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Flashcards in Cytoskeleton and Cell Membrane Deck (67):
1

List the three specific types of structures found in the cytoskeleton.

1. Microfilaments
2. Intermediate filaments
3. Microtubules

2

Microfilaments are made up predominately of _____

actin

3

Characteristics of Actin Filaments

7 nm thick, bind to specific transmembrance proteins either directly or indirectly. Exist as monomers and long chains

4

Actin monomers are called:

g-actin

5

Actin long chains are called:

f-actin

6

Taxol will NOT inhibit microtubular polymerization

True

7

Nuclear lamins are intermediate filaments that:

Line the inner aspect of the nuclear envelope.

8

____________ initiates growth of f-actin from the sides of existing filament and causes branching

Arp2/3

9

fibronectin is NOT a type of intermediate filament

True

10

Low concentrations of G-actin ________ the disassembly of actin filaments

Favor

11

A dynamic equilibrium is favored when _____________ concentrations of g-actin are present

intermediate

12

Net addition at both ends of the actin filament are favored when the G-actin concentration is ___________

Higher

13

Cytochalasins are actin binding proteins that:

bind to the barbed (plus) end and block elongation. They can also inhibit movements, such as mitosis

14

Actin-binding protein, Phalloidin:

binds to the actin filaments and prevents dissociation. It can be labeled with fluorescent dyes for visualization

15

Actin-Binding Protein, spectrin:

Is found in RBCs. It binds coritcal cytoskeleton to plasma membrane

16

Actin-Binding Protein, Dystrophin:

Binds cortical cytoskeleton to plasma membrane. Muscle tissue related

17

Actin-Binding Protein, Villin and Fimbrin

cross-links microvilli. Links to actin chains

18

Actin-Binding Protein, Calmoduling and myosin I:

cross-links actin to plasma membrane in microvilli

19

Actin-Binding Protein: alpha-actinin:

cross-links stress fibers and connects actin to protein-plasma membrane complexes.

20

Actin-Binding Protein, Filamin:

Cross-links actin at wide angles to form screen-like gels.

21

Thymosin:

controls treadmilling, captures actin monomers and prevents actin monomers form being polymerized

22

Profilin:

Bind to actin monomers and prevent monomer from being polymerized. Facilitates exchange of bound ADP for ATP- which favors polymerization. Remember, only ATP-actin monomers can be assembled into f-actin.

23

Gelsolin:

Treadmilling control; destabilizes f-actin and caps actin filaments, preventing loss and addition of g-actin. In presence of calcium ion, fragments actin filament and remains bound to the plus end.

24

Cofilin:

Triggers depolymerization of ADP-bound actin at the minus end.

25

Arp2/3:

Initiates growth of F-actin from sides of existing filament-- causing branching.

26

________ and __________ complex determine where filaments (branching) are formed by facilitating nucleation

Fromin, Arp2/3

27

Tropomyosins:

Stabilize the actin filaments that are nucleated by Formins

28

Name the three proteins that are not naturally ocuring in the cell be can be added to effect actin polymerization

cytochalasins, phalloidin, latrunculins

29

Latrunculins:

come from Red Sea Sponge. Bind to g-actin and induce f-actin depolymerization

30

Name the two types of actin bundles:

Parallel Bundles and Contractile Bundles

31

Parallel bundles:

an actin bundle that has closely spaced actin filaments aligned in parallel, all with the same polarity, with the barbed ends adjacent to the plasma membrane.

32

Contractile Bundles:

actin bundles that are more widely spaced filaments, cross-linked by alpha-actinin. The increasing space allows the motor protein myosin to interact with the actin filaments.

33

Phalloidin:

Prevents depolymerization by binding to actin filaments

34

Intermediate Filaments.....

1. Provide tensile strength in cells such as neurons and muscle.
2. Are abundant in cells subject to mechanical Strength
3. Strengthen epithelial cells as desmosomes and hemidesmosomes
4. All have a common monomer consisting of central alpha-helix rod flanked by head and tail domains.

35

The rodlike portion of intermediate filaments.....

1. Consists of repeated amino acid segments (heptads)
2. Facilitate formation of coiled-coil-a-helix dimers or parallel intermediate filament proteins.

36

_______ and ______ terminals for the rodlike proteins (intermediate filaments) form links to other cytoskeletal elements.

