(a) Plasma membrane flippases transport them from the cytosolic face.
(b) The enzymes that produce them are present only on the extracellular surf
(c) The enzymes that add the sugar groups are confined to the inside of the endoplasmic reticulum and the Golgi apparatus.
33. A group of membrane proteins, which can be extracted only from membranes using detergents, are all found to have a similar amino acid sequence at their carboxyl terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands
(a) The cysteine residue is covalently attached to a membrane lipid.
34. Select lipids containing a phosphorous atom from the following list.
1. ceramide
2. sphingosine
3. sphingomyelin
4. diacylglycerol
5. ganglioside
6. phosphatidyl serine
7. cholesterol
8. triacylglycerol
3. sphingomyelin
6. phosphatidyl serine
There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called __________________ proteins and have __________________ regions that are exposed to the interior of the
35. transmembrane, hydrophobic, amphipathic, covalently, peripheral
36. Which of the following statements regarding membrane proteins is FALSE?
(a) Integral membrane proteins often precipitate (form insoluble aggregates) in aqueous solutions lacking detergents.
(b) Some hydrophobic amino acids in membrane proteins are not
(e) In transmembrane proteins that form an aqueous pore through the membrane, the pore is lined with hydrophobic amino acid side chains
37. Proteins that form a �-barrel pore in the membrane have several �-strands that span the membrane. The amino acid side chains facing the inside of the pore would be hydrophilic whereas the amino acid side chains facing the lipid bilayer would be hydrop
(a) Ala-Asp-Phe-Lys-Leu-Ser-Val-Glu-Leu-Thr
38. Porin proteins form large, barrel-like channels in the membrane. Which of the following is not true about these channels?
(a) They are made primarily of ? helices.
(b) They are made primarily of ? sheets.
(c) They cannot form narrow channels.
(d) They
(a) They are made primarily of ? helices.
39. Which of the following functions does the cell cortex perform?
(a) It influences the passage of small molecules into and out of the cell.
(b) It allows cells to change shape and to move.
(c) It lubricates the cell.
(d) It restricts the movement of cer
B, D, E
40. Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways?
(a) Varying the types of sugar monomers used
(b) Varying the types of linkages between sugars
(c) Varying
(e) All of the above
41. Red blood cells have been very useful in the study of membranes and the protein components that provide structural support. 1) Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell? 2) Which of the follow
(d) spectrin ,(f) glycoporin
42. Which of the following statements about the carbohydrate coating of the cell surface is FALSE?
(a) It is not usually found on the cytosolic side of the membrane.
(b) It can play a role in cell-cell adhesion.
(c) The arrangement of the oligosaccharide
(c) The arrangement of the oligosaccharide side chains are highly ordered, much like the peptide bonds of a polypeptide chain.
43. Cell membranes are fluid, and thus proteins can diffuse laterally within the lipid bilayer. However, sometimes the cell needs to localize proteins to a particular membrane domain. Name four mechanisms that a cell can use to restrict a protein to a par
43. Tethered to the cell cortex, tethered to extracellular matrix molecules, tethered to
molecules in another cell, diffusion barrier (Figure 11-33)
44. Movement of phospholipids from one leaflet to the other
(a) occurs routinely.
(b) requires cholesterol.
(c) requires flippases.
(d) is impossible.
(c) requires flippases.
45. Cholesterol mixes with phospholipids in a biomembrane because cholesterol molecules are
(a) amphipathic.
(b) steroid derivatives.
(c) entirely hydrophobic.
(d) phospholipid derivatives.
(a) amphipathic.
46. Which of the following classes of lipids is (are) present in biomembranes? (a) phospholipids
(b) sphingolipids
(c) cholesterol
(d) all of the above
(d) all of the above
47. Phospholipids with short or unsaturated fatty acyl chains (a) decrease membrane fluidity.
(b) increase membrane fluidity.
(c) cause biomembranes to become thicker.
(d) allow hydrophilic molecules to diffuse across the lipid bilayer.
(b) increase membrane fluidity.
48. The ___________________________________________ are transmembrane proteins.
(a) lipid-anchored membrane proteins
(b) integral membrane proteins
(c) peripheral membrane proteins (d) extracellular matrix proteins
(b) integral membrane proteins
49. Indicate whether the following statements are true or false. If a statement is false, explain why it is false.
A. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like all other membrane lipids.
B. Phosphatidylserine is
49. A: true, B: false (phosphatidylcholine is the most abundant phospholipid.) C: true, D: false (formation of lipid bilayer is favorable in water.)
50. Sodium dodecyl sulfate (SDS) and Triton X-100 are both detergents that can be used to lyse cells.
A. If the the goal is to study the activity of membrane proteins after cell lysis, explain why SDS would not be a good choice.
B. How does Triton X-100 w
50. A: SDS is a strong ionic detergent. SDS extracts proteins out from the membrane and completely unfolds them. It is impossible to do functional study of the denatured proteins. B: Triton X-100 is a mild detergent having a polar but uncharged portion. T
. Consider the apical location of a particular protein expressed in epithelial cells, illustrated in Figure A. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in Figure B?
(
51. b