Brainscape's Knowledge GenomeTM

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


See full index

Cell Biology > Week 10 > Flashcards

Week 10 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Gene involved in generating oscillations in the body’s day/night cycle

A

Per

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

Wnt pathway basic characteristics

A
  • Wnt from wingless in Drosophila and Int1 in mice
  • Secreted signaling molecule
  • Fatty acid covalently attached to their N-terminus, allowing them to bind to cell surfaces and create local gradients.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does Wnt signaling regulate?

A

Proteolysis of Beta-catenin

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

What happens to the B-catenin molecule in the Wnt pathway?

A
  • B-catenin is an important effector molecule in the signal pathway
  • Gets phosphorylated, ubiquitinated, and targeted for the proteosome.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Role of degradation complex in Wnt pathway

A
  • Keeps the proteins close and scaffolded to recruit kinases so necessary proteins (like B-catenin) can be degraded
  • In the presence of Wnt signal, the degradation complex is destroyed, so B-catenin is then in turn not degraded.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What protein must be activated to recruit Dishevelled in the Wnt pathway?

A

The Frizzled receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does Hedgehog collaborate with Wnt in development?

A

Different neuronal identities are dictated by the combination of Wnt and Hedgehog signaling experienced by each cell. How much of the two ligands (Wnt and Hedgehog) a neuron experiences will determine its fate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Four things that explain the real-life signaling dynamic observed in cells that a linear signaling pathway cannot capture

A
  1. Response timing
  2. Sensitivity
  3. Dynamic range
  4. Persistence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Response timing

A

Speed of a response

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

Sensitivity

A

Likelihood of a response to stimulus

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

Dynamic range

A

Range of stimulus intensity that a signaling pathway is sensitive to

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Persistence

A

How long a response persists after a transient stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does the speed of a response depend on?

A

The speed of a response depends on the turnover (half-life) of signaling molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Half-life relationship to decrease in synthesis rate

A

If stimulus triggers a decrease in synthesis rate of a signaling molecule, the drop in its relative concentration is quicker for molecules with short half-life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Half-life relationship to increase in synthesis rate

A

If stimulus triggers an increase in synthesis rate of a signaling molecule, the rise in its relative concentration is also quicker for molecules with short half-life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Relationship between sharpness of activation and number of effector molecules

A

Sharpness of activation increases with increasing number of effector molecules that must be simultaneously bound to the target protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Because four molecules of Ca2+ are required to activate one molecule of calmodulin, what type of response is this?

A

This results in a binary response (if only one Ca2+ ion were required, it would be a linear relationship. 1:1 ratio results in linear relationship)

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

When are all or none responses important?

A

All or none responses are important when a cellular decision needs to be permanent. E.g. apoptosis, cell fate

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

When is negative feedback useful?

A

Negative feedback can help prevent accidental activation of a signaling pathway due to background ‘noise’.

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

When is positive feedback useful?

A

Positive feedback loop can be used to sustain a response, even after the original signal is extinguished. In other words, it can be used to ‘remember’ the stimulus

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

Role of CaM-kinase II

A

CaM-kinase II acts as a ‘memory’ molecule, remaining active even after calcium signal decay. Involved in learning and memory

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

What happens after calcium binds to calmodulin?

A
  • Calmodulin binds to the linker region
  • Kinase is in popped out state, meaning it’s active
  • The kinase domain phosphorylates the linker region, keeping it in a popped out state
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How are oscillations related to Gq mediated IP3 production?

A
  • Gq mediated IP3 production releases calcium from ER in an oscillatory manner.
  • Calcium activates IP3 and ryanodine receptors on ER membrane at lows levels, but inhibits them at high concentrations.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Effect on calcium with increasing stimulation of vasopressin

A

The frequency, not the amplitude of the calcium spikes increases with increasing stimulation from vasopressin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What type of feedback generates the circadian clock?

A

Delayed negative feedback

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

With increasing stimulation from vasopressin, why does the frequency but not amplitude of the calcium spikes increase?

A
  • The negative feedback loops caps the amount of calcium allowed in the cytosol.
  • At a certain concentration, calcium will start to inhibit its own release, which means amplitude is capped at that concentration.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How does a delayed negative feedback loop generate the circadian clock?

A

After transcription and translation, Per forms a heterodimer with Tim (which is also transcribed and translated). Then the heterodimer will reenter the nucleus to inhibit Per and Tim. This is an example of a negative feedback loop because Per inhibits its own expression. Oscillations in the levels of Per and Tim generate the body’s circadian clock.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Role of DBT kinase

A

DBT kinase targets Per for degradation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Three major cytoskeleton filaments and main difference between them

A
  1. Actin filaments
  2. Microtubules
  3. Intermediate filaments
    Actin filaments and microtubules are asymmetric, while intermediate filaments are symmetric
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Structure of actin

A

Made of two protofilaments. Not as strong as microtubules which are composed of 13 protofilaments. Has a plus and minus end.

31
Q

What does the loss of subunits from the actin filament depend on?

A

The loss of subunits from the filament depends on the rate constant KOFF.

32
Q

What is the number of monomers that add to an actin filament per second proportional to?

A

But the number of monomers that add to the filament per second is proportional to the concentration of the free subunits (KONC).

33
Q

Critical concentration

A

As the filament grows, the concentration of free subunits (C) in solution drops until it reaches a constant value called the critical concentration (CC). At this concentration, the rate of subunit addition is equal to the rate of subunit loss.

34
Q

Equation that represents the steady state of an actin filament

A

when KONC = KOFF
the system is at steady state.
CC = KOFF/KON

35
Q

What event must occur for an actin filament to form?

