CHAPTER 6—MEMBRANES AND TRANSPORT
MULTIPLE CHOICE
1. Organisms must constantly bring in certain molecules and ions while keeping others out. This function
is accomplished by ____.
a.
the nucleus
b.
lysosomes
c.
vesicles
d.
the plasma membrane
e.
the Golgi complex
2. The major structural components of a cell membrane are ____.
a.
phospholipids and cellulose
b.
phospholipids, protein, and sterols
c.
protein and sterols
d.
glycolipids and proteins
e.
phospholipids and glycolipids
3. The polar end of a phospholipid ____.
a.
is in contact with an aqueous solution
b.
does not mix with water
c.
is composed of a phosphate group linked to an alcohol or amino acid
d.
is soluble in water
e.
more than one answer is correct
4. According to the fluid mosaic model of cell membranes, which of the following is true regarding
membrane phospholipids?
a.
They are anchored in place by intermediate filaments.
b.
They can move laterally along the plane of the membrane.
c.
They have hydrophilic tails in the interior of the membrane.
d.
They occur in an uninterrupted bilayer, with membrane proteins bound only to the surface
of the membrane.
e.
They are free to leave the membrane and dissolve in the interstitial fluid.
5. Membrane sterols such as cholesterol function in animal cell membranes to ____.
a.
increase the rate of diffusion
b.
store cellular energy
c.
facilitate ion transport
d.
maintain membrane fluidity
e.
receive chemical signals
6. According to the fluid mosaic model of cell membranes, the fluid part of the model refers to ____.
a.
the constant movement of the hydrophilic tails in the interior of the membrane
b.
a thin layer of water found sandwiched between the two layers of phospholipids
c.
the phospholipid molecules which vibrate, spin, and exchange places within the same
layer of the bilayer
d.
the free movement of cholesterol molecules within the membrane
e.
the frequent flip-flop of phospholipids from one side of the membrane to the other
7. Which type of lipid is most important in the structure of biological membranes?
a.
fat
b.
wax
c.
phospholipid
d.
neutral fat
e.
triglyceride
8. In an aqueous environment, the phospholipids of a membrane ____.
a.
are arranged in a single layer
b.
are arranged in a bilayer with the polar heads of each layer located at the surface
c.
are arranged in a bilayer with the fatty acid tails located at the surface
d.
are arranged in a bilayer but the phospholipids have no specific orientation
e.
dissolve
9. Which of the following molecules demonstrate dual solubility characteristics?
a.
sterols only
b.
proteins only
c.
phospholipids only
d.
sterols and phospholipids
e.
sterols, phospholipids, and proteins
10. When referring to membrane glycolipids and glycoproteins, the term “glyco-” indicates ____.
a.
nonpolar carbohydrate groups are attached to the molecules
b.
polar carbohydrate groups are attached to the molecules
c.
the molecules are found on both the interior and exterior of the membrane
d.
the molecules are attached to the membrane by ionic bonds
e.
the molecules are rarely found on the membrane exterior
11. Our current view of membrane structure is based on the fluid mosaic model, proposed by ____ in
1972.
a.
H. Davson and J. Danielli
b.
I. Langmuir
c.
C. Overton
d.
S. Singer and G. Nicolson
e.
E. Gorter and F. Grendel
12. How are the membranes of many eukaryotic organisms able to remain fluid when the temperature
becomes extremely cold?
a.
The percentage of unsaturated fatty acids in the membrane is increased.
b.
The percentage of saturated fatty acids in the membrane is increased.
c.
The percentage of cholesterol molecules in the membrane is increased.
d.
The percentage of both unsaturated fatty acids and cholesterol is increased.
e.
The percentage of both saturated fatty acids and cholesterol is increased.
13. The “mosaic” part of the fluid mosaic model refers to the membrane ____.
a.
proteins
b.
phospholipids
c.
cholesterol
d.
functions
e.
layers
14. Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a
membrane more fluid at lower temperatures?
a.
The double bonds form a kink in the fatty acid tail, forcing adjacent phospholipids to be
spaced further apart.
b.
Unsaturated fatty acids have a higher cholesterol content.
c.
Unsaturated fatty acids permit more water in the interior of the membrane.
d.
The double bonds block interaction among the hydrophilic head groups of the lipids.
e.
The double bonds result in a shorter fatty acid tail.
