AAAAAAAA Flashcards
(239 cards)
1
Q
conversion of an impulse or stimulus from one physical or chemical form to another. Also is the process by which a cell responds to an extracellular signal
A
Signal transduction
2
Q
Communication between cells involves four essential elemnts
A
- signaling cell
- signaling molecule
- Target cell
- Receptor molecule
3
Q
In intracellular communication signal is recieved by _______. It uses ________ messengers
A
receptors; second
4
Q
a. Proteins or peptides
b. Amino acids or nucleotides
c. Steroids and fatty acid derivatives
d. Dissolved gases
Are all examples of what?
A
extracellular signal molecules
5
Q
What are the 3 modes of signaling and the 1 mode of long distance signaling?
A
Short term:
(NPC) Neuronal, paracrine, contact-dependant;
Long term:
Endocrine
6
Q
Endocrine signaling is _____ term and its signaling molecules are called _______. These are produced in endocrine glands.
A
long; hormones
7
Q
pancreas produces insulin which regulates glucose uptake. This is an example of what type of signaling?
A
Endocrine
8
Q
A type of local signaling. Signaling molecules released by one cell into the extracellular fluid act as local mediators. Signals act on neighboring target cells.
A
Paracrine Signaling
9
Q
These are examples of what kind of signaling?
Growth factors – regulate growth and proliferation
Cytokines - molecules that regulate inflammation
A
Paracrine signaling
10
Q
Type of Local signaling. Cells respond to signaling molecules that they themselves produce.
Example: Cancer cells
A
Autocrine signaling
11
Q
Type of Local Signaling. Neuronal signals are transmitted electrically along a nerve cell axon.
Results in the release of neurotransmitters onto adjacent target cells. Message delivered quickly and specifically
A
Neuronal signaling
12
Q
Involves direct contact between neighboring cells.
Cell-surface-bound signal molecule binds to a receptor protein on an adjacent cell.
A
Contact-Dependent Signaling
13
Q
Insulin, Acetocholyine, EGF, and Delta are all examples of what?
A
signal molecules.
14
Q
______ may be located on the cell surface or inside the cell.
A
receptors
15
Q
_________ receptors bind extracellular signal molecules
A
Cell-surface receptors
16
Q
Most Extracellular Signal Molecules are ______ and _____.
A
large; hydrophilic
17
Q
These receptors are located in in the cytosol or in the nucleus. They respond to small hydrophobic signal molecules that can diffuse across the plasma membrane
A
Intracellular receptors
18
Q
Steroid hormones are examples of small hydrophobic signal molecules that would bind to _______ receptors to regulate gene transcription or other functions
A
intracellular
19
Q
Cells of multicellular organism encounter hundreds of different signaling molecules, but cells must respond to correct signal. The responding cell must express specific ________
A
receptor
20
Q
T/F: A cell’s response to a signal can be fast or slow
A
true
21
Q
In this type of cell response/signal, the signal affects the activity of protein already present inside the cell
Example: contraction of muscle cells
A
Fast signals
22
Q
In this type of cell response/signal, the response requires changes in gene expression and production of new proteins
Examples: cell growth, cell division
A
Slow signals
23
Q
Cell-surface ________ relay extracellular signals via intracellular signaling pathways.
Intracellular signaling molecules interact with specific ______ proteins. These change the behavior of the target cell
A
receptors; effector
24
Q
T/F: Effector proteins change the behavior of the target cell
A
true
25
_______________:
-Relay signal
-Amplify signal
-Integrate signal: Detect signal from more than one signaling pathway
Distribute signal
Modulate signal via feedback
Intracellular signaling proteins
26
T/F: Feedback only occurs in specific parts of the signaling pathway
false, Feedback can occur anywhere along signaling pathway
27
Feedback can be _______ or _______
positive; negative
28
Molecular switches are ______ proteins. The receipt of signal causes them to toggle between ______ and _______ state.
effector; active; inactive
29
There are different classes of Molecular Switches.
Switches regulated by __________, such as protein ____________ and protein _______.
Phosphorylation; protein kinases; protein phosphates
30
Phosphorylation Cascade
Many switch proteins are themselves kinases.
yea
31
Molecular switches:
____________: activate when bound to GTP. It switches itself off by hydrolyzing its bound GTP to GDP
GTP-binding protein
32
Types of GTP-binding proteins:
_________proteins- relay messages from G-proteins coupled receptors.
________________- their activity is controlled by two types of regulatory proteins
Trimeric GTP-binding proteins; Monomeric GTPases.
