contractile proteins

Question 1

What are the two general structures of actin -based filaments?

Answer 1

Actin bundles and actin networks

Question 2

What are actin bundles?

Answer 2

a cross-linking of actin into closely packed parallel arrays

Question 3

What are actin networks?

Answer 3

loosely cross-linked actin filaments into orthogonal arrays that form three-dimensional meshwork with gel-like properties

Question 4

What is a parallel bundle?

Answer 4

an actin bundling type that are closely associated actin fliments in parallel attached by fimbrin- they are generally found in microvilli

Question 5

What is a contractile bundle?

Answer 5

An actin fliament that is loosely associated- they are generally crosslinked by alpha-actinin- they are separated by a greater distance

Question 6

What is filamin?

Answer 6

binds actin into a dimer that can become a three dimensional meshwork

Question 7

Where are three dimensional actin networks generally found?

Answer 7

in association with the plasma membrane generally

Question 8

what is the name of actin binding proteins in erythrocytes?

Answer 8

spectrin- a tetramer that is associated laterally

Question 9

What is hereditary spherocytosis?

Answer 9

A mutation in the cortical cytoskeleton of erythrocytes- degrades the flexibility of the cell and will lead to anemia, jaundice and abnormal RBC

Question 10

what is a psuedopodia?

Answer 10

actin filaments that are cross-linked into a three dimensional network that are responsible for phagocytosis

Question 11

What is a lamellipodia?

Answer 11

a broad, sheet like extension at the leading edge of the cell, containing a network of actin filaments

Question 12

What is a filopodia?

Answer 12

thin projections of the plasma membrane supported by actin. The formation and retraction is based on the assembly and disassembly of actin

Question 13

What is myosin?

Answer 13

a superfamily of motor proteins- ex is in skeletal muscle- myosin II

Question 14

What are the three major domains of myosin? what is the structure/function of these domains?

Answer 14

The head- actin/ATP binding sites that have ATPase activity
The neck- flexible region that binds the light chains
The tail- intertwined to bring heads in close proximity and will bind to membrane or organelles

Question 15

What does myosin heads generally bind to?

Answer 15

ATP will enduce a confirmational change that will disassociate myosin from actin

Question 16

What will determine the velocity of the powerstroke?

Answer 16

The length of the neck on the myosin filament- a longer neck will mean an increased rate of movement

Question 17

What myosin is involved with vesicular transport?

Answer 17

myosin V

Question 18

What is disrupted in duchennes muscular dystrophy?

Answer 18

The dystrophin-glycoprotein complex that provides a structural link between the cytoskeleton of the muscle cell that the ECM- will stabilize the sarcolemma to prevent rupture of the cell