15. When comparing the outside and inside halves of a cell membrane’s phospholipid bilayer, the
composition of lipids on the two surfaces is ____.
a.
asymmetrical
b.
identical
c.
not identical, but symmetrical
d.
highly random and varies throughout the cell
e.
a mirror image
16. Which of the following functions is NOT performed by integral membrane proteins?
a.
cell adhesion
b.
transport
c.
signal reception
d.
cell recognition
e.
cell reproduction
17. The ____ component of the cell membrane functions as a selective barrier, while the ____ component
has specific functions such as transport, recognizing other cells, and binding to other cells.
a.
carbohydrate, nucleic acid
b.
protein, lipid
c.
lipid, protein
d.
lipid, carbohydrate
e.
carbohydrate, protein
18. In what way do the various membranes of a cell differ?
a.
Phospholipids are found only in certain membranes.
b.
Certain proteins are unique to each membrane.
c.
Only certain membranes are constructed from molecules with dual solubility.
d.
Only certain membranes of a cell are selectively permeable.
e.
Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have
hydrophilic surfaces facing the cytoplasm.
19. A scientist fused a mouse cell and a human cell, then treated the cell with specific antibodies
covalently linked to fluorescent dyes (antibodies to mouse proteins—green; antibodies to human
proteins—red). What does the cell look like immediately after fusion?
a.
The cell is half red and half green.
b.
The red and green fluorescent labels are uniformly distributed across the entire membrane.
c.
The red and green labels are distributed in intermingled patches.
d.
The red and green labels flash intermittently.
e.
The red and green labels are distributed in a swirling pattern
20. A scientist fused a mouse cell and a human cell, then treated the cell with specific antibodies
covalently linked to fluorescent dyes (antibodies to mouse proteins—green; antibodies to human
proteins—red). Forty minutes later, the researcher looked at the fused cell and observed ____.
a.
the cell was still half red and half green.
b.
the red and green fluorescent labels were uniformly distributed across the entire membrane
c.
the red and green labels were distributed in intermingled patches
d.
the red and green labels flashed intermittently
e.
the red and green labels were distributed in a swirling pattern
21. Reduction of environmental temperatures to freezing rapidly leads to cell death as a result of ____.
a.
inhibition of cell division
b.
inhibition of molecule transport across the cell membrane
c.
increased cellular signaling
d.
increase in metabolic reactions
e.
decreased lipid synthesis
22. Which of the following adaptations to the plasma membrane allows mammals to hibernate in subzero
temperatures without their plasma membranes freezing?
a.
Increase in cholesterol content only.
b.
Increase in protein content only.
c.
Increase in the number of double covalent bonds in phospholipids.
d.
Increase in both cholesterol and protein content.
e.
Increase in both cholesterol and double covalent bonds in phospholipids.
23. The selective permeability of a membrane refers to ____.
a.
the movement of a molecule from an area of greater concentration to an area of lesser
concentration.
b.
the ability of a substance to pass through a membrane
c.
the ability of only certain molecules to pass across a membrane
d.
the need for carrier proteins to transport some molecules
e.
the ability of molecules to be transported across the membrane only certain times of the
day
24. The primary function of cellular membranes is ____.
a.
the controlled transport of ions and molecules across the membrane
b.
cell-cell binding
c.
recognition of other cells as being “like”
d.
reception of chemical signals form other cells
e.
participation in metabolic reactions
25. Movement of a substance from an area of low concentration to an area of high concentration using
energy obtained from ATP is called ____.
a.
passive transport
b.
diffusion
c.
facilitated transport
d.
osmosis
e.
active transport
26. When a drop of food coloring is placed in a container of clear water, the colored dye molecules ____.
a.
undergo osmosis to a different location
b.
undergo active transport to a different location
c.
diffuse to the top of the container
d.
diffuse equally throughout the container
e.
stay at the bottom of the container
27. The concentration gradient that drives diffusion is a form of ____.
a.
heat
b.
potential energy
c.
kinetic energy
d.
active transport
e.
osmosis
28. ____ molecules pass through a cell membrane most easily by diffusion.
a.
ionic
b.
large, polar
c.
large, hydrophilic
d.
small, hydrophobic
e.
large, hydrophobic
29. A channel that opens in response to changes in ionic charge across a membrane is called a ____.
a.
voltage-gated channel
b.
ligand-gated channel
c.
charge-gated channel
d.
electric-gated channel
e.
positive-gated channel
30. Transport of a molecule across a cell membrane by facilitated diffusion ____.
a.
