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Chapter12 How We Know: Squid Reveal Secrets of Membrane
Excitability
Studies on the squid giant axon were instrumental to our current understanding of
how action potentials are generated. You decide to do some experiments on
the squid giant axon yourself.
A.
B.
C.
You remove the cytoplasm in an axon and replace it with an artificial
cytoplasm that contains twice the normal concentration of K+ by
adding KOAc, where OAc– is an anion to which the membrane is
impermeable. In this way, you double the internal concentration of K+
while maintaining the bulk electrical balance of the cytoplasmic
solution. Will this make the resting potential of the membrane more or
less negative?
You add NaCl to the extracellular fluid and effectively double the
amount of extracellular Na+ ions. How does this affect the action
potential?
You replace half of the NaCl in the extracellular fluid with choline
chloride. (Choline is a monovalent cation much larger than Na+. Note
that the presence of choline will not impede the flow of Na+ through its
channels.) How will this affect the action potential?
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Chapter 15 How We Know: Tracking Protein and Vesicle
Transport
You have created a green fluorescent protein (GFP) fusion to a protein that is
normally secreted from yeast cells. Because you have learned about the use of
temperature-sensitive mutations in yeast to study protein and vesicle transport,
you obtain three mutant yeast strains, each defective in some aspect of the
protein secretory process. Being a good scientist, you of course also obtain a
wild-type control strain. You decide to examine the fate of your GFP fusion
protein in these various yeast strains and engineer the mutant strains to express
your GFP fusion protein. However, in your excitement to do the experiment,
you realize that you did not label any of the mutant yeast strains and no longer
know which strain is defective in what process. You end up numbering your
strains with the numbers 1 to 4, and then you carry out the experiment anyway,
obtaining the results shown in Figure Q15-66 (the black dots represent your
GFP fusion protein).
Figure Q15-66
Name the process that is defective in each of these strains. Remember that one
of these strains is your wild-type control.
自學:閲讀,200 字心得大意,一作業題
Chapter 16 How We Know: Untangling Cell Signaling Pathways
Figure Q16-63 shows how normal signaling works with a Ras protein acting
downstream of an RTK. You examine a cell line with a constitutively active Ras
protein that is always signaling. Which of the following conditions will turn off
signaling in this cell line?
Figure Q16-63
(a)
(b)
(c)
(d)
addition of a drug that prevents protein X from activating Ras
addition of a drug that increases the affinity of protein Y and Ras
addition of a drug that blocks protein Y from interacting with its target
addition of a drug that increases the activity of protein Y
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Chapter 17 How We Know: Pursuing Motor Proteins
Consider the in vitro motility assay using purified kinesin and purified polymerized
microtubules shown in Figure Q17-63. The three panels are images taken at 1second intervals. In this figure, three microtubules have been numbered to
make it easy to identify them. Which of the following statements about this
assay is false?
Figure Q17-63
(a)
(b)
(c)
(d)
Kinesin molecules are attached by their tails to a glass slide.
The microtubules used in this assay must be polymerized using
conditions that stabilize tubule formation or else they would undergo
dynamic instability.
ATP must be added for this assay to work.
Addition of the nonhydrolyzable ATP analog (AMP-PNP) would cause
the microtubules to move faster.
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Chapter 18 DISCOVERY OF CYCLINS AND CDKS
For each of the following sentences, fill in the blanks with the best word or phrase
selected from the list below. Not all words or phrases will be used; each word
or phrase should be used only once.
Many features of __________________ cells make them suitable for
biochemical studies of the cell-cycle control system. For example, the cells are
unusually large and are arrested in a __________________-like phase. When
the cells are triggered to resume cycling, the cell divisions have especially
__________________ G1 and G2 phases and occur __________________.
Studies with Xenopus eggs identified a partly purified activity called
__________________ that drives a resting Xenopus oocyte into M phase.
MPF activity was found to __________________ during the cell cycle,
although the amount of its kinase component, called __________________,
remained constant. The regulatory component of MPF, called
__________________, has a __________________ effect on MPF activity
and plays a part in regulating interactions with its __________________s. The
components of MPF are evolutionarily __________________ from yeast to
humans, so that the corresponding human genes are __________________ to
function in yeast.
able
hexokinase
short
asynchronously
inhibitory
sperm
Cdk
long
steady
conserved
M
stimulatory
cyclin
maturation promoting factor
substrate
divergent
oscillate
synchronously
egg
PI 3-kinase
ubiquitin
fibroblast
G1
G2
regulin
S
unable
uniform
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Chapter 20 How We Know: Making Sense of the Genes that are
Critical for Cancer
Your studies in cell biology have revealed how APC, a protein encoded by a tumor
suppressor gene that is frequently inactivated in people with colorectal
cancer, functions in the Wnt signaling pathway (see Figure Q20-64). This has
inspired you to study Wnt signaling. You would like to design a drug to treat
people with colorectal cancer. Given the pathway shown in Figure Q20-64 and
the knowledge that most human colorectal tumors harbor mutations in the
APC gene, name a protein from the pathway that would be a good target for
an activity-blocking anticancer drug. Explain your answer.
Figure Q20-64