33
The activity of Monomeric GTPases is controlled by two types of regulatory proteins: _____ & ______
GEF; GAP
34
T/F: GEF switches the protein off and GAP switches the protein on
false GEF on, GAP off
35
Cell-surface receptors fall into three main classes
_________ receptors
_________ receptors
_________receptors
Ion-channel-coupled; G-protein-coupled; enzyme-coupled
36
This type of receptor changes the permeability of the membrane to a specific ion and leads to change in membrane potential
Ion-channel-coupled receptors
37
This type of receptor activates membrane-bound G-protein. G-proteins like trimeric proteins initiate intracellular signaling cascade (activate or inhibit enzyme or ion channel in the plasma membrane)
G-protein-coupled receptors
38
These receptors act as enzymes to activate intracellular signaling pathways. They associate with enzymes that activate intracellular signaling pathways.
Enzyme-coupled receptors
39
T/F: Same extracellular signaling molecule can act on more than one type of receptor
true
40
These receptors are responsible for rapid transmission of signal across synapse. They convert chemical signals (neurotransmitter) into electrical signals (change in membrane potential).
Ion-channel-coupled receptors
41
T/F: G-protein-coupled receptors (GPCR) are the largest family of cell surface receptors
true
42
GPCRs associate with intracellular _____________. They mediate response to diverse extracellular signals
trimeric G proteins
43
GPCR Structure:
______(single/double) polypeptide chain
Is embedded in membrane
Has seven transmembrane ________
Single; alpha helices
44
Ligand binding causes what change in GPCR? And activates what?
causes conformational change in GPCR
Leads to activation of G protein
45
T/F: Several varieties of G-proteins share similar structure & mode of operation
true
46
In G-protein subunits the alpha and y subunits are tethered to membrane by _______.
However, the alpha subunit binds GDP/GTP.
GDP bound is ______
GTP bound is ______
lipid tail; inactive; active
47
Stimulation of GPCRs activates G-protein subunits.
-Conformational change of GPRC leads to conformation change of __________
g protein
48
Alpha subunit exchanges GDP for ____
- _____ required
- GTP binding leads to more conformational changes
GTP; GEF
49
Diverse signal molecules activate ______
- Proteins
- Small peptides
- Derivatives of amino acids
- Derivatives of fatty acids
GPCR
50
G protein activity:
An activated ________ interacts with its target protein. Target protein is activated (in this example). α subunit hydrolyzes bound GTP to GDP.
Activated *By* complex interacts with its target protein and inactive subunits reassemble.
α subunit
51
Some bacterial toxins cause disease by altering the activity of G Proteins
Examples are: _________toxin & _______ toxin.
Cholera ; Pertussis
52
T/F: Some G proteins directly regulate ion channels
true
53
Some G proteins directly regulate ion channels. Opening of ions channels causes immediate effect.
Example: heart pacemaker cells
Acetylcholine binds to GPCR which leads to activation of the G protein, G1. The activated βγ complex directly opens a K+ channel.
RESULT
Increased membrane permeability to ____ .
Also, makes membrane harder to activate and slows the heart rate
K+;
54
Many G proteins activate _____________.
Less rapid and more complex consequences.
Membrane-bound enzymes produce ____________ (aka
second messengers) which spread throughout a cell by diffusion. They then bind to specific signaling proteins in the cell and influence their activity.
membrane-bound enzymes; small messenger molecules
55
T/F: Cyclic AMP (cAMP) and Calcium ions are small messenger molecules
true
56
________:
Its an enzyme in the plasma membrane
One of the most frequent enzyme target for G proteins
Converts ATP to cAMP
Adenylyl cyclase
57
__________:
It converts cAMP to AMP
This terminates the cAMP signal
cAMP phosphodiesterase
58
cAMP usually activates AMP-dependent protein kinase (PKA).
cAMP binds to regulatory subunit of PKA releasing catalytic subunit.
Catalytic subunit of ______ phosphorylates various other proteins
PKA
59
In response to an extracellular signal, cAMP rises rapidly.
true
60
T/F: Epinephrin (aka adrenaline) binds to the GPCR adrenergic receptor.
true
61
Epinephrine stimulates _________ breakdown in skeletal muscle cells.
Increase in cyclic AMP activates ______
PKA phosphorylates and activates an enzyme called _________________
Phosphorylase kinase activates glycogen phosphorylase, the enzyme that breaks down glycogen.
glycogen; PKA; phosphorylase kinase
62
A rise in intracellular cyclic AMP can activate __________.
