Chapter 15 Flashcards
(102 cards)
1
Q
Caveolae are rich in cholesterol and other constituents of lipid rafts.
A
t/f
2
Q
Defects in the human LDL receptor can cause the disease hypercholesterolemia.
A
t/f
3
Q
Phagocytosis is an example of macropinocytosis.
A
t/f
4
Q
The K+-glucose transporter is an example of a symport that actively transports glucose into cells.
A
t/f
5
Q
The major ATPase maintaining the plasma membrane potential is the Na+-K+ pump.
A
t/f
6
Q
Facilitated diffusion is a lipid-mediated process.
A
t/f
7
Q
Estrogen is an example of a hormone to which the plasma membrane is impermeable.
A
t/f
8
Q
The apical surface of intestinal epithelial cells is covered by a carbohydrate coat known as the glycocalyx.
A
t/f
9
Q
The outer membrane of mitochondria is the major site where porins are found in animal cells.
A
t/f
10
Q
Phosphatidylcholine is the only major phospholipid in the plasma membrane.
A
t/f
11
Q
Glycolipids are the major lipids in the plasma membrane.
A
t/f
12
Q
What is the mechanism by which cells take up specific macromolecules?
A
a
13
Q
Where is clathrin located in cells?
A
a
14
Q
Describe a role or function for coated pits in the process of receptor-mediated endocytosis.
A
a
15
Q
Define endocytosis and explain the process by which it operates.
A
a
16
Q
Explain how phagocytosis differs mechanistically from other types of endocytosis.
A
a
17
Q
How is rapid transport of water across the plasma membrane achieved?
A
a
18
Q
How does the structure of a transport protein such as a glucose transporter create an aqueous environment in which glucose may be transported across the plasma membrane?
A
aa
19
Q
What is one function of cell-surface carbohydrates?
A
a
20
Q
Frye and Edidin demonstrated the mobility of membrane proteins with the use of fused human and mouse cells. Briefly describe the results of their experiment.
A
a
21
Q
What are peripheral membrane proteins?
A
a
22
Q
What are integral membrane proteins?
A
a
23
Q
Some endocytic receptors are _______ from endosomes, while others are _______ in lysosomes.
A
a
24
Q
The cytoplasmic domain of ligand-bound LDL receptor binds to _______ proteins, which in turn associate with the _______ coat
A
a
25
Active transport can be driven by _______ hydrolysis or by _______ gradients.
a
26
The plasma membrane of intestinal epithelial cells is divided into two domains: the _______ domain and the _______ domain.
a
27
Some plasma membrane proteins are immobilized by association with proteins, other plasma membrane _______ proteins, and the _______ matrix.
a
28
The membrane-spanning portion of the protein porin (and proteins with similar structures in the outer membranes of mitochondria and chloroplasts) has a membrane-spanning secondary structure called a(n) _______.
a
29
The membrane-spanning portion of a single-pass transmembrane protein is usually a secondary structure called a(n) _______.
a
30
Coated pits are converted to coated vesicles by formation of rings of the protein
Question 42 options:
caveolin.
clathrin.
COPI.
dynamin.
a
31
Brown and Goldstein discovered the mechanism of cholesterol uptake by studying fibroblasts from patients with which disease?
Question 41 options:
Chronic fatigue syndrome
Familial hypercholesterolemia
Lupus erythematosis
Cystic fibrosis
a
32
Cholesterol is taken up into most cells of the body by
Question 40 options:
phagocytosis.
receptor-mediated endocytosis.
simple diffusion.
caveolae formation.
a
33
Phagocytosis is the main function of what two types of human white blood cells?
Question 39 options:
Macrophages and T lymphocytes
Platelets and neutrophils
Macrophages and neutrophils
Eosinophils and T lymphocytes
a
34
Aged red blood cells are removed from circulation by macrophages in the
Question 38 options:
bone marrow.
lymph nodes.
spleen.
kidney
a
35
Phagocytosis involves movement of the cell surface by
Question 37 options:
actin-based motility.
microtubule-based motility.
clathrin-based vesicle formation.
dynamin-based vesicle formation.
a
36
The functioning of the Na+-Ca2+ transporter in the plasma membrane is an example of
Question 36 options:
facilitated diffusion.
symport.
antiport.
endocytosis.
a
37
Coupled transport of glucose and Na+ into the intestinal epithelial cell is an example of
Question 35 options:
facilitated diffusion.
symport.
antiport.
endocytosis.
a
38
Bacteria, fungi, and plants use a gradient of _______ ions across their plasma membranes to drive transport of other molecules into the cells.
