50. The Na+/K+ pump creates a ____ charge inside the cell and a ____ charge outside the cell.
a.
negative; negative
b.
positive; negative
c.
positive; positive
d.
negative; positive
e.
neutral; positive
51. A(n) ____ is created as ions diffuse across membranes.
a.
chemical gradient
b.
electrochemical gradient
c.
negative gradient
d.
electrical gradient
e.
concentration gradient
52. A transport system in which transport of an ion in one direction provides the energy for active
transport in the opposite direction is known as ____.
a.
antiport
b.
active diffusion
c.
symport
d.
cotransport
e.
osmosis
53. Cells undergo exocytosis ____.
a.
to pump protons down a concentration gradient
b.
when replicating
c.
to secrete protein and wastes from the cell
d.
to ingest nutrients
e.
as a means of cellular protection
54. Eukaryotic cells import large molecules through the process of ____ and secrete larger molecules by
____.
a.
endocytosis; exocytosis
b.
diffusion; exocytosis
c.
exocytosis; endocytosis
d.
endocytosis; phagocytosis
e.
phagocytosis; pinocytosis
55. Pinocytosis and phagocytosis are accomplished in the cell by the ____.
a.
nucleus
b.
lysosome
c.
endoplasmic reticulum
d.
plasma membrane
e.
mitochondria
56. Which process is responsible for the movement of solids into some animal cells?
a.
pinocytosis
b.
osmosis
c.
receptor-mediated endocytosis
d.
facilitated diffusion
e.
phagocytosis
57. What is the molecular basis of familial hypercholestremia?
a.
HDL enters cells using a specific receptor
on the cell surface
d.
LDL exits cells using a specific receptor
on the cell surface
b.
LDL enters cells using a specific receptor
on the cell surface
e.
receptor-mediated exocytosis
c.
HDL exits cells using a specific receptor
on the cell surface
58. Aquaporins are ____.
a.
pores made of water molecules
b.
proteins utilized to transport water molecules
c.
found only in bacterial cells
d.
specific channels for water transport
e.
useful for cell signaling
59. Humans with mutations in the gene encoding AQP1 (aquaporin-1) that cause the absence of AQP1are
characterized by an inability to ____.
a.
concentrate urine despite prolonged
thirsting
d.
control sweating
b.
control edema
e.
salivate
c.
make large volumes of dilute urine
60. Carrier molecules are utilized for ____.
a.
active transport only
b.
passive transport only
c.
both active and passive transport
d.
osmosis
e.
transport of all types of molecules
61. The selective permeability of a cell membrane is due to ____.
a.
the hydrophobic core formed by the phospholipid tails
b.
the hydrophilic end facing the cell exterior
c.
glycolipids on the surface of the membrane
d.
the position of cholesterol in the membrane bilayer
e.
the hydrophilic core formed by the phospholipid tails
Select the Exception
62. All of the following are functions of integral membrane proteins EXCEPT ____.
a.
transport of polar molecules
b.
reception of chemical signals form other cells
c.
cell division
d.
recognition of other cells as being “like”
e.
cell-cell binding
63. Each of the following characteristics is true for both facilitated diffusion and active transport EXCEPT
____.
a.
the use of transport proteins is required
b.
transport proteins are specific for the molecules being transported
c.
transport proteins can become saturated
d.
a concentration gradient is present
e.
the direction of transport is always with the concentration gradient
64. Each of the following small molecules easily diffuses through the cell membrane EXCEPT ____.
a.
steroid hormones
b.
O2
c.
H2O
d.
glucose
e.
CO2
65. All of the following describe facilitated diffusion EXCEPT ____.
a.
it is specific
b.
it is dependent on a concentration gradient
c.
it requires ATP
d.
it can involve either carrier proteins or channel proteins
e.
it involves integral proteins
66. Examples of molecules secreted from a eukaryotic cell by exocytosis include all of the following
EXCEPT ____.
a.
insulin
b.
ions
c.
milk proteins
d.
mucus
e.
digestive enzymes
MATCHING
Match each of the following mechanisms of cellular transport with its correct definition.
a.
Movement of a molecule from an area of high concentration to an area of lower
concentration.
b.
Cells internalize molecules into a cell by the inward budding of vesicles possessing
receptors specific to the molecule being transported.
c.
Movement of water from a hypotonic solution into a hypertonic solution across a
selectively permeable membrane.
d.
Large particles are enveloped by the cell membrane and internalized.
e.
A process in which liquid droplets are ingested by living cells.
f.
Diffusion of molecules across the plasma membrane with the assistance of transport
proteins.
67. osmosis
68. facilitated diffusion
69. phagocytosis
70. pinocytosis
71. receptor-mediated endocytosis
72. diffusion
143
Labeling
Identify each structure found in a typical plasma membrane in the figure below.
73. Microfilament
74. Carbohydrate groups
75. Integral proteins
76. Peripheral proteins
77. Cholesterol
Labeling
The micrographs of animal cells depict the effects of various aqueous environments on red blood cells
placed in a hypotonic, hypertonic and isotonic environment. Identify the correct term below.
78. Isotonic
79. Hypertonic
80. Hypotonic
SHORT ANSWER
81. What does the high similarity of bilayer membranes in all cells indicate?
82. How does the freeze-fracture technique confirm that the fluid membrane is a bilayer with proteins
suspended in it individually?
145
83. Explain why the transport of molecules across the cell membrane is considered to be both specific and
directional.
84. Water is a strongly polar molecule, so how does it cross the plasma membrane?
85. Carrier proteins share several characteristics with enzymes used to catalyze metabolic reactions. In
what ways are carrier proteins and enzymes similar?
OTHER
86. Arrange the following steps involved in secondary active transport in the correct order. Write the letter
of the first step next to 1 and the letter of the last step next to 5.
A.
B.
C.
D.
E.
1.
2.
3.
4.
5.
MODIFIED TRUE/FALSE
If the statement is true, answer “T“. If the statement is false, answer “F” and make it correct by
changing the underlined word(s) and writing the correct word(s) in the answer blank(s).
87. Particular mutations in the cystic fibrosis transmembrane conductance (CFTR) gene result in a CFTR
molecule that transports sodium ions poorly or not at all.
88. A water concentration gradient is influenced by the number of solute molecules present on both sides
of the membrane.
89. An animal cell placed in a hypertonic solution will swell and perhaps burst.
90. Physiological saline is 0.9 percent NaCl; red blood cells placed in such a solution will not gain or lose
water; therefore, one could state that the fluid in red blood cells is hypertonic.
91. A solution of 65 percent water, 35 percent solute is more concentrated with respect to solute than a
solution of 70 percent water, 30 percent solute.
92. A hypertonic environment would be ideal for a healthy plant.
93. In primary active transport, the carrier protein that transports a substance also hydrolyzes ATP to
power the transport directly.
94. Cholesterol is essential for keeping cell membranes from thickening.
ESSAY
95. Explain what occurs when the cystic fibrosis transmembrane conductance regulator (CFTR) gene
contains a mutation.
96. Distinguish between the structure and function of integral membrane proteins and peripheral
membrane proteins.