Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cell Biology > Chapter 14 > Flashcards

Chapter 14 Flashcards

1
Q

In another important transduction
cascade, Galpha activates which
enzyme?

A

Phospholipase C (PLC).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q 
In embryonic development, cells
secrete specific paracrine agents
that cause other groups of cells
to mature (differentiate) into
specific structures. What are
these paracrine agents called?
A

Morphogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q 
. In multicellular organisms, if a
cell secretes a compound that
affects neighboring cells of a
different cell type, what is it
called?
A

A paracrine agent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q 
. In multicellular organisms, if a
cell secretes a compound that
goes through the circulatory
system to affect distant target
cells, what is it called?
A

A hormone.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q 
Kd is the dissociation constant;
also known as the concentration
of ligand at which half of its
receptors are occupied. Will a
receptor with a high affinity for
its ligand have a high or low Kd?
A

A higher affinity
corresponds to a lower
Kd

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q 
Lots of things are triggered by
elevated intracellular calcium
levels (but not always due to the
IP3/DAG pathway). What are
these things?
A 
Skeletal muscle
contraction, release of
neurotransmitter, change
in the beat of cilia or
flagella, secretion of
hormones and saliva, and
zygote activation.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Most RTKs consist of a single
polypeptide chain that has the
following domains:

A 
Extracellular ligand
binding domain, single
membrane spanning
domain (an alpha helix), a
tyrosine kinase, and then
a cytosolic tail.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q 
. Nitric oxide is an
example of a gas
being used as a
messenger. What
kind of pathway does
this activate?
A 
Smooth muscle relaxation and blood
vessel dilation.
Acetylcholine -> receptor -> G-protein
-> PLC -> IP3 -> Ca release ->
Ca/calmodulin -> activates NO
synthase -> NO diffuses into
neighboring smooth muscle cells ->
activates guanylyl cyclase -> GTP is
converted to cGMP -> activates a
kinase -> smooth muscle relaxation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

. One huge class of
receptors is known
as what?

A

G-protein coupled receptors

GPCR’s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Paracrine agents
called growth factors
control what type of
cell behavior?

A

Cell division, migration, maturation

(differentiation), and survival.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Receptor tyrosine
kinases generally
bind to what types of
things?

A

Growth factors, protein hormones,

and morphogens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q 
Signal transduction
cascades usually
lead to amplification.
What is an example
of this?
A

One molecule of epinephrine releases
approximately 10^8 glucose-1-P
molecules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q 
Signal transduction
often entails a
diffusible, cytosolic
compound that elicits
the cell's response.
What is that protein
called?
A

A second messenger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q 
Since growth factors
control cell division,
and growth factors
work through RTKs,
mutations that affect
the transduction
pathway can lead to
what disease?
A

Cancer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q 
Some first
messengers are
lipophilic. What does
this mean for cell
signaling?
A

They can diffuse directly into the
target cells; second messengers are
not required.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q 
Transduction has one
common scheme.
Starting with two
RTK's binding their
ligands, what
happens after?
A 
The two RTK's bind ligands and
dimerize. They then phosphorylate
tyrosine residues on each other to be
activated and phosphorylate other
targets. This elicits a cellular
response.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are some
characteristics of NO
that make it ideal for
use as a local signal?

A

It is unstable and breaks down
quickly on its own. It is only for short
lived signals. It diffuses easily into
the cell without the use of receptors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

After G-proteins are activated, the next step is for the
alpha subunit to activate an enzyme in the membrane.
What is this enzyme called?

A

Adenylyl cyclase (or adenylate).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Aggregation of cellular slime molds under poor

conditions is mediated by what compound?

A

cAMP or Cyclic AMP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Both IP3 and DAG are second

messengers. Where do they go?

A

DAG stays in the membrane. IP3 is

released into the cytosol.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

cAMP binds to activate what?

A

Protein kinase A (PKA) and cAMPdependent

protein kinase A.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Cellular slime molds are now called

what?

A

Social amoebae.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Compounds that activate a receptor

are called what?

A

Agonists

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Drugs that block receptors are called

what?

A

Antagonists

25
Q

For elevated calcium levels to bring about these events,
it must be maintained at low levels otherwise. How is this
accomplished?

A
  1. Active transport to organelles (like the ER and
    mitochondria) .
  2. Outward transport out of the cell (secretion).
26
Q

Free calcium ion concentrations are

usually in what range?

A

Nanomolar (10^-9 to 10^-7).

27
Q

The frog eggs given the mutant FGF still were able to
make wild type FGF receptors with their own gene. How
could the mutant receptors interfere with the ability of the
normal ones to function?

A

When the wild type and mutant receptors are together

(dimerize), they can’t phosphorylate each other.

28
Q

GPCRs activate G proteins, which are

short for what?

A

GTP binding proteins.

29
Q

G-proteins are described as being

what? What does this mean?

A 
They are heterotrimeric, meaning they're made up of 3
different subunits (alpha, beta, and gamma).
30
Q

How can desensitization be brought

about?

A
  1. Phosphorylating receptors which lowers the affinity for
    its ligand (raises the Kd).
  2. Down-regulation or decrease of the number of
    receptors in the membrane.
31
Q

How does necrosis bring about cell

death?