Question 34 options:
Na+
K+
H+
Ca2+
a
39
Calcium levels remain low in the cytosol
Question 33 options:
only to ensure that calcium does not precipitate inside the cells.
thus transient calcium increases can be used as intracellular signals.
so that calcium does not accumulate in mitochondria.
to allow extracellular calcium to drive import of other ions.
a
40
What percent of the ATP in a typical animal cell is consumed by the Na+-K+ pump?
Question 32 options:
1%
10%
25%
66%
a
41
The Na+ and K+ ion gradients across the plasma membrane are produced primarily by the
Question 31 options:
permeability of these ions across the lipid bilayer.
ratio of these ions in the blood.
action of the Na+-K+ pump.
flow of these ions through voltage-gated channels.
a
42
Active transport is transport in an energetically
Question 30 options:
unfavorable direction, always driven by hydrolysis of ATP.
unfavorable direction, always coupled to another reaction or source of energy.
unfavorable direction, driven only by the flow of another molecule across a membrane.
favorable direction, coupled to the hydrolysis of ATP.
a
43
Gene therapy for cystic fibrosis involves transfer of the _______ gene into bronchial epithelia.
Question 29 options:
CFTR
mucin
Na+-K+ pump
MDR transporter
a
44
Cystic fibrosis is a genetic disease in which thick mucus accumulates over several types of epithelial cells, eventually blocking the pulmonary airways. The molecular basis of this disease is the production of a defective
Question 28 options:
mucin.
chloride channel.
Na+-K+ pump.
Na+-Ca2+ transporter.
a
45
Voltage-sensitive K+ channels are 1,000 times more permeable to K+ than to Na+ because
Question 27 options:
K+ ions are smaller than Na+ ions.
K+ ions have a lower charge density than Na+ ions.
a selectivity filter removes the water molecules from K+ ions but not from Na+ ions.
K+ ions are more concentrated inside the cell than outside the cell.
a
46
The flow of which ion makes the largest contribution to the resting potential?
Question 26 options:
K+
Na+
H+
Ca2+
a
47
What would be the resting potential across an artificial membrane if all charged molecules on both sides were equally permeable?
Question 25 options:
–60 mV
+60 mV
0 mV
–1 mV
a
48
The Nernst equation allows one to calculate the
Question 24 options:
resting membrane potential.
equilibrium potential for each ion.
membrane potential when all channels are closed.
membrane potential when all channels are open.
a
49
The resting potential of a typical eukaryotic cell is _______ mV.
Question 23 options:
0
–60
+60
–100
a
50
Channels that open in response to neurotransmitters or other signal molecules are called _______ channels.
Question 22 options:
voltage-gated
ligand-gated
signal-gated
ion
a
51
In a typical mammalian cell, the concentration of _______ is higher on the inside, and the concentration of _______ is higher on the outside.
Question 21 options:
Na+ and Cl–; K+
Na+; K+ and Cl–
K+; Na+ and Cl–
K+ and Cl–; Na+
a
52
Which of the following has the fastest rate of transport?
Question 20 options:
Channel-mediated diffusion
Facilitated diffusion
Active transport
All of the above are equally fast.
a
53
The MDR ABC transporter functions in a number of animal cells to transport
Question 19 options:
glucose into cells.
ions into cells.
poisons and drugs out of cells.
amino acids across epithelia.
a
54
The glucose facilitated diffusion transporter can transport glucose
Question 18 options:
into the cell only.
out of the cell only.
into or out of the cell.
only in the presence of ATP.
a
55
Facilitated diffusion differs from passive diffusion in that facilitated diffusion is
Question 17 options:
mediated only by a protein channel.
mediated only by a protein carrier.
mediated by a protein carrier or channel.
against the concentration gradient
a
56
Molecules that diffuse passively across the plasma membrane most rapidly are
Question 16 options:
small.
hydrophobic.
small and hydrophobic.
small and hydrophilic
a
57
What is the role of tight junctions in the transport of glucose across the intestinal epithelium?
Question 15 options:
They open and allow glucose to pass between the epithelial cells.
They keep the Na+-K+ pumps in the apical membrane only.
They keep the Na+-glucose cotransporter in the apical membrane and the glucose-facilitated transporter in the basolateral membrane.
They keep the glucose-facilitated transporter in the apical membrane and the Na+-glucose cotransporter in the basolateral membrane.
a
58
If a suspension of cells is frozen and fractured, the most likely path of the fracture plane will be
Question 14 options:
between the cell surface and the outside solution.
between the membrane and the cytoplasm of the cells.
through the middle of the cytoplasm.
between the two leaflets of the cell membranes.
a
59
Clusters of sphingolipids, cholesterol, and membrane proteins that move together laterally in the plane of the plasma membrane are called lipid
Question 13 options:
boats.
barrels.
rafts.
barges.
a
60
A major feature included in the updated fluid mosaic model is the
Question 12 options:
interaction of transmembrane proteins with the cytoskeleton.
restriction of glycolipids to the extracellular face of the plasma membrane.
presence of multiple pass transmembrane proteins.
presence of N-linked oligosaccharide side chains on glycoproteins at the cell surface.
a
61
Above the temperature at which lipids are fluid, membrane proteins are able to move
Question 11 options:
from inner to outer surfaces of a membrane.
laterally in the plane of a membrane.
from apical to basal surfaces of intestinal epithelial cells.
only if attached to microtubules or microfilaments.
a
62
Which of the following features of a membrane protein is never used as a membrane anchor?
