Cytoskeleton

Question 1

3 types of protein filaments

Answer 1

Intermediate filaments
Microtubules
Actin filaments (also known as microfilaments)

Question 2

Intermediate filaments

Answer 2

Span cytosol and link adjacent cells at desmosomes
Give strength to animal cells- allow stretching
Form cell-cell junctions
10 micrometers diameter
Rope-like strands
Often associated with other proteins

Question 3

Keratins

Answer 3

Intermediate filaments in epithelia

Question 4

Vimentin

Answer 4

Intermediate filaments in connective tissue, muscle cells, and glial cells

Question 5

Neurofilaments

Answer 5

Intermediate filaments in nerve cells

Question 6

Nuclear lamins

Answer 6

Nuclear intermediate filaments in all animal cells

Question 7

Nuclear division

Answer 7

Phosphorylation of lamin (nuclear filament) causes lamina to dissemble

Question 8

Reassembly following telophase

Answer 8

Dephosphorylation of lamina

Question 9

Microtubule locations

Answer 9

Interphase cell: attached to centrosome
Dividing cell: mitotic spindles
Ciliated cell: attached to basal body

Question 10

Tubulin

Answer 10

Subunit of microtubules

Attach end to end, giving an alpha (minus) end and a beta (plus) end (polarity)

Question 11

Centrosome and microtubules

Answer 11

Microtubules grow from gamma-tubulin ring complex

Question 12

Polymerization of microtubules

Answer 12

Independent in each microtubule
Depends on tubulin-GTP availability
Dynamic instability: alternates between growing and shrinking
GTP-tubulin stabilizes the end of the microtubule, causing growth of microtubule
GTP hydrolysis: protofilaments containing GDP tubulin peel away from the microtubule wall and GDP tubulin is released into the cytosol

Question 13

Microtubule-specific drugs

Answer 13

Anti-cancer drugs (taxol, colchicine, vinblastine, etc.)
Bind and stabilize microtubules and subunits, preventing polymerization
Cell can’t divide, nervous system doesn’t work properly (microtubules allow transport along neurons)

Question 14

Capping proteins

Answer 14

Stabilize microtubules, resulting in polarization of cell

Question 15

Kinetochore microtubules

Answer 15

Connect to kinetochore (hold sister chromatids together)

Movement of cell parts based on motor proteins

Question 16

Microtubules and nerve cells

Answer 16

Establish polarity of nerve cells

Provide tracks for movement of cargo

Question 17

Dynein

Answer 17

Motor protein that uses microtubules as tracks for movement

Moves towards minus (alpha) end of microtubule

Question 18

Kinesin

Answer 18

Motor protein that uses microtubules as tracks for movement

Moves towards plus (beta) end of microtubule

Question 19

“Walking” of motor proteins by ATP hydrolysis

Answer 19

ATP binds
Hydrolysis
Release of ADP
Conformational change of motor protein, moving it forward

Question 20

Motor protein function

Answer 20

Transport of cargo

Vesicles with proteins destined for secretion or endocytosis, etc.

Question 21

Microtubules and ER and Golgi

Answer 21

Organization of ER and Golgi

Question 22

Cilium and flagellum cross section

Answer 22

9+2 array of microtubules: prevents sliding of microtubules

Dynein acts on filaments held together by nexin

Question 23

Roles of actin filaments

Answer 23

Maintenance of shape and contraction

Microvilli, contractile fibers, amoeboid movement, cell cleavage

Question 24

Microvilli

Answer 24

Actin filaments that increase surface area (don’t move)

Increased absorption

Question 25

Structure of actin filaments

Answer 25

Assemble with directionality | Plus end and minus end

Question 26

Actin filament polymerization

Answer 26

Can proceed from either end ATP bound actin binds to other actin particles Actin with bound ADP dissembles

Question 27

Protein interaction with actin

Answer 27

``` Critical for actin function Nucleating protein (control where actin binds), bundling protein (in filopodia), motor protein (myosin), capping protein, cross-linking protein (in cell cortex) ```

Question 28

Actin in the cell cortex

Answer 28

Gives cell cortex structure

Question 29

Amoeboid movement

Answer 29

Actin polymerization at plus end protrudes lamellipodium (finger-like projections) Myosin causes contraction at other end

Question 30

ARP complex

Answer 30

Branch point of actin filaments

Question 31

Actin-myosin mediated contraction

Answer 31

Moves membrane vesicles and allows contraction of membrane

Question 32

GTP binding proteins

Answer 32

Actin filaments respond to signaling by these

Question 33

Myosin-II molecule

Answer 33

Muscle myosin

Question 34

Contractile ring

Answer 34

Myosin-actin interaction | Cell division: pinching off of cells

Question 35

Contractile bundles

Answer 35

Myosin-actin interaction | Amoeboid movement

Question 36

Sarcomere

Answer 36

Contractile unit of muscle | Compose myofibrils which compose muscle cells

Question 37

Z disc

Answer 37

Anchorage of actin filaments in muscle

Question 38

Muscle contraction by ATP hydrolysis

Answer 38

Attachment: myosin head lacking a bound nucleotide is locked tightly onto an actin filament in a rigor configuration Release: molecule of ATP binds to back of myosin head and causes myosin to lose affinity for actin and move among the filament Cock: Head closes around the ATP molecule and hydrolysis of ATP occurs Force-generation: Myosin binds weakly to actin, causing release of phosphate produced by ATP hydrolysis Release triggers power stroke, moving myosin forward ADP is released, and myosin reattaches to actin

Question 39

Sarcoplasmic reticulum

Answer 39

Calcium storage in the muscle cell

Question 40

Transverse (T) tubules

Answer 40

Formed from invaginations of plasma membrane | Used for signaling in muscle cell

Question 41

Release of calcium in muscle cells

Answer 41

Depolarization of T-tubule membrane opens voltage gated calcium channel Ca+2 is released into cytosol and binds to calcium release channel of sarcoplasmic reticulum membrane, releasing calcium from sarcoplasmic reticulum

Question 42

Tropomyosin

Answer 42

Responds to calcium Attached to actin Normally blocks myosin-binding site, but when exposed to calcium, it moves, allowing myosin to move