Contractile Proteins

Question 1

Actin Bundles vs Actin Fibers

Answer 1

Actin bundles: closely packed, PARALLEL networks

Actin Networks: loosely cross-linked, Orthogonal arrays form 3D meshwork, FLEXIBLE

Question 2

An example of Actin bundles?

Answer 2

Microvilli

Question 3

Fimbrin:

Answer 3

molecule that binds actin filaments as MONOMERS

Question 4

Alpha actININ

Answer 4

binds actin as DIMER

allows for greater space, motor proteins have room to interact during contractions

Question 5

filamin

Answer 5

binds as dimers, 3D actin network

Question 6

Pseudopodia

Answer 6

crosslinked actin filaments for phagocytosis

Question 7

Lamellipodia

Answer 7

sheet extensions on leading edge

Question 8

Filopodia

Answer 8

formation and retraction of thin actin filaments to move cell

Question 9

Myosin

Answer 9

a superfamily of MOTOR proteins

move along actin fibers via ATP Hydrolysis

Question 10

Skeletal muscles are primarily composed of which type of myosin?

Answer 10

Type II, Bipolar (tails form shaft, heads at both ends)

Question 11

Myosin light chains bind to which section of the myosin?

Answer 11

The neck

Question 12

ATP and Actin bind to which section of myosin?

Answer 12

The myosin head

Question 13

The role of myosin tails

Answer 13

intertwine to keep myosin heads in close proximity

Question 14

Type I Myosin

Answer 14

membrane association, ENDOCYTOSIS

Question 15

Myosin Type II

Answer 15

Bipolar, muscle contractions

Question 16

Myosin Type V

Answer 16

Organelle Transport

Question 17

Muscle Contraction: Calcium is stored and released from

Answer 17

Sarcoplasmic reticulum

Question 18

Muscle Contraction: released calcium ions bind to?

Answer 18

Calcium ions bind to TROPONIN

Question 19

Muscle Contraction: Once calcium bind to troponin, _____ moves to expose ______

Answer 19

Tropomyosin moves to expose actin binding sites

Question 20

Muscle Contraction: Activated myosin binds to

Answer 20

Binds to actin binding sites

Question 21

Activated myosin:

Answer 21

ADP + Phosphate bound to myosin head (ATP has been hydrolyzed)

Question 22

Power stroke

Answer 22

ADP released from myosin head, causing myosin head to cock back, moving the muscle forward toward contraction

Question 23

Myosin head binds to Actin binding site after what?

Answer 23

After being activated, phosphorus leaves myosin head

Question 24

What causes myosin to unbind from actin?

Answer 24

Attachment of ATP

Question 25

Muscle continues to contract until what?

Answer 25

Until calcium is actively transported out of the sarcomere

Question 26

Deactivated myosin in smooth muscle

Answer 26

light chain myosin folds over on itself

Question 27

What causes Myosin-LC to unfold in smooth muscle?

Answer 27

Calcium binds to CAM, activating MLC kinase which phosphorylates myosin LC

Question 28

Phosphorylated myosin-lc

Answer 28

Active, unfolded, continual contraction of smooth muscle

Question 29

MLC Phosphatase

Answer 29

deactivates myosin-LC-P, myosin folds back on itself

Question 30

Example of actin use in non-muscle cells

Answer 30

actine-myosin contractile ring creates cleavage furrow in cytokinesis

Question 31

What type of myosin moves opposite of all other myosin?

Answer 31

Type VI (type six) moves from positive to negative

Question 32

Duchene MS

Answer 32

X-linked recessive
out-of-frame deletion causes muscle wasting due to the destruction of Dystrophin
Beckers MS is less severe in frame deletion

Question 33

Dystrophin

Answer 33

transfers energy stress from muscle contraction laterally and vertically. Defective in Muscular dystrophy