Activated PKA can enter the nucleus and phosphorylate specific transcription regulators
gene transcription
63
______________:
It's one of the most frequent enzyme target for G proteins
Membrane bound enzyme.
Cleaves phospholipid – inositol phospholipoid
Generates second messengers IP3 and DAG
Phospholipase C
64
Phospholipase C cleaves a phospholipid called_____________.
And generates second messengers ____ and ____
inositol phospholipoid; IP3; DAG
65
The "hat" on the Inositol Phospholipid is what?
the sugar inositol
66
Inositol phospholipid pathway triggers a rise in intracellular _______-
Ca2+
67
DAG in the membrane recruits protein kinase C (PKC).
PKC is activated by _____. PKC activates intracellular proteins.
Ca2;
68
The cell maintains _______(high/low) cytosolic levels of Ca2+.
A _________(increase/decrease) in cytosolic Ca2+ signal triggers many biological processes.
low; increase
69
T/F: Fertilization of an egg by a sperm triggers an decrease in cytosolic Ca2+ in the egg
false, increase
70
Effects of Ca2+ mostly indirect through Ca2+-responsive proteins such as __________ which changes shape once Ca2+ binds.
Calmodulin
71
CaM-kinases are activated by _________. They phosphorylate select proteins
calmodulin
72
A GPCR signaling pathway generates a ____________.
The dissolved gas carries a signal to adjacent cells
Amino acid arginine broken down into NO
NO activates an enzyme guanylyl cyclase
Cyclic GMP (second messenger)
dissolved gas
73
This is the largest class of enzyme-coupled receptors. The cytoplasmic domain functions as a tyrosine kinase after activation. Full activation requires: Ligand binding & Autophosphorylation
Receptor Tyrosine Kinases (RTKs)
74
RTKs Activatio:n
Binding of signal molecule leads to dimerization of RTK.
Dimerization leads to _______________on specific tyrosine residues
auto-phosphorylation
75
Recruitment of intracellular signaling complex
Phosphorylated tail serves as________.
docking site;
76
_____ domains allow proteins containing those domains to dock to phosphorylated tyrosine residues on other proteins
SH2
77
Activation of an _____ stimulates the assembly of an intracellular signaling complex
RTK
78
Terminating the signaling cascade:
Protein Tyrosine phosphatases (PTPs) will ____________ RTK and intracellular signaling proteins. Then Receptor endocytosis (Degradation, Recycling) occurs.
dephosphorylate; endocytosis
79
Most RTKs activate the monomeric GTPase _____
adaptor recruits a Ras guanine nucleotide exchange factor (Ras‑GEF). Activated Ras can activate a MAP-kinase.
Ras;
80
Ras activates a _______ signaling module. Which is a three-kinase signaling module. Final kinase MAP kinase
activates various effector proteins.
MAP-kinase
81
RTKs recruit and activate phosphoinositide 3-kinase (PI 3-Kinase) . PI 3-kinase _________ an inositol phospholipid to produce lipid docking sites in the plasma membrane
phosphorylates
82
Inositol phospholipid attracts intracellular signaling proteins.
______ is a protein kinase that is activated at the membrane by two other protein kinases. It's
released from the plasma membrane after phosphorylation and phosphorylates various downstream proteins on specific S/T residues.
Akt (PKB)
83
Activated Akt promotes __________
AKT phosphorylates and inactivates ______.
Bad promotes apoptosis by binding to and inhibiting Bcl2. Phosphorylated Bad releases Bcl2 and
Bcl2 blocks apoptosis and promotes cell survival.
cell survival; Bad
84
Akt stimulates cells to grow in size by activating the S/T kinase ______.
Tor
85
Akt stimulates cells to grow in size by activating the S/T kinase Tor. Akt acts on a Tor inhibitor (turns inhibitor off). Activated Tor stimulates ___________ and inhibits protein degradation.
protein synthesis
86
Some receptors activate a fast track to the nucleus.
Example: Notch Signaling (contact dependant)
nerve-cell production in the fruit fly Drosophila. Delta is the signaling molecule and Notch is the receptor.