A

In order for actin to grow, there must be a nucleation event in which a “seed” is created from which the actin filament can grow.

36
Q

Dynamics at plus vs minus end of actin

A
  • The dynamics at the two ends of the actin filament are different. The KON and KOFF at the plus end are higher than at the minus end.
  • However, the KOFF/KON ratio, and hence the critical concentration CC are the same.
37
Q

Rate of addition =

A

Kon C

38
Q

Rate of removal =

A

Koff

39
Q

When the concentration of the free subunits (C) is greater than Cc, what happens?

A

We know that filaments grow when the concentration of the free subunits (C) is greater than CC. But growth will be greater at the plus end than at the minus end.

40
Q

When the concentration of the free subunits (C) is less than Cc, what happens?

A

By the same token, when the concentration of the free subunits (C) is less than CC, filaments will shrink more rapidly at the plus end than at the minus end.

41
Q

Two forms of actin

A

T form: Bound to ATP
D form: Bound to ADP

42
Q

Stability of T vs D forms of actin

A

Filaments made with D form are more unstable than ones made with T form. In other words, Cc (D) > Cc (T)

43
Q

Free monomer subunits exist in which form?

A

T form, and then ATP gets hydrolyzed to ADP in the filament.

44
Q

What happens to filament growth when Cc(D) > [C] > Cc(T)?

A

Growth at the plus end and shrinkage at the minus end.

45
Q

Treadmilling

A

The process by which subunits are simultaneously added and removed from an actin filament. Assembly at the plus end and disassembly at the minus end.

46
Q

Role of formin

A

Nucleates assembly and remains associated with the growing plus end.

47
Q

Role of Arp2/3 complex

A

Nucleates assembly to form a branched network and remains associated with the minus end.

48
Q

Role of thymosin

A

Binds subunits, prevents assembly.

49
Q

Role of profilin

A

Binds monomers, concentrates them at sites of filament assembly.

50
Q

Role of tropomodulin

A

Prevents assembly and disassembly at minus end.

51
Q

How does nucleation affect filament growth?

A

Nucleation can eliminate the lag phase of filament growth, but it does not change the critical concentration

52
Q

How does the Arp2/3 complex affect the critical concentration?

A

Arp2/3 complex does not change the critical concentration—only helps with the seeding phase.

53
Q

How does the Arp2/3 complex provide stability to the actin filament?

A

By binding to the minus end, the Arp2/3 complex stabilizes the minus end and prevents disassembly at that end.

54
Q

How does the Arp2/3 complex create actin network?

A

Arp2/3 complex can bind to existing filaments, creating branched actin network. Binds at about a 70˚ angle.

55
Q

How are profilin and thymosin related?

A

Both regulate actin monomer availability, but they have opposite functions–profilin promotes filament growth while thymosin prevents it.

56
Q

How does profilin facilitate actin filament growth?

A

Profilin is a small molecule, analogous to actin subunits. It binds to three subunits in solution and brings them to the plus end of the filament.

57
Q

How do formins promote actin filamentation at the plus end?

A
  • Formin dimer captures two actin monomers and adds them to the actin filaments
  • OR another member of the formin protein family binds to profilin
58
Q

How does the type of formin with whiskers work?

A
  • The whiskers on the formin tether it to the plasma membrane, allowing the formin to bind to profilin, which will in turn bind to actin subunits.
59
Q

How is formin involved in cellular movement?

A

By having the formin tethered to the plasma membrane, it ensures the filament growth occurs near the membrane. This pushes on the membrane, pushing the cell forward.

60
Q

Effect of cofilin binding to actin filament

A

Cofilin binds along the length of actin filament, increasing the twist of the helical structure of the filament (shortens the turn).

61
Q

Cofilin binding preference

A

Cofilin has a preference for binding to subunits in the filament that are ADP bound. More preference for binding the minus end.

62
Q

What effect does cofilin binding have on filament assembly/disassembly?

A

Increasing the twist at the minus end promotes disassembly from the minus end.

63
Q

How do bacteria like Listeria take advantage of actin filaments in order to move?

A

Using the ActA protein, bacteria can highjack host cells’ actin cytoskeleton.

64
Q

How does the ActA protein work?

A
  • ActA recruits the Arp2/3 complex.
  • Arp2/3 then seeds growth of filaments.
  • When the filament grows, it pushes the cell forward.
  • Cofilin binds to the minus end and helps facilitate disassembly of the filament.
65
Q

AFM purpose

A

Stands for atomic force microscopy. Purpose is to measure force generated by mechanical movement of some object by protein of interest (actin in this case)

66
Q

How does AFM work?

A

An AFM cantilever with ActA localized near the tip is immersed in cell extract. As actin grows, it pushes on the cantilever, displacing it. That displacement can then be measured and the amount of force calculated.

67
Q

Myosin

A

Motors (all except myosin VI are plus-end motors) that attach to actin filaments

68
Q

The motor domain of myosin is at what terminus?

A

The N-terminus

69
Q

What role is myosin V important in?

A

Cargo transport.

70
Q

What role is myosin II important in?

A

Myosin II is used in skeletal muscles for contraction. It was the first motor protein identified and hence one of the most well characterized.

71
Q

How does myosin generate force?

A

Myosin hydrolyzes ATP to generate force.

72
Q

What type of experimental setup provides evidence for myosin motor activity?

A

A sliding filament assay

73
Q

What type of experimental setup measures the force of myosin motor activity?

A

An optical trap assay

74
Q

How does an optical trap assay work?

A

It uses light to catch and suspend beads in the air. Beads are attached via an actin filament. One bead is coated in myosin–the myosin head attaches to the actin filament, tugging on it.

Cell Biology (17 decks)

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