Brainscape's Knowledge GenomeTM

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


See full index

Cell Biology > Cell Biology Chapter 5 > Flashcards

Cell Biology Chapter 5 Flashcards

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

Cytoskeleton

A

occupies large portion of cytosol and appears to link organelles to each other and to plasma membrane

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

The three elements/types of the Cytoskeleton

A
  1. Intermediate Filaments
  2. Microtubules,

3 Actin Filaments

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

Elements do not form mixed polymers

True or False?

A

True

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

Intermediate Filaments properties …

A

1(IFs) Are The Strongest, Most Stable Elements Of The Cytoskeleton

  1. Provides strength to the cell
  2. Typically stable polymers
  3. Wide variety enables cells to withstand many different types of forces
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The IF Genes in Humans Are Classified Into Six Groups. Name them

A

Class I - VI

70 IF genes form 75 different IF proteins

  • Alternative splicing
  • Largely tissue specific
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Characteristics of IF

A
  1. All IFs are only effective as a polymer
  2. Primary structure does not give tensile strength…essentially all strongs of amino acids have similar tensile strength in that form
  3. A central alpha-helical domain provides lots of tensile strength
    - Stablized by hydrogen bonds
    - Try to stretch it out  H-bonds prevent it from collapsing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Intermediate subunits form diamers

A

IF Subunits Form Coiled-Coil Dimers. Thus Tertiary Structure is illustrated

Homologous or Heterologous Assembly

Two alpha-helices form a coiled-coil
VERY STRONG STRUCTURE
Maximizes surface contact between two polypeptide chains
AKA a leucine zipper motif

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

coiled diamers now form…

A

antiparallel staggered structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

An Anti-parallel staggered tetramer assembly

A

Assembly is spontaneous and does not require input of energy

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

Why Post-translational modifications of IFs? …..

A

modifications control the shape and function of intermediate filaments

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

Phosphorylation-dephosphorylation

A

Phosphorylation dissolves lamin intermediate filaments in order to degrade the nuclear envelope during cell division

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

types of Post-translational modificat

A
  1. Glycosylation
  2. Farnesylation
  3. Transglutamination of head and tail domains
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lamins

A
  • Form a Cage Inside the Nucleus
  • Found exclusively in the cell nucleus
  • Three Lamin Genes in mammals undergo alternative splicing to produce 6 different Lamin subunits
  • A, B1, B2, B3, C1 and C2
  • Each cell contains at least one version of all three types (A,B,C)
    Specialized long helical domain distinguishes them from cytoplasmic Ifs, ensuring that they do not co-polymerize with shorter IF
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

IFs Form Specialized Structures

A

Largest and most diverse group of IFs are Keratins In Epithelium

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

Keratins In Epithelium

A
  • has Humans have 54 different genes
  • Obligate heterodimers (TypeI and Type II subunits) dictate differential developmental and expression patterns
  • Found in epithelial cell cytosol
  • Essential components in cell adhesion complexes such as hemidesmosomes and desmosome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Desmin

A

Desmin is Essential for Muscle Function

  • Desmin is a Type III IF that forms homodimers

Part of the contractile apparatus
- In Smooth muscle cells connects to actin filaments

  • In Skeletal and Cardiac Muscle is concentrated in the Z-lines of the sarcomere
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which statement about intermediate filaments is false?

A

A) When they are phosphorylated, they completely unfold to primary structure.
B) They have a core helical structure
C) Some form a protective layer on the inside surface of the inner nuclear membrane.
D) Phosphorylation of some causes dissolution of the nuclear envelope.
E) They are found in most eukaryotic cells.
Points Earned: 1.0/1.0
Correct Answer(s): A

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

What property of intermediate filaments makes them so resistant to tensile force (pulling)?

A

A) They contain more disulfide bonds than most other proteins.
B) They form coiled-coil dimers, which resemble strands in a rope.
C) They form filamentous polymers like other elements of the cytoskeleton.
D) They attach to hemidesmosomes.
E) They are not dissolved by most detergents.
Points Earned: 1.0/1.0
Correct Answer(s): B

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

Can microtubules form in the absence of γTuRC?

A

) Yes, they can spontaneously polymerize in a test tube

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

Costameres as a Desmin-containing Complex

A

Costameres link the contractile appartus to plasma membrane-localized receptors.

Mutations in costamere proteins (like desmin) can result in different types of muscular dystrophies

Costameres are ESSENTIAL for proper muscle function

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

Microtubules Organize Movement Within the Cell

A
  • Cells Can Sort and Direct its Contents
  • Stable Tracks
  • To a Destination
  • Energy-Dependent
  • Network Varies from Cell to Cell – No two cells are alike
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

MT cytoskeleton is a network

A

of “roads” for molecules “pass to and fro”

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

Microtubules – The Basics

A

Subunits called tubulin

Assembly requires a large complex of proteins and energy input

Microtubule-organizing Complex (MTOCs) called centrosomes can nucleate (initiate) the assembly of microtubules

  • Not found in plant cells
  • Found in most but not all animal cells.

MTOCs duplicate during S phase to form the two poles of the mitotic spindle during mitosis.

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

Which statement best describes an intermediate filament tetramer?

A

It consists of two overlapping, intermediate filament dimers arranged in a staggered orientation lacking structural polarity

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

Which observation best illustrates treadmilling by microtubules?

A

Which observation best illustrates treadmilling by microtubules?

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

The MTOC Contains

A

The Gamma Tubulin Ring Complex (γturc) That Nucleates MT Formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

cluster of centrosome proteins is called

A

Pericentriolar material

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

gamma (γ) tubulin

A

found in the Pericentriolar, its a protein organized into helical or ring shape. initiates the formation of microtubles

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

The Primary Building Block Of MTs

A

Is An Alpha-beta Tubulin Dimer

  • α- and β-tubulin bind together to form stable dimer
  • If purified α-β tubulin dimers bound to GTP are concentrated enough (critical concentration), they spontaneously form MTs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Which of the following exhibit treadmilling

A 
A) Microtubules 
 B) Microfilaments 
 C) Intermediate filaments 
 D) Answers A and B 
 E) Answers A, B and C 
Points Earned:	1.0/1.0	
Correct Answer(s):	D
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Three Properties of MT Assembly

A

1) MTs are only composed of two proteins: α and β tubulin.

2) Tubulin binds GTP.
α is married to its GTP (because it is hidden between the dimer), but β is not! β-bound GTP can be hydrolyzed to GDP and inorganic phosphate. The GDP can fall off and a new GTP can take its place.

3) Assembly is rapid, spontaneous and reversible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

MTs are hollow “tubes” composed of 13 protofilaments

A

1) Most short polymers dissasemble and are unstable
2) Some reach a critical size of 6-12 dimers and begin to grow
Polymers of dimers  sheet composed of 13 protofilaments  folds into a tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Three Important Differences Between in vitro and in vivo Microtubule Studies

A

1) MTs are seldom “alone” in cells and they do not all behave in the same way. MT-binding proteins regulate their stability
2) Every MT in a cell lies in its own unique environment – it is very heterogeneous as opposed to a test tube
3) Living cells don’t hold still and the internal state constantly changes so some variables are difficult to control in vivo.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

The Growth And Shrinkage of MTs Is Called

A

Dynamic Instability

Some microtubules rapidly grow and shrink in cells = dynamic instability

Elongation is at the + end by GTP-bound

35
Q

The growth of microtubules begins

A

The growth of microtubules begins at the gamma tubulin ring and continues as long as the plus end contains GTP-bound tubulin dimers.

36
Q

Catastrophe

A

What happens when the supply of GTP-bound tubulin dimers runs out?
1) MT depolymerizes at the + end
OR
2) Capping proteins prevent depolymerization

37
Q

Some MTs Exhibit Treadmilling

A

In cases where neither end of MT is stabilized, tubulin dimers are added to the + end and lost from the - end

Overall length of these MTs remains fairly constant, but the dimers are always in flux

38
Q

Benefits Of Dynamic Instability

A

Allows cells to have
flexibility with trafficking during cell movement
ability to exert force by bonding with cargo molecules
and to explore the cytosol

39
Q

MT-associated Proteins Regulate The Stability and Function of MTs

A

“MAPs” = capping proteins, rescue-associated proteins, and proteins that govern the motion
They can crosslink, bundle, or sever MTs also

Motor Protein = special type of MAP that transports organelles/vesicles
Dyneins and kinesins
Use ATP energy to accomplish this

40
Q

The Two Most Common Motor Proteins That Bind To Microtubules

A

Dynein And Kinesis

41
Q

How a microtubule motor protein moves along a microtubule.

A

Use ATP, release ADP

Dynesin to the negative end
Kinesin to the positive end

42
Q

Dynein

A

will travel towards the (-) of an MT

43
Q

Microtubule motor proteins transport pigment granules in a pigment cell

A

….like in a chameleon

44
Q

Vesicles are Carried in Two Directions Along Microtubules

A

…

45
Q

Specialized Microtubule-Based Structures Responsible for Motility in Some Cells

A

Cilia and Flagella

46
Q

Cilia and Flagella Are Specialized Microtubule-Based Structures Responsible for Motility in Some Cells

A

Microtubles can be used to generate external forces as well as internal forces
Cell swimming
In stationary cells, used to move fluid over the cell surface
Cilia and Flagella share a basic structure

47
Q

Axoneme

A

..

48
Q

Sliding Dynein =

A

Whip Movement

49
Q

Non motile cilium

A

In mammals, this forms on almost every cell.

It cannot “whip” like a normal cilium (lacks a central pair of MTs)

Plays a role in sensing external stimuli
Light
Odors

50
Q

Actin Filaments Control….

A

the Movement of Cells. (Not just movement within cells)

51
Q

Actin Filaments

A

Actin and its associated proteins greatly influence cell shape

Dominate in large-scale movements (like in muscle cells)

52
Q

The Building Block of Actin Filaments Is

A

The Monomeric actin protein. There are 6 different isoforms. (α, beta, gamma, lambda etc)

53
Q

Actin Filaments

A 
Smallest diameter of cytoskeletal filaments
7nm “microfilament” 
Great tensile strength
Structural polarity
(+) end = barbed end
(-) end = pointed end
Often bound to myosin
54
Q

The general structure of an actin filament

A

Figure 5-30 pg 172

55
Q

ATP binding/hydrolysis regulate actin filament polymerization and disassembly

A

Actin monomers, like tubulin, adopt two different shapes and each is determined by ATP (not GTP) bound to the monomer plus a single divalent cation (Mg2+, Ca2+ etc.)

+ ATP = polymerization
Hydrolysis of ATP = depolymerization
(ATPADP +Pi)

56
Q

Actin polymerization occurs in 3 stages. Draw & label

A

Figure 5-29 Pg. 172

57
Q

Actin filaments have structural polarity

A

Actin filaments undergo treadmilling

58
Q

Six Classes of Proteins Bind To Actin To Control Its Polymerization/Organization

MNCSDC

A

1 Monomer-binding proteins regulate actin polymerization eg. Proflin

59
Q 
#4 Severing Proteins
#6 Cross-linking proteins organize actin filaments into bundles and networks
A

Break actin filaments in the middle of the filament…

60
Q 
#5 Depolymerizing Proteins
Actin-Binding Motor Proteins Exert Force on Actin Filaments to Induce Cell Movement
A

Promote disassembly from ends of the actin filament
Actin depolymerizing factor (ADF) family
Cofilin
These motors provide ATP-mediated force
Potential energy converted to Kinetic energy
Bind-Move-Release-Shift cycle Like a Tug of War Line
More motors = More Force

Organization of primative body plans
Cell migration is essential for development
GI-tract cells are constantly replaced by cells migrating from the layer below
Intracellular trafficking

