Chapter 11- Membrane Structure
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
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 check my answer
A
The tails of phospholipids are: A. hydrophobic. B. hydrophilic. C. amphipathic.
A
Which parts of the phospholipid face the outside of the membrane? A. The head B. The tail C. The belly
A
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 D. Convert CO2 into sugar during photosynthesis
B
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 tails to pack together into a rigid mass. C. Double bonds have little effect on the rigidity of fats and phospholipid bilayers.
B
How much of the mass of the plasma membranes is constituted by proteins? A. 25% B. 50% C. 75%
B
In eukaryotic cells, new phospholipids are manufactured by enzymes 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
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
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
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 them to single bonds and adding hydrogen atoms) C. The addition of carbon atoms D. The removal of carbon atoms
B
On what side of the membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located? A. Cytosolic side B. External (noncytosolic) side
B
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 with 20 carbon atoms and two double bonds
B
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
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
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
Which is NOT found in a cell membrane? A. Lipid B. DNA C. Protein D. Cholesterol
B
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 matrix E. Tethering proteins to the surface of another cell
B
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 anchors to attach the cell to the extracellular matrix
B
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, whereas detergents tend to form micelles. check my answer
B
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 water while the hydrophilic head shuns water. D. The hydrophobic head shuns water and the hydrophilic tail attracts water.
B
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
The entire phospholipid molecule is: A. hydrophobic. B. hydrophilic. C. amphipathic.
C
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
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 with other membrane proteins D. A lipid-linked protein anchored to the outer leaflet of the membrane
C
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. All of the above
D