Contact
87
T/F: Delta is the signaling molecule and Notch is the receptor.
true
88
After Delta (signal molecule ) binds to Notch (receptor) a protease cleaves tail of Notch. The Notch tail then migrates to nuclease and _____ Notch-responsive genes.
activates
89
Intracellular receptor proteins are found in the _________ or ________ of target cells
cytoplasm; nucleus
90
Protein kinase networks: ______ information and
Control complex cell behaviors
Integrate
91
Can GTP-binding proteins act as molecular switches,
letting a cell know that a signal has been received?
yes
92
What determines the direction that cellulose microfibrils are laid down in the extracellular space of a plant cell?
orientation of microtubules on the cytoplasmic side of the plasma membrane
93
What feature of glycosaminoglycans (GAGs) allows the extracellular matrix in cartilage to resist compression?
The negative charges on GAGs attract sodium ions, which draw water into the extracellular matrix to
form a water-filled gel.
94
Which statement is true about stem cells?
A. They can divide for the lifetime of the organism.
B. They are terminally differentiated.
C. They are usually present in large numbers, especially in tissues that undergo rapid renewal.
D. They always divide asymmetrically, giving rise to two different daughter cells.
A. They can divide for the lifetime of the organism.
95
Which is true of induced pluripotent stem (iPS) cells?
A. They can be used to produce whole organs for transplantation.
B. They can be produced artificially using a single transcription regulator.
C. They behave like embryonic stem cells.
D. They are produced by nuclear transplantation.
E. They can be produced by incubating adult fibroblasts with Ca2+.
They behave like embryonic stem cells.
96
In most cases, how many mutations are required for a normal cell to turn into a cancer cell?
more than three
97
Which statement is true about human cells?
A. Cancer cells maintain their telomeres by reactivating the enzyme telomerase.
B. Cancer cells lose the ability to produce the enzyme telomerase.
C. Cancer cells tend to lack telomeres.
D. Unlike normal cells, cancer cells can only divide a limited number of times in culture.
E. In cancer cells, telomeres grow progressively shorter with each cell division.
Cancer cells maintain their telomeres by reactivating the enzyme telomerase.
98
Which type of mutation would not typically convert a proto-oncogene into an oncogene?
A. chromosomal deletion of the region containing the proto-oncogene
B. chromosomal rearrangement that leads to overproduction of the normal proto-oncogene protein
C. gene amplification
D. mutation in the coding sequence that leads to the production of a hyperactive protein
E. chromosomal rearrangement that leads to the production of a hyperactive protein
chromosomal deletion of the region containing the proto-oncogene
99
A small dye molecule injected into a plant cell can pass into adjacent plant cells because of the presence of...
plasmodesmata!
100
Which is the name of a specialized cell junction that allows rapid spread of electric current via the flow of ions between animal cells?
Gap junction
101
In animal cell junctions, _______ seal intercellular spaces, _______ reinforce attachments, and _______ allow for communication between cells.
tight junctions;
desmosomes;
gap junctions
102
Connexons are channel structures that make up...
gap junctions.
103
Which of the following junctions is most abundant in tissues such as skin that are required to resist significant mechanical stress?
A. gap junctions
B. desmosomes
C. focal adhesions
D. tight junctions
E. All are abundant in tissues resisting stress.
desmosomes
104
The type of adhesive junction that connects epithelial cells to the basal lamina is a...
hemidesmosome.
105
Proteoglycans in the extracellular matrix of animal tissues...
allow cartilage to resist compression.
106
A basal lamina is...
a thin layer of extracellular matrix underlying an epithelium.
107
Adherens junctions...
A. can be used to bend epithelial
sheets into tubes.
B. are most often found at the basal surface of cells.
C. are found only in adult tissues.
D. involve fibronectin and integrin interactions.
can be used to bend epithelial sheets into tubes.
108
Cells that are terminally differentiated...
can no longer undergo cell division.
109
When a terminally differentiated cell in an adult body dies, it can typically be replaced in the body by a stock of
proliferating precursor cells.
110
Induced pluripotent stem (iPS) cells...
can be created by the expression of a set of key genes in most somatic cell types, including cells derived from adult tissues.
111
A metastasis is...
a secondary tumor in a different part of the body that arises from a cell from the primary tumor.
112
Which of the following statements about tumor suppressor genes is FALSE?
A. Gene amplification of a tumor suppressor gene is less dangerous than gene amplification of a proto-
oncogene.
B. Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal
cells.
C. Inactivation of tumor suppressor genes leads to enhanced cell survival and proliferation.
D. Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than
individuals with two functional copies of a tumor suppressor gene.
Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal
cells.
113
Ras is a GTP-binding protein that is often defective in cancer cells. A common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. From this description, the [NORMAL] Ras gene is a...
proto-oncogene.