61
Q

Cell Migration

A

Actin-binding motor proteins exert force on actin filaments to induce cell movement
Cell migration is a complex, dynamic reorganization of an entire cell
Migrating cells produce three characteristic forms of actin filaments: filopodia, lamellopodia, and contractile filaments

62
Q

Three Characteristic Actin Formations

A

Lamellopodia, stress fibers, filopodia*

  • be able to identify
63
Q

Myosins

A

Are A Family Of Actin-binding Motor Proteins

64
Q

Contractile cycle

A

Myosins move towards one end of the actin filaments
Myosin V crawls towards the - end,
All other myosins crawl towards the + end
Allows for movement of cell

65
Q

Draw and label The contractile cycle of myosin.

A

..figure 5-37 pg 180

66
Q

The contractile cycle of myosin.

A

Cortical = outer edge of the cytosol
When myosins pull on these actin filaments, cell, it squeezes itself forward
Combined with waves of lamellepodia and filopodia and integrin complexes that pull on the actin filaments, the cell rolls and squeezes itself forward.

67
Q

Striated muscle contraction is a well-studied example of cell movement

A

..

68
Q

Eukkaryotic cytoskeletal proteins arose from prokaryotic ancestors

A

Modern prokaryotic cells express a number of cytoskeletal proteins that are homologous to eukaryotic cytoskeletal proteins and behave similarly
Vimentin (IF)
FtsZ (MT)
MreB and ParM (actin)
Shared properties seem to include protection of DNA, compartmentalization and motility

69
Q

What is the best explanation for why kinesin and dynein “walk” in opposite directions on microtubules?

A

Microtubules have structural polarity.

70
Q

If cell biologists use the term “GTP cap” when discussing microtubules, why don’t they use the term “ATP cap” when discussing actin filaments?

A

Actin filaments do not undergo dynamic instability in cells.

71
Q

Gelsolin is an actin filament severing protein. If you were to fluorescently label gelsolin in a migrating cell, where in the cell would it most likely be visible with a fluorescence microscope?

A

) In the rear of the cell

72
Q

Which one of the following properties of actin filaments makes them different from other cytoskeletal proteins?

A

They bind ATP.

73
Q

Intermediate filaments (IFs) are not used for intracellular transport of vesicles and organelles. Which statement best explains this?

A

) IFs have no structural polarity, and therefore cannot support directional movement

74
Q

The nucleotide __________ is required to form polymers of actin and the nucleotide ____ is needed to form polymers of tubulin

A

ATP, GTP

75
Q

Which of the following attributes of microtubules and microfilaments are also possessed by intermediate filaments?

A

A) They have structural polarity.
B) They require energy for polymerization.
C) They are involved with movement.
D) All of these attributes describe intermediate filaments.
E) None of these attributes describe intermediate filaments.
Points Earned: 1.0/1.0
Correct Answer(s): E

76
Q

Keratin, neurofilaments and lamins are associated with which cytoskeletal element

A

) intermediate filaments

77
Q

Axonemes and a 9+2 structure are found in

A

cilia and flagella

78
Q

Dyneins and kinesins move towards the ______ and _____end of a microtubule, respectively

A

minus, plus

79
Q

Filopodia and lamellopodia are associated with which cytoskeletal element?

A

microfilaments*

N/B not microTUBULES!!!

80
Q

The microtubule organizing center is composed of

A 
A) centrosomes 
 B) centromeres 
 C) chromosomes 
 D) centrioles 
 E) answers A and D 
Points Earned:	1.0/1.0	
Correct Answer(s):	E
80
Q

What does it mean to say Keratins are obligate heterodimers?

A

It’s filament must contain type I & type II subunits.

81
Q

Microtubules structure hierarchy

A

MTOC —> Centrosomes —-> centrioles —> pericentriolar —> gamma tubulins

82
Q

Motor proteins

A

Drag, pull cargo along microtubules. Use microtubules as roads.

83
Q

Draw & label Dynein & Kinesin

A

..

Cell Biology (7 decks)

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