A

After some kind of mechanical trauma, the membrane is
permeabilized (it can no longer exclude sodium),
therefore the cell bursts. This is called violent cell death.

32
Q

How does programmed cell death

work?

A

The cell actively kills itself.
The DNA condenses, cell forms blebs (protrusions), the organelles
fragment, and enzyme cleaves DNA at 200 bp intervals, the cell
then completely fragments and gets engulfed by other cells.

33
Q

How does Viagra work?

A

It blocks the phosphodiesterase that breaks down
cGMP, leading to an increase in that molecule that then
can activate the kinases that cause smooth muscle
relaxation.

34
Q

How is phosphorylation of RTK’s different

from phosphorylation of GPCRs?

A

Phosphorylation of RTKs activates them, while

phosphorylation of GPCRs desensitizes them.

35
Q

How many domains do GPCR’s have?

A

Seven hydrophobic domains.

36
Q

How would you characterize the

specificity of ligand binding?

A

It is specific and enzyme-like.

37
Q

If a cell is exposed to a constant concentration of first
messenger, what can happen to it? What is the term for
this?

A

It may lose sensitivity to it. It’s called

desensitization

38
Q

If a cell secretes a compound that affects the same cells

that do the secreting, what is the compound called?

A

An autocrine agent.

39
Q

If a pathway inhibits cell division, mutations that cause
cancer deactivate it inappropriately. What type of
mutation is this?

A

Loss of function.

40
Q

If a pathway promotes cell division, mutations that cause
cancer activate it inappropriately. What type of mutation
is this?

A

Gain of function.

41
Q

Inactivation of Galpha by GTP hydrolysis shuts off the
adenylyl cyclase. cAMP is broken down by what
compound?

A

Phosphodiesterase.

42
Q

What are the two main pathways that

lead to apoptosis?

A
  1. presence of an extracellular death signal (WBC
    sending out a signal for a cell infected by a virus).
  2. absence of survival growth factors (growth factors
    aka trophic factors).
43
Q

What are the two major routes of cell

death?

A

Necrosis and programmed cell death.

44
Q

What cascade does DAG begin?

A

DAG activates protein kinase C in the membrane, which

then phosphorylates enzymes and elicits a response.

45
Q

What cascade does IP3 begin?

A

IP3 opens the calcium channel in the sER, which leads to
it being released. Calcium then binds calmodulin, and
additional steps follow.

46
Q

What does adenylate do?

A

Convert ATP to the second messenger

cAMP.

47
Q

What does eutelic mean? What does

this mean for the nematode?

A

There is a constant number of cells within all organisms of the
same age. All adults within a sex have the same number of
somatic cells. All cells are named and their ancestries (lineages)
are known. 131 cells die via apoptosis to create the final adult
number.

48
Q

What does PLC do?

A

It converts the membrane lipid PIP2

into IP3 and DAG.

49
Q

What do kinases do?

A

Phosphorylate; they change enzyme activity through
covalent modification, in response to the first
messenger.

50
Q

What is preferable about apoptosis to

necrosis?

A

Apoptosis does not cause

inflammation like necrosis does.

51
Q

What is programmed cell death also

called?

A

Apoptosis

52
Q

What is the model organism for

apoptosis studies?

A

C. elegans nematode.

53
Q

What is the process of apoptosis for a cell in the

presence of extracellular death signals?

A

The cell that is infected by a virus comes across a killer lymphocyte. The
lymphocyte has proteins that bind to the infected cells CD95. The CD95s
aggregate and adaptor proteins attach. The adaptor proteins cause initiator
procaspase to aggregate and they get activated to caspases. A cascade results,
and effector/executioner caspases chop up all sorts of things.

54
Q

What is the process of apoptosis for

cells lacking trophic factors?

A

Some members of the Bcl-2 family of proteins promote apoptosis, others inhibit it.
They balance each other at the mitochondrial outer membrane. Usually those that
inhibit apoptosis are at the membrane, and those that promote it are in the cytosol.
The absence of trophic factors causes the pro-apoptic proteins to move to the
mitochondrial membrane, shifting the balance at the mitochondrion. The
mitochondria then releases cytochrome C, and the cyt c activates caspases

55
Q 
What is the signal cascade for a
signaling molecule (ligand)?
A

Signaling molecule –> first messenger –> receptor
protein –> biochemical cascade (signal transduction
cascade) –> response of cell

56
Q

What kind of responses may be

elicited by second messengers?

A
  1. Enzyme phosphorylation (activate/deactivate them
    within the cell)
  2. Change in gene expression
57
Q

What was an experiment that showed the importance of

growth factors in embryonic development?

A 
Injecting frog eggs with mRNA of mutant fibroblast
growth factor (FGF) receptors; no tail developed.
58
Q

What would happen if a cell couldn’t respond to a growth
factor that inhibited cell division, or acted as though a
growth factor that promotes cell division was present
when it actually wasn’t?

A

The cell would divide unregulated and

perhaps cause a tumor/cancer to form.

59
Q

When does apoptosis occur?

A

During the normal turnover of cells, and at points in
development (loss of webbing, metamorphosis, and
extra neurons dying).

Cell Biology (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions