Final Topic 22 - Eukaryotes - Cytoskeleton Part 2

Question 1

Found in all eucaryotic cells

Answer 1

Actin Filaments

Question 2

Actin Filaments form:

Answer 2

1) Microvilli of intestinal epithelial cells
2) Small contractile bundles in cells
3) Dynamic protrusions of the motile cells
4) Contractile ring to separate cells during cell division

Question 3

Formed by polymerization of monomers

Answer 3

Actin Filaments

Question 4

2 filaments of actin monomers all of which point in the same direction

Answer 4

Twist around each other

Question 5

G-actin

Answer 5

Monomer

Globular Actin

Question 6

F-actin

Answer 6

Actin Filament

Question 7

Actin has

Answer 7

polarity

Question 8

(+) end

Answer 8

addition

Question 9

(-) end

Answer 9

Loss

Question 10

Actin can bind and hydrolyze

Answer 10

ATP

Question 11

ATP bound actin has a higher affinity to

Answer 11

Form a filament

Question 12

ADP-actin is more like to

Answer 12

Disassemble

Question 13

Promotes disassembly

Answer 13

Nucleotide hydrolysis

Question 14

Actin-ATP adds to ____ end and Actin-ADP then falls off the _____ end

Answer 14

(+)

-

Question 15

About half of actin in the cell is maintained as

Answer 15

G-actin

Question 16

Protein that binds to the G-actin monomer to keep it from polymerizing into F-actin

Answer 16

Profilin

Question 17

Regulates when and where the cell can make a filament

Answer 17

Profilin

Question 18

Actin polymerizes at

Answer 18

The (+) end

Question 19

Actin depolymerizes at

Answer 19

The (-) end

Question 20

Three main actin structures that cells use to move

Answer 20

1) Filopodium
2) Lamellipodium
3) Contractile bundles - actin and Myosin II (motor protein)

Question 21

Allow cells to move

Answer 21

Actin filaments

Question 22

Steps of cell locomotion

Answer 22

1. Actin polymerization at the lamellipodium pushes cell forward
2. The cell attaches the lamellipodium to the substrate through feet called integrins
3. Actin and Myosin II (actin motor protein) provide contractile forces to pull the cell forward

Question 23

Cell “feet”

Answer 23

Integrins

Question 24

Protein that binds to the (+) end of F-actin and promotes the addition of G-actin to the end of an unbranched filament

Answer 24

Formins

Question 25

Bind to the side of an existing actin filament and nucleate actin branching

Answer 25

ARP 2/3 Complex

Question 26

A family of actin-dependent motor proteins

Answer 26

Myosin

Question 27

Myosin bind and hydrolyze

Answer 27

ATP

Question 28

Myosin moves towards the

Answer 28

(+) end of the filament

Question 29

Has one actin binding ATPase head and one tail

Answer 29

Myosin I

Question 30

The main myosin protein in muscle

Answer 30

Myosin II

Question 31

Forms a dimer

Answer 31

Myosin II

Question 32

Two actin binding ATPase heads joined together by a coiled-coil tail

Answer 32

Myosin II

Question 33

Myosin II molecules cluster together through their tails into

Answer 33

Myosin Bipolar Filaments

Question 34

Muscle tissue is made up of

Answer 34

Muscle cells

Question 35

Multi-nucleated cells with cytoplasm of myofibrils

Answer 35

Muscle cells

Question 36

Cylindrical tubes that consist of repeating contractile units called sarcomeres

Answer 36

Myofibrils

Question 37

The basic contractile unit of the muscle

Answer 37

Sarcomere

Question 38

Actin filaments are anchored to the _________ at their _______ ends

Answer 38

Z disc | (+) ends

Question 39

The actin filaments face

Answer 39

Each other in the sarcomere

Question 40

Upon contraction, the myosin heads move

Answer 40

Towards the (+) end and pulls the actin filaments towards each other

Question 41

Myosin II Power Stroke

Answer 41

1. Myosin head is bound in nucleotide free form to actin 2. ATP binds to myosin and releases it from actin 3. Hydrolysis of myosin head changes the conformation of the head forward 4. Binding of the head to actin releases Pi 5. Release of ADP provides the conformational change to move the head backwards

Question 42

The use of ATP hydrolysis to move along the actin filament

Answer 42

Myosin head power stroke