114
A set of cells in the intestinal epithelium divides continually in order to replace dead cells. A microscopic examination of this population of cells would show that most of them...
are in interphase.
115
T/F: The cytoskeleton is flexible and dynamic
true
116
Which phase of the cell cycle is not part of interphase?
A. S
B. G0
C. G1
D. G2
E. M
M
117
How does a nucleus in G2 differ from a nucleus in G1?
The G2 nucleus has double the amount of DNA as the G1 nucleus.
118
Which of the following statements is false?
A. Activated S-Cdk initiates DNA replication.
B. Activated G1-Cdks and G1/S-Cdks help drive cells through G1 into S phase.
C. Activated M-Cdk triggers the onset of cytokinesis.
Activated M-Cdk triggers the onset of cytokinesis.
119
Which of the following occurs at specific times in the cell cycle?
A. Some cyclins are ubiquitylated and degraded in proteasomes.
B. Some cyclins are methylated and degraded in proteasomes.
C. Some Cdks are ubiquitylated and degraded in proteasomes.
D. Some Cdks are phosphorylated and degraded in proteasomes
Some cyclins are ubiquitylated and degraded in proteasomes.
120
What is true about the phosphorylation of condensins by M-Cdk?
It triggers their assembly onto DNA, compressing chromosomes into a more compact form.
121
Which extracellular signal proteins trigger a wave of G1/S-Cdk activity?
mitogens
122
Which of the following statements is false?
A. Cyclins help activate Cdks by phosphorylating them.
B. Cyclins vary in concentration at different stages of the cell cycle.
C. Cyclins are degraded at specific times in the cell cycle.
D. Cyclins have no enzymatic activity on their own.
Cyclins help activate Cdks by phosphorylating them
123
Most of the diversity in the rates of cell division in the adult body lies in variations in the time that each cell spends in which phase(s)?
G1 phase and G0 phase
124
Why does the activation of M-Cdk begin abruptly?
Each M-Cdk complex can activate more M-Cdk.
125
Chromosomes line up at the spindle equator during which phase of the cell-division cycle?
metaphase
126
The anaphase-promoting complex or cyclosome (APC/C) triggers the onset of anaphase by doing which of the following?
triggering the destruction of the cohesins that hold the sister chromatids together
127
Which of the following statements is true?
A. Many cells die by necrosis in many normal, adult human tissues.
B. Many cells die by necrosis during normal animal development.
C. Many cells die by apoptosis in many normal, adult human tissues.
Many cells die by apoptosis in many normal, adult human tissues.
128
Which situation would be the most likely result of a mutation in a eukaryotic organism that causes it to produce less p21 protein than normal?
Cells with radiation-induced DNA damage would continue through the cell cycle without repairing
the damaged DNA.
129
An environmental change that leads to the production of less than the expected amount of cyclin would tend to _______ the activity of the Cdk. This would lead to _______ phosphorylation of the target protein, which in turn
would lead to _______ cells being stopped at the checkpoint.
decrease; decreased; more
130
At the milestone that defines [anaphase], the chromosomes...
Separate
131
The structures that line up the chromatids on the equatorial plate during metaphase are called
polar and kinetochore microtubules.
132
The microtubules of the mitotic spindle attach to a specialized structure in the centromere region of each chromosome called the
kinetochore
133
At the milestone that defines [metaphase], the chromosomes...
line up at the equatorial plate.
134
In mitotic metaphase, a cell with eight sister chromatids has _______ centromere(s).
Four
135
At the milestone that defines [telophase], the chromosomes...
are at opposite poles.
136
Chromosomes decondense into diffuse chromatin
A. at the end of telophase.
B. at the beginning of prophase.
C. at the end of interphase.
D. at the end of metaphase.
at the end of telophase.
137
The event in the cell division process that clearly involves actin microfilaments is...
cytokinesis in animal cells.
138
In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated?
at the end of G2
139
Which of the following statements about the cell cycle is FALSE?
A. Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic
cells.
B. An unfavorable environment can cause cells to arrest in G1.
C. A cell has more DNA during G2 than it did in G1.
D. The cleavage divisions that occur in an early embryo have short G1 and G2 phases.
Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic
cells.
140
The concentration of mitotic cyclin
(M cyclin)
falls toward the end of M phase as a result of ubiquitylation and degradation.
141
Which of the following statements is FALSE?