Question 10 options:
C-terminal glycosylphosphatidyl inositol (GPI)
An N-terminal myristoyl group
Prenyl and palymitoyl group additions
Oligosaccharide side chains
a
63
Clusters of _______ in membrane proteins such as band 3 of the erythrocyte can define hydrophilic segments through which ions (for example, bicarbonate and chloride) can be transported.
Question 9 options:
oligosaccharide side chains
lipid modifications
transmembrane α helices
phosphorylation motifs
a
64
The two erythrocyte proteins glycophorin and band 3 are examples of
Question 8 options:
peripheral proteins.
transmembrane proteins.
cytoskeletal proteins.
β-barrel proteins.
a
65
```
Mammalian erythrocytes (red blood cells) are particularly useful for studies of the plasma membrane because
Question 7 options:
```
they have few peripheral proteins.
they have only one membrane, the plasma membrane.
their plasma membrane is not associated with a cytoskeleton.
their plasma membrane contains no cholesterol.
a
66
Plasma membrane glycolipids are found
Question 6 options:
exclusively in the inner leaflet.
exclusively in the outer leaflet.
equally distributed between the inner and outer leaflets.
only on the basal surface of epithelia.
a
67
Cholesterol is present in the membranes of all
Question 5 options:
cells.
eukaryotic cells.
animal cells.
plant cells
a
68
Plasma membrane phospholipids are
Question 4 options:
located mostly in the outer leaflet of the bilayer.
located mostly in the inner leaflet of the bilayer.
symmetrically distributed between the two membrane halves.
asymmetrically distributed between the two membrane halves
a
69
Gorter and Grendel's classic experiment allowed them to observe that the erythrocyte plasma membrane contains _______ the surface area of the erythrocytes.
Question 3 options:
enough lipid to occupy a monolayer equal to
enough lipid to occupy a monolayer equal to twice
less lipid than would occupy a monolayer equal to
enough lipid to occupy a monolayer equal to one-half
a
70
The plasma membrane's barrier to passive diffusion is primarily a function of the membrane's
Question 2 options:
phospholipids.
cholesterol.
proteins.
glycoproteins.
a
71
The plasma membrane functions as a
Question 1 options:
selective barrier to the passage of molecules.
site for the uptake of macromolecules into the cell.
site for cell–cell interactions.
All of the above
a
72
What is the primary reason that mammalian red blood cells are used in the study of the plasma membrane?
Question 1 options:
There are a lot of them and they are easily obtained.
They contain larger plasma membranes than any other cell type.
They are of particular interest because they are made up of a lipid monolayer.
They lack nuclei and membrane-bounded organelles.
a
73
Two examples of membrane lipids that are present in small amounts are
Question 2 options:
cholesterol and phosphatidylcholine.
glycolipids and phosphatidylinositol.
phosphatidylcholine and sphingomyelin.
phosphatidylethanolamine and phosphatidylserine.
a
74
Which of the following will not solubilize a typical peripheral membrane protein?
Question 3 options:
Detergent
Extreme pH
High salt concentration
Mildly hypertonic saline
a
75
A feature common to most transmembrane proteins is a(n)
Question 4 options:
phosphorylated exterior domain.
α-helical region of about 20 to 25 hydrophobic amino acids.
amino acid sequence rich in acidic residues.
structure consisting almost exclusively of β-sheets.
a
76
Which of the following are integral membrane proteins that do not contain a transmembrane α helix?
Question 5 options:
Band 3
Glycophorins
Glycosylphosphatidylinositol (GPI)-anchored proteins
Spectrins
a
77
Membrane proteins are able to move
Question 6 options:
from the inner to the outer surface of a membrane.
laterally within the plane of a membrane.
from apical to basal surfaces of intestinal epithelial cells.
only if attached to microtubules or microfilaments.
a
78
Which of the following lipids are distinctly enriched in lipid rafts?
Question 7 options:
Cholesterol and sphingolipids
Glycolipids and phosphatidylinositol
Phosphatidylcholine and sphingomyelin
Phosphatidylethanolamine and phosphatidylserine
a
79
Which statement about the glucose transporter is false?
Question 8 options:
It transports glucose across the plasma membrane via a mechanism called facilitated diffusion.