does not exhibit specificity for a particular type of molecule
b.
requires the input of energy
c.
depends on a concentration gradient
d.
goes against the concentration gradient
e.
allows non-polar uncharged molecules to diffuse across a membrane
31. Which one of the following is absolutely necessary for diffusion to occur?
a.
a living cell
b.
a phospholipid bilayer
c.
a selectively permeable membrane
d.
a concentration gradient
e.
a solution
32. Small polar and charged molecules typically cross the cell membrane by way of ____.
a.
simple diffusion
b.
osmosis
c.
filtration
d.
active transport
e.
facilitated diffusion
33. Facilitated diffusion is specific. This means ____.
a.
a specific protein will transport certain polar or charged molecules but not others
b.
that only one specific integral protein per membrane is involved in facilitated diffusion
c.
that the energy molecule ATP is specifically required for transport
d.
only specific hydrophobic molecules can be transported
e.
that transport of molecules occurs only in specific cells
34. Carrier proteins are often used by the cell to transport ____.
a.
H2O
b.
proteins
c.
glucose and amino acids
d.
steroid hormones
e.
CO2
35. Gated channels are NOT utilized by the cell ____.
a.
to transport water
b.
to stimulate muscle contraction
c.
to generate nerve signals
d.
for facilitated diffusion
e.
to transport sodium
36. The movement of water across a membrane from an area of high to low water concentration is an
example of ____.
a.
active transport
b.
endocytosis
c.
osmosis
d.
both osmosis and active transport
e.
both diffusion and osmosis
37. The movement of water across a membrane from an area of lower solute concentration to a region of
higher solute concentration is called ____.
a.
osmosis
b.
active transport
c.
endocytosis
d.
both diffusion and osmosis
e.
both osmosis and active transport
38. The force that pushes plant cells tightly against the cell wall and helps support softer tissues against the
force of gravity is
a.
turgor pressure.
b.
isotonic pressure.
c.
diffusion pressure.
d.
concentration pressure.
e.
plasmolysis pressure.
39. A red blood cell was placed in a beaker of solution. The cell immediately began to swell and
ultimately burst. This happened because the cytoplasm of the cell was ____ to the solution in the
beaker which was ____.
a.
hypertonic; hypotonic
b.
hypotonic; hypertonic
c.
hypotonic; isotonic
d.
hypertonic; isotonic
e.
isotonic; hypotonic
40. When a plant cell is placed in a hypotonic solution, the cell wall prevents ____.
a.
plasmolysis
b.
diffusion
c.
active transport
d.
the cell from bursting
e.
the cell from shrinking
41. Distilled water would be considered ____ to body cells.
a.
isotonic
b.
hypertonic
c.
hypotonic
d.
protonic
e.
aquatonic
42. A(n) ____ environment is ideal for plant cells, while a(n) ____ environment is best for animal cells.
a.
isotonic; hypotonic
b.
hypotonic; isotonic
c.
hypotonic; hypertonic
d.
hypertonic; isotonic
e.
isotonic; isotonic
43. For osmosis to occur, ____.
a.
a selectively permeable membrane must be present
b.
a concentration gradient cannot exist
c.
cellular energy must be expended
d.
pure water must be on one side of the membrane
e.
only solutes can pass through the membrane
44. In plants, wilting of leaves and stems results from ____.
a.
hemolysis
b.
an increase in turgor pressure
c.
plasmolysis
d.
a lack of solutes in the cell
e.
a higher than normal concentration of water in the cell
45. An isotonic solution has a solute concentration ____ to the solute concentration inside the cell.
a.
equal
b.
greater than
c.
less than
d.
it would depend on the solute
e.
it would depend on the type of cell
46. The voltage across a membrane is called the ____.
a.
electrochemical gradient
b.
turgor pressure
c.
membrane potential
d.
chemical gradient
e.
electron potential
47. ____ is the net movement of molecules or ions from a low concentration to a higher concentration.
a.
active transport
b.
facilitated diffusion
c.
exocytosis
d.
osmosis
e.
diffusion
48. Which of the following moves materials against a concentration gradient?
a.
active transport
b.
dialysis
c.
facilitated diffusion
d.
simple diffusion
e.
osmosis
49. The ____ is responsible for maintaining the membrane potential across the cell membrane.
a.
H+ pump
b.
Na+/K+ pump
c.
diffusion gradient
d.
Ca2+ pump
e.
osmotic ratio