Ch. 17 - The Cytoskeleton

Front 1

Cytoskeleton Functions

Back 1

Structural Support
Organization
Intracellular/Extracellular Movement

Front 2

Rho

Back 2

monomeric GTP binding protein that rearranges actin filaments

Front 3

Microfilaments

Back 3

Smallest
made of actin (globular protein)
dynamic

Front 4

Intermediate filaments

Back 4

medium
made of variety of proteins
scaffolding
not dynamic. Great tensile strength.

Front 5

microtubules

Back 5

largest
made of alpha and beta tubulin
found in dimers
dynamic

Front 6

Structure of intermediate filaments

Back 6

one alpha helix with globular N-terminus and C-terminus.
Two monomers->dimer->tetramer

Front 7

what part of the alpha helix is used for differentiation?

Back 7

the alpha helix

Front 8

Where are intermediate filaments anchored?

Back 8

desmosomes (cell-cell junctions)

Front 9

Which cells are intermediate filaments prominent in?

Back 9

neurons, epithelial and muscle

Front 10

What is the nuclear lamina made of?

Back 10

Lamin proteins (type of intermediate filaments). They have to dissociate in mitosis

Front 11

What is progeria?

Back 11

Defects in the lamin protein.

Front 12

Categories of intermediate filaments

Back 12

keratin
vimentin
neurofilaments
nuclear lamins

Front 13

Where are keratin filaments found?

Back 13

Epithelial cells

Front 14

How do keratin proteins attach cells?

Back 14

desmosomes

Front 15

Epidermolysis bullosa simplex

Back 15

Mutation in keratin genes that makes them highly sensitive to injury

Front 16

What aid in the biding of intermediate filaments?

Back 16

Plectin proteins

Front 17

What are the functions of microtubules?

Back 17

Anchor organelles
Provide tracks for motor proteins
Segregate chromosomes during mitosis
make up cilia and flagella

Front 18

Protofilament

Back 18

When alpha and beta dimers link together

Front 19

How many protofilaments make up one microtubule?

Back 19

13 protofilaments

Front 20

What do microtubules grow from?

Back 20

Centrosome
Spindle Pole
Basal Body of Cilium

Front 21

What forms the nucleation site of an intermediate filament?

Back 21

Gamma tubulin

Front 22

Which direction does tubulin grow?

Back 22

From negative to positive

Front 23

Which end do the microtubules grow rapidly at?

Back 23

The positive end

Front 24

How does a microtubule grow/shrink?

Back 24

When bound to GTP, it grows. When bound to GDP, it shrinks.

Front 25

How are microtubules stabilized?

Back 25

When the plus ends make contact with other molecules or cell structures

Front 26

What is cell polarization?

Back 26

Something binding to the plus end to prevent depolymerization

Front 27

What is the structure of a motor protein?

Back 27

Dimer (carries cargo) with 2 globular heads that "walk" across the microtubule via ATP hydrolysis

Front 28

How does the motor protein walk across the microtubule?

Back 28

ATP. Hydrolysis. Movement is via conformational changes.

Front 29

Which cystoskeletal filaments do motor proteins interact with?

Back 29

Actin filaments and microtubules

Front 30

Kinesin

Back 30

Move toward the plus end

Front 31

Dyneins

Back 31

Move toward the negative end

Front 32

What is the structure of Kinesin/Dyneins?

Back 32

Dimers. Each dimer has a head and a tail.

Front 33

Cholchicine

Back 33

Drug that disassembles microtubules and causes organelles to change location

Front 34

Cilia

Back 34

Hair like projections
Made of microtubules
Propel organisms or move fluid

Front 35

Flagella

Back 35

Made of microtubules
Wavelike motion

Front 36

What is the structure of cilia/flagella

Back 36

9+2 arrangement of microtubules.

Front 37

How are microtubules connected?

Back 37

Ciliary dynein

Front 38

What causes movement of microtubules?

Back 38

The movement of outer microtubules (9) in relation to the 2 inside. Causes bending and sliding. Sliding uses ATP

Front 39

Kartagener's Syndrome

Back 39

Hereditary defects in ciliary dynein
Effects: brochiole infections and infertility

Front 40

Actin Filaments Function in?

Back 40

Cell crawling
Phagocytosis
Cell division

Front 41

Structure of Actin

Back 41

made from actin monomers. Have a plus and minus end. Found in bundles and networks.

Front 42

How is Actin stabilized?

Back 42

By ATP. Actin is more stable when bound to ATP.
ATP hydrolysis favors depolymerization

Front 43

What controls the behavior of actin binding filaments?

Back 43

Actin-binding proteins

Front 44

What is the cell cortex?

Back 44

meshwork of actin filaments that extend into the cytoplasm

Front 45

What is the cell cortex responsible for?

Back 45

locomotion and cell shape changes

Front 46

How does actin move a cell forward?

Back 46

Leading edge protrusions in the front make contact with the surface that it is crawling on. The rear (made of myosin) contracts and releases, pushing the cell forward.

Front 47

Lamellipodia

Back 47

thin, sheetlike, branched of actin

Front 48

filopodia

Back 48

thin, stiff protrusions of actin

Front 49

What promotes branching of the actin?

Back 49

actin related proteins (ARPs)
example: Lamelipodia

Front 50

What promotes unbranches formation of actin?

Back 50

formins (Clamp) on the plus end

Front 51

What help anchor the actin to the ECM?

Back 51

Integrins

Front 52

How do integrins function?

Back 52

They attach to proteins in the ECM or whatever it is crawling on, and attaches to actin inside the cell.

Front 53

What does actin associate with to form contractile structures?

Back 53

Myosin

Front 54

Which direction do Myosin move in?

Back 54

From negative to positive (along the positive end) via ATP hydrolysis

Front 55

What are the sub-families of Myosin?

Back 55

Myosin 1 and Myosin 2

Front 56

Which sub-family of Myosin is prominent in muscle cells?

Back 56

Myosin 2

Front 57

What is the structure of Myosin 1?

Back 57

Head: Binds to Actin
Tail: Binds to cargo or something else
Movement is energy dependent

Front 58

Which protein is directly related in change of actin filament organization?

Back 58

The Rho protein family

Front 59

What is the structure of Myosin 2?

Back 59

Two ATPase heads
One dimer tail

Front 60

How does Myosin 2 aid in muscle contraction?

Back 60

Myosin 2 tails cluster into coiled coils->bipolar myosin filament with heads in opposite direction->head bind to actin->pull in opposite direction->muscle contracts

Front 61

What is skeletal muscle cytoplasm composed of?

Back 61

Myofibrils

Front 62

What are myofibrils made of?

Back 62

sarcomeres

Front 63

What are sarcomeres?

Back 63

long chain of contractile units of myosin and actin that make up a myofibril

Front 64

How is muscle contraction signaled?

Back 64

Nerve impulse->neuron->depolarization->T-tubules->opening of Ca in the sarcoplasmic reticulum

Front 65

What does tropomyosin do?

Back 65

Interacts with actin and prevents it from binding to myosin

Front 66

What reacts with tropomyosin?

Back 66

Troponin

Front 67

How does calcium cause muscle contraction?

Back 67

Ca->binds to troponin->shift in tropomyosin->allows myosin to bind->muscle contracts