A. Cdc25 dephosphorylation of Wee1 activates the kinase, promoting the G2/M transition.
B. Phosphorylation of mitotic Cdk by the inhibitory kinase (Wee1) makes the Cdk inactive.
C. Inhibiting the Cdc25 phosphatase will delay the G2/M transition.
D. The activating phosphatase (Cdc25) removes the phosphates from mitotic Cdk that were added by Wee1, so that M-Cdk will be active.
Cdc25 dephosphorylation of Wee1 activates the kinase, promoting the G2/M transition.
142
The G1 DNA damage checkpoint...
involves the inhibition of cyclin–Cdk complexes by p21.
143
Condensins
assemble into complexes on the DNA when phosphorylated by M-Cdk.
144
At the end of DNA replication, the sister chromatids are held together by the
cohesins.
145
Sister chromatid separation occurs because __________ are destroyed by the APC/C.
securins
146
Programmed cell death occurs
by means of an intracellular suicide program.
147
Apoptosis differs from necrosis in that necrosis
causes cells to swell and burst, whereas apoptotic cells shrink and condense.
148
The overall shape of an animal cell is determined by its
cytoskeleton
149
The cytoskeleton is composed of three major components, each with distinct functions. Which represents the correct order of these components, from smallest to largest size?
Microfilaments, intermediate filaments, microtubules
150
Which of the following is not a function of the cytoskeleton?
passive transport
151
Researchers observe that while the actin microfilaments in an amoeba seem to be intact, the organism appears incapable of forming pseudopods for movement. They conclude that its immobility may be caused by the absence of the protein
myosin.
152
Microtubules are made of...
tubulin, and they are essential in chromosome movement during mitosis.
153
What type of agent would be most likely to disrupt the structures of microvilli?
Actin depolymerizing agent
154
A cancer drug is being tested, and it is found that although the cancer cells can divide, the nuclear envelope cannot re-form. It is determined that a protein substance is sequestered so that it cannot be polymerized into
the necessary structure. What is the most likely protein target of the drug?
Lamin
155
A patient is admitted to the hospital for dehydration and malnutrition. On close observation of the intestine, it appears that the cells lining the intestine have fully formed microvilli. However, these microvilli are not uniformly standing upright and protruding into the lumen of the intestine, but are lying down so that full exposure to the contents of the intestine cannot be obtained. The doctors conclude that the patient may have a defect in what cellular component?
Actin
156
A cultured cell line appears to be having trouble surviving. Upon closer examination, you find that the cells do not appear to have normal chromosome separation. Based on this observation, you decide to check for the presence of a mutated protein. You will be sure to analyze the gene for which protein?
Tubulin
157
At a cellular level, what is the mechanism behind rigor mortis?
After death, ATP production ceases and ATP is needed for myosin release from actin.
158
The _______ is a cell structure with an internal cross section showing a characteristic “9 + 2” morphology.
cilium
159
Microfilaments function in
a. muscle contraction.
b. cytoplasmic streaming.
c. cell division.
d. maintenance of animal cell shape.
(All of these)
160
Tubulin may assemble onto one end while disassembling from the other end of the same microtubule simultaneously in a process known a
treadmilling.
161
Dynamic assembly and disassembly of a cytoplasmic microtubule in a cell occurs primarily at its plus end,
because its minus end is usually anchored to
a microtubule organizing center.
162
Mutations of keratins in the ________ that resist tensile forces in the skin cause the blistering disease known as
epidermolysis bullosa simplex.
intermediate filaments
163
Actin bundles give shape and support to ________ found in intestinal mucosal cells.
microvilli
164
Activation of which of the following is associated with the formation of focal adhesions and stress fibers?
Rho
165
Each monomer of actin binds one molecule of the nucleotide triphosphate
ATP
166
Actin exists in cells in two major forms called
G actin and F actin.
167
ATP is hydrolyzed by actin...
after assembly but before disassembly.
168
Branching of actin filaments can be initiated by
Arp2/3.
169
Actin filaments are bound into bundles of parallel filaments by the proteins...
(alpha symbol)-actinin and fimbrin.
170
Which of the following movements is NOT based on actin–myosin interactions?
a. Cell migration (crawling) over surfaces
b. Chromosome movement during anaphase A
c. Cytokinesis of animal cells
d. Phagocytosis
Chromosome movement during anaphase A
171
Myosin _______ is present in muscle sarcomeres
II
172
Microtubules are assembled from...
dimers of (alpha)- and (beta)-tubulin.
173
The GTP bound to (beta)-tubulin hydrolyzes to GDP and Pi
following polymerization but before depolymerization.
