Biology Chapter 7 MC
Which component in the accompanying figure is a protein fiber of the extracellular matrix?
A
Which of the following statements is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
Which component in the accompanying figure plays a critical role in cell-cell recognition?
B
Which component in the accompanying figure is a microfilament (actin filament) of the cytoskeleton?
C
In what way do the membranes of a eukaryotic cell vary?
Certain proteins are unique to each membrane.
Which component in the accompanying figure is cholesterol?
D
Which component in the accompanying figure is hydrophilic? A) A
D
For a protein to be an integral membrane protein, it would have to be ________.
amphipathic, with at least one hydrophobic region
According to the fluid mosaic model of cell membranes, phospholipids ________.
can move laterally along the plane of the membrane
What kinds of molecules pass through a cell membrane most easily?
large polar
Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. Unknown Percent change in mass Percent change in mass Percent change in mass Group 1 Group 2 Group 3 A 6.6 7.8 7.5 B 3.1 3.7 2.9 C -2.7 -3.5 -2.5 D 0.7 0.5 1.1 E -11.6 -12.3 -12.6 F -5.2 -6.2 -4.9 Based on the data provided, the intracellular molarity of dissolved solutes in sweet potato cells is approximately ________.
0.4 M
The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. When the system illustrated above reaches equilibrium, the sugar concentrations on both sides of the U-tube will be ________.
1.5 M sucrose, 1.5 M glucose
Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed. Which line in the graph represents the bag with the highest initial concentration of sucrose?
A
Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic at 50 minutes?
B
Five dialysis bags, constructed of a type of membrane that is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed), and the percent change in mass of each bag was graphed. Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?
C
Which of the following statements correctly describes osmosis?
In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.
Which of the following statements describes a characteristic feature of a carrier protein in a plasma membrane?
It exhibits specificity for a particular type of molecule.
Which of the following statements about diffusion is true?
It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
Which of the following would likely diffuse through the lipid bilayer of a plasma membrane most rapidly?
O2
Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and -1.0 M. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data given, which statement most accurately describes what is occurring in response to a particular unknown solution?
Osmosis of water molecules from unknown solution B likely caused the increase in mass observed.
A phospholipid bilayer with equal amounts of saturated and unsaturated fatty acids displays a specific permeability to glucose. What effect will increasing the proportion of unsaturated fatty acids in the bilayer have on the membrane's permeability to glucose?
Permeability to glucose will increase.
When a plant cell, such as one from a tulip leaf, is submerged in a hypertonic solution, what is likely to occur?
Plasmolysis will shrink the interior of the cell.
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this fact most probably mean?
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. At the beginning of the U-tube experiment illustrated above, which of the following statements is true?
Side A is hypotonic to side B.
What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?
The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC.
The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. In the U-tube experiment illustrated above, which of the following statements correctly describes side B at equilibrium?
The concentration of NaCl will increase, the concentration of glucose will decrease, and the water level will increase.
Which of the following statements is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?
The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.
A patient was involved a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?
The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.
What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV is endocytosed first, and then later fuses with the endocytotic vesicle membrane?
The red fluorescent dye-labeled lipids will appear in the infected cell's interior.
Cell membranes have distinct inside and outside faces. Which of the following statements is the most likely explanation for the membrane's asymmetrical nature?
The two sides of a cell membrane face different environments and carry out different functions.
The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. Which of the following will be true when the system illustrated above reaches equilibrium?
The water level will be higher in side A than in side B.
Why are lipids and proteins free to move laterally in membranes?
There are only weak hydrophobic interactions in the interior of the membrane.
When a cell is in equilibrium with its environment, which of the following processes occurs for substances that can diffuse through the plasma membrane?
There is random movement of substances into and out of the cell.
The force driving simple diffusion is ________, while the energy source for active transport is ________.
a concentration gradient; ATP hydrolysis
Which of the following factors would tend to increase membrane fluidity?
a greater proportion of unsaturated phospholipids
Which of the following structures would decrease the electrochemical gradient across a membrane?
a potassium channel
In which of the following environments would there be the greatest need for osmoregulation?
a salmon moving from a river into an ocean
Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells? The animal cell is in ________.
an isotonic solution, and the plant cell is in a hypotonic solution
Which of the following molecules dramatically increases the rate of diffusion of water across cell membranes?
aquaporins
In an HIV-infected cell producing HIV virus particles, the viral glycoprotein is expressed on the plasma membrane. How do the viral glycoproteins get to the plasma membrane? They are synthesized ________.
by ribosomes in the rough ER and arrive at the plasma membrane in the membrane of secretory vesicles
An animal cell lacking carbohydrates on the external surface of its plasma membrane would likely be impaired in which function?
cell-cell recognition
Which of the following types of molecules lack hydrophilic domains?
cholesterol
The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membrane—more acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of ________.
cotransport
In some cells, there are many ion electrochemical gradients across the plasma membrane even though there are usually only one or two proton pumps present in the membrane. The gradients of the other ions are most likely accounted for by ________.
cotransport proteins
Based on Figure 7.18, which of these experimental treatments would increase the rate of sucrose transport into a plant cell?
decreasing extracellular pH
Familial hypercholesterolemia is characterized by ________.
defective LDL receptors on the cell membranes
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly
embedded in a lipid bilayer.
Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following types of treatments?
hydrating drinks with high concentrations of salt and glucose
The membranes of winter wheat are able to remain fluid when it is extremely cold by ________.
increasing the proportion of unsaturated phospholipids in the membrane
Diffusion of ions across membranes through specific ion channels is driven by ________.
ion electrochemical gradients
According to the fluid mosaic model, a membrane ________.
is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins
Celery stalks that are immersed in fresh water for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the fresh water ________.
is hypotonic and the salt solution is hypertonic to the cells of the celery stalks
The sodium-potassium pump is called an electrogenic pump because it ________.
is used to drive the transport of glucose against a concentration gradient
A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in ________.
lysosomes
The voltage across a membrane is called the ________.
membrane potential
Which of the following membrane activities requires energy from ATP hydrolysis?
movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
A sodium-potassium pump ________.
moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis
In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?
on the inside surface of the vesicle
Which of the following processes includes all of the others?
passive transport
Which of the following processes includes all the others?
passive transport
Which of the following types of molecules are hydrophilic and therefore excluded from the hydrophobic portion of the phospholipid bilayer?
peripheral membrane proteins
An organism with a cell wall would most likely be unable to take in materials through ________.
phagocytosis
White blood cells engulf bacteria using ________.
phagocytosis
The difference between pinocytosis and receptor-mediated endocytosis is that ________.
pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity
The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. In the U-tube illustrated above, ________.
side A is isotonic to side B
A research team is working on the design of a new drug for the treatment of lung cancer. To be most effective, this drug must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug?
similarity of the drug molecule to other molecules normally transported lung cells
Which of the following are least likely to diffuse through the phospholipid bilayer of a cell membrane?
small ions