It has 12 α-helical transmembrane segments.
A conformational change in the transporter is involved in the transport process.
Flow through it is unidirectional
a
80
Which statement about ion channels is true?
Question 9 options:
They are opened either by the binding of ligands or by changes in electric potential across the membrane.
They require ATP.
They are open most of the time.
The rate of transport is slow compared to the rate of transport via carrier proteins.
a
81
The resting plasma membrane potential as described by the Nernst equation is the sum of the movement of many ions. However, in practice, the movement of _______, a single ion, is the major component determining membrane potential.
Question 10 options:
Ca2+
Cl–
K+
Na+
a
82
Which statement about the relative concentrations of Na+ and K+ inside and outside of a typical mammalian cell is true?
Question 11 options:
The concentration of Na+ and K+ outside the cell is about 30 times higher than inside the cell.
The concentration of Na+ outside the cell is about 30 times higher than inside the cell, and the concentration of K+ inside the cell is 10 to 30 times higher than outside the cell.
The concentration is the same for both ions, but there is a Cl– ion concentration gradient across the plasma membrane.
The concentration of Na+ inside the cell is 30 times higher than outside the cell, and the concentration of K+ outside the cell is 10 times higher than inside the cell.
a
83
Although Na+ is smaller than K+, its passage through the K+ channel is blocked by the _______ filter.
Question 12 options:
CO2
negativity
positivity
selectivity
a
84
Transport of glucose into the intestinal epithelium is driven by ion gradients established by the
Question 13 options:
ATP pump.
H+ pump.
Na+-K+ pump.
K+ channel
a
85
Active transport differs from facilitated diffusion in that
Question 14 options:
ions are not transported via active transport, only by facilitated diffusion.
active transport requires a protein component, whereas facilitated diffusion occurs by simple diffusion through the plasma membrane.
active transport involves the transport of molecules up their concentration gradient.
active transport involves a conformational change in the transport molecule.
a
86
Which statement about ABC transporters is false?
Question 15 options:
Each family member has an ATP-binding cassette.
Each member of the family is a Cl– channel.
They are the largest family of membrane transporters in humans.
Each member of the family has shared domain structure features.
a
87
The ingestion of large particles by cells is a form of endocytosis known as
Question 16 options:
fluid phase endocytosis.
macropinocytosis.
phagocytosis.
transcytosis.
a
88
Which of the following is not involved in receptor-mediated endocytosis?
Question 17 options:
Clathrin
Adaptor proteins
Internalization signals
Pseudopodia
a
89
LDL uptake by cells is one of the functions of
Question 18 options:
receptor-mediated endocytosis.
phagocytosis.
caveolae.
ABC transporters.
a
90
Mutations in the internalization signal of endocytic receptors prevent their interaction with
Question 19 options:
adaptor proteins.
caveolin.
clathrin.
dynamin.
a
91
The pH of endosomes and lysosomes is
Question 20 options:
acidic.
alkaline.
neutral.
unknown.
a
92
In their acceptance speech for the Nobel Prize in 1985, Michael Brown and Joseph Goldstein said, "Cholesterol is a Janus-faced molecule. The very property that makes it useful in cell membranes, namely its absolute insolubility in water, also makes it lethal." Explain this remark.
a
93
Detergents are used to solubilize membranes because they are dual molecules possessing both hydrophobic and hydrophilic portions. Why are they also used as cleaning reagents (to clean, for example, clothes and dishes)?
a
94
According to the generally accepted fluid mosaic model of membrane structure, membranes are two-dimensional fluids through which proteins can move freely in lateral directions. Provide an example of a membrane protein that is not free to move laterally within a plasma membrane.
a
95
How does water enter a cell from the extracellular space?
a
96
Why are most ion channels gated?
a
97
How does the plasma membrane come to be hyperpolarized locally during action potential reversal?
Question 26 options:
a
98
The drug ouabain inhibits the plasma membrane Na+-K+ pump. Why does it also inhibit glucose transport across the intestinal epithelial layer?
a
99
Cystic fibrosis (CF) is the most common inherited disease of Caucasians. It is due to mutations in an ABC transporter, the cystic fibrosis transmembrane conductance regulator (CFTR), which is a Cl– and bicarbonate channel. Why have efforts at gene therapy to correct CF concentrated on the lungs when CF affects other tissues as well?
a
100
Shibere is a temperature-sensitive mutant in the protein dynamin in the fruit fly Drosophila. Why do flies fall out of the air when shifted to the nonpermissive temperature?
a
101
Why does incubation of cells with NH3 cause the selective osmotic swelling of endosomes and lysosomes and not of other organelles in the cell?
Question 30 options:
a
102
Why is dissociation of ligands from their receptors in endosomes an important feature of receptor-mediated endocytosis?
a