174
The major microtubule-organizing center in most animal cells is the...
centrosome.
175
At the end of interphase, the part of the microtubule farthest from the centrosome is the _______ end.
plus
176
Rings of the protein _______ in the pericentriolar material nucleate microtubule assembly.
y-tubulin
177
Microtubules are not involved in...
cytokinesis
178
The cargo carried by kinesin along microtubules binds to kinesin on which region?
Tail
179
The beating of cilia and flagella occurs by means of _______-based _______.
dynein; microtubule sliding
180
The basal bodies of cilia and flagella are similar in structure to (and can form from)
centrioles.
181
Keratin intermediate filaments are anchored to junctions called
desmosomes.
182
Autocrine signals bind to...
a. receptors on adjacent cells.
b. receptors on neighboring cells.
c. receptors on the cell that produced them.
d. internal receptors located inside cells.
e. receptors on cells far away from the cell that produced them.
receptors on the cell that produced them.
183
Paracrine signals bind to
receptors on neighboring cells.
184
Signals that travel to distant cells through the circulatory system are
Hormones
185
The major difference between a cell that responds to a signal and one that does not is the presence of a
receptor
186
Which statement about cell signaling is false?
a. Cells are bombarded with numerous signals, but they do not respond to all of them.
b. A cell must possess the specific receptor to respond to a particular signal.
c. Chemical signaling molecules have specific binding sites.
d. Receptor specificity in cells allows a response to a specific signal.
e. There are only a few kinds of receptor proteins.
f. does not exist, since the molecule can diffuse across the cell membrane.
There are only a few kinds of receptor proteins.
187
Receptors can be divided into two general classes according to their cellular location: _______ receptors and _______ receptors.
intracellular; membrane
188
A researcher working with mammalian kidney cells grown in culture observed that cells treated with a proteolytic enzyme (an enzyme that breaks down proteins) lost the ability to respond to the hormone vasopressin but not to the hormone aldosterone. Which is a reasonable explanation for this observation?
The vasopressin receptor is embedded in the cell membrane with an external portion that binds its ligand, whereas the aldosterone receptor is an intracellular receptor.
189
Which of the following has its receptors on a gated ion channel for sodium ions (Na+)?
Acetylcholine
190
A benefit of the many steps involved in a protein kinase cascade is that they involve
amplification of the signal being communicated.
191
In a signal transduction pathway involving G protein-coupled receptors, the receptor first binds the ligand and activates a G protein. After the GTP-bound subunit of the G protein separates from the rest of the G protein, it travels until it encounters
an effector protein.
192
When a G protein is activated in a signal transduction pathway,
GDP is released from the G protein, and GTP occupies the nucleotide-binding site.
193
Which statement about ligand‒receptor complexes is false?
a. For most ligand–receptor complexes, binding, as opposed to dissociation, is favored based on chemistry’s law of mass action.
b. Ligand–receptor interactions are reversible.
c. Drugs that prevent binding of receptors’ specific ligands can alter human behavior.
d. After binding to a cell membrane receptor, a ligand participates in the cellular response.
e. A ligand is a chemical signal.
After binding to a cell membrane receptor, a ligand participates in the cellular response.
194
A deer smells a predator as it passes by and quickly bounds to safety. Which sequence represents the correct
order of steps in the signal transduction pathway that is involved?
Signal travels to target cell, receptor binds signal, conformational change occurs in receptor, signal is
transduced within cell, effects from signal transduction occur
195
The hydrolysis of phosphatidyl inositol-bisphosphate (PIP2) results in
inositol trisphosphate and diacylglycerol.
196
Inositol triphosphate (IP3) is released into the cytoplasm when phosphatidyl inositol-bisphosphate (PIP2) is hydrolyzed. IP3 is one type of molecule that can directly....
open Ca2+ channels and increase cytosolic calcium.
197
What is the most stable and least soluble part of the cytoskeleton?
intermediate filaments
198
Intermediate filaments __________(are/are not) found in most animal cells but ________(are/are not) found in plant cells.
are; are not
199
IFs assemble from ______ protein subunits. The monomer consists of an α-helical central rod domain. Which coils with other monomers to form a _________. Dimers line up to form a staggered, antiparallel tetramer
fibrous; coiled-coil dimer
200
T/F: IFs assembly: The ends of a tetramer are different
false, both ends are the same
201
T/F: IFs are tissue type specific
true
202
This is the most diverse class of IFs. It's found in all epithelial tissue.
Anchor to attachment points
--Cell-cell attachments = **desmosomes**
--Cell-substrate = **hemidesmosomes**
It strengthen cells against mechanical stress
Keratin filaments
203
Cell-cell attachments = _________(desmosomes/ hemidesmosomes)
Cell-substrate = _________(desmosomes/ hemidesmosomes)
desmosomes;hemidesmosomes
204
Mutations in ___________ cause ALS
neurofilaments
205
Under the nuclear envelope is a meshwork of Ifs called lamins that supports and strengthens the nuclear envelope
Nuclear lamina
206
T/F: the nuclear lamina never dissasembles
false, it needs to disassemble during cell division
207
IFs are stabilized and reinforced by accessory proteins such as _________ , a linker protein that:
Cross-links IFs into bundles
Connects IFs, microfilaments, and microtubules
Connects IFs to hemidesmosomes
Plectin
208
The site at which microtubule assembly originates.
Acts as anchor of microtubules.
Microtubule organizing centers (MTOC)
209
T/F: Centrosome is an MTOC
true
210
Microtubule have 2 structurally distinct ends:
____ end
____ end
Plus; Minus
211
T/F: Protofilaments lack polarity
false, because of dimer orientation, protofilaments have an inherent polarity
212
Tubulin dimers added to _____ (plus/minus) end more rapidly than ____ (plus/minus) end.
plus;minus
213
Which side at the Microtubule organizing centers (MTOCs) are anchored?
minus ends
214
Centrosome consists of a pair of _______ surrounded by a ______ of various proteins. In the centrosome matric, ____-tubulin is found.
centrioles; matrix; y-tubulin
215
The random cycles of rapid shrinkage (depolymerization) followed by slower growth (polymerization). This process allows MTs to undergo rapid remodeling and to explore the space of the cell by growing into new areas and then shrinking back. What is this called?
Dynamic Instability
216
Dynamic Instability is driven by ______________
GTP-hydrolysis
217
Why does Microtubule Catastrophe (Dramatic shrinkage) takes place?
because the plus end of a microtubule is structurally unstable
218
T/F: Some organelles are tethered to microtubules
true
219
T/F: In nerve cell axons, the microtubules all point in different directions
false, they all point in the same direction (think of axon)
220
Microtubule-associated proteins (SOL)
S________ MTs against disassembly (+–end tubulin interacting proteins)
O________ MTs
L______ MTs to other cell components (plectin)
Stabilize; Organize; Link
221
These serve as molecular motors (kinesin, dynein) and stabilize, organize and link microtubules.
Microtubule-associated proteins
222
Organelle Movement and Vesicle transport requires _____ proteins
motor
223
Motor proteins ______(use/don't use) energy.
They can move in ______(one/more than one) in one direction.
use; one
224
On the Microtubule Motor Proteins:
The Cytoplasmic dynein moves toward the ______ end. And the Kinesin moves toward ______ end.
Tail interacts with cargo, either directly or indirectly through adaptor proteins.
minus; plus
225
What protein along the microtubule looks like its "walking" with 2 globular head domains?
kinesin
226
Cilia and Flagella contain stable __________.
Moved by ______ motor protein
microtubules; dynein
227
Cell crawling depends on _______ actin
cortical
228
Cell crawling involves distinct events:
1) Extension of a protrusion. What is occurring at the growing tip of the protrusion?
2) Attachment to substrate
3) Generation of tension, which pulls the cell forward
4) Detachment
actin polymerization
229
Many nonmuscle cells are capable of crawling over a substrate using ____________ and/or ____________
lamellipodia; filopodia
230
In the extension of the protrusion (during cell crawling) the assembly of microfilaments is driven by what?
ARP
231
ARP complex nucleates new branches on the sides of _________
filaments
232
During the "Attachment to Substrate" step of cell crawling, whats being formed at the front of the cell?
new sites for attachment
233
Focal Adhesions are _______-dependent attachments
integrin
234
Myosin-1's heaqd group is always walking towards the _________end of the actin filament
plus
235
In nonmuscle and smooth muscle, contraction is regulated primarily by ___________ of a myosin light chain
phosphorylation
236
Muscle cell contraction relies primarily on interaction between _______ & _______ filaments
thin; thick
237
What is the functional unit of contraction?
sarcomere
238
Each muscle fiber is a bundle of smaller ________
myofibrils
239
In muscle contraction, the head of a myosin-____ (1 or 2) molecule walks along an actin filament through a ATP dependent cycle of conformational changes.
2