Carboxyl, Amino

37

Explain Intermediate filament assembly

you have two antiparallel dimer form a staggered tetramer. The non-polar tetramers bind end-to-end and for a helical filament. This spontaneous formation does not require ATP or GTP

38

Intermediate Filament Associated Proteins (IFAPS)

Stabilize filaments by cross-linking adjacent filaments or by linking to other cytoskeletal elements, and may cap filaments to prevent further elongation.

39

List the five IFAPs

Filaggrin, epinemin, paranemin, plectin, synemin.

40

Type I Intermediate Filament

Acidic Keratins: with type II these for the intermediate filaments of the epithelial cell cytoskeleton. Associated with plaques of desmosomes and hemidesmosomes

41

Type II Intermediate Filament

Neutral to Basic keratins.

42

Type IV Intermediate Filament

Neurofilaments: found in axons and dendrites

43

Type V Intermediate Filament

Nuclear lamins: Provide mechanical support for inner membrane of nuclear envelope and bind chromatin

44

Type VI Intermediate Filament

Nestin: associated with CNS stem cells

45

Microtubules

are composed of tubulin dimers, alpha and beta units. Have a dynamic instability

46

Microtubules consist of ___ ________ arranged parallel to form a cylinder with a hollow core.

13 protofilaments

47

The microtubule plus end grows more rapidly than the minus end in presence of _________ [ ]

low calcium ion

48

Define MAPs

Microtubule-associated proteins

49

Protofilaments are longitudinal rows of.....

Tubulin dimers

50

Factors that inhibit microtubule polymerization

colchicines- arrest in metaphase to photograph karyotypes. Colcemide. Vincristin and vinblastin are anti-cance drugs

51

Factors that stabilize microtubles

Taxol- binds to MTs to prevent depolymerization. Disrupts mitosis

52

Structure of Cilium

9+2 config. 9 peripheral doublets + central pair of microtubules. Each doublet consist of the alpha tubule and Beta tublue

53

Explain the alpha and beta tubule of cilium doublets

Alpha: Consist of 13 profilaments, radial spokes extending to sheath around central pair, Pairs of dynein arms projecting to beta unit of next doublet

Beta: 10-11 protfilaments

54

What is a protofilament?

a vertical linear array of tubulin units alpha and beta alternating along its length.

55

List some functions of the cytoskeleton

cell movement, spindle formation and function, support and strength for the cell, phagocytosis, cytokinesis, cell-to-cell and cell-to-ECM adherence, changes in cell shape, intracellular transport.

56

Outer leaflet of phospholipid bilayer contains....

cholesterol, phosphotidylcholine, sphingomyelin

57

inner leaflet of phospholipid bilayer contains....

cholesterol, phosphotidylethanolamine, phosphatidylserine (-), phosphatidylinositol (-) and important in cell signaling.

58

Glycolipids:

are found only in the outer leaflet with carbohydrate portion facing the extracelluar environment.

59

Cholesterol:

within the phospholipd bilayer, moderates membrane fluidity. At high temp it interferes with FA chain movement making outer part less fluid reducing permeability to small molecules.

At low temp it prevents membranes from freezing and maintains membrane fluidity.

60

Glycocalyx:

Not an integral part of membrane. Carbohydrate coat on the extracellular surface of cell membrane composed of carbohydrate portions of glycolipids and glycoproteins.

61

Lipid Rafts

small patches of: cholesterol and sphingolipids (sphingomyelin and glycolipds)

62

Peripheral Proteins:

are found on both the inner and outer leaflets of the cell membrane facing either the extracellular or intracellular fluid. Can be removed by altering pH or ionic content of environment

63

Integral Proteins:

Embedded within the phospholipid bilayer, extracellular portion is typically glycolsylated. These proteins can only be removed by detergents.

64

Transmembrane proteins;

Integral proteins that pass completely through both phospholipid layers, typically server as channel and transporter proteins and must have at least one hydrophobic and two hydrophilic domains. i.e glycophorin and band 3

65

Glycophorin and Band 3 are examples of what?

transmembrane proteins.

66

Single pass transmembrane proteins:

have single hydrophobic domain that passes through the bilipid layer only once. Includes enzyme linked receptors and glycophorin

67

Multiple-pass transmembrane proteins

multiple passes through the cell membrane using two or more hydrophobic domains. Typically activated by the addition of a phosphate. Includes g-protein-linked receptors (7 domains), and larger transporter proteins and channel proteins. Porin